Fox T-Bird/Cougar Forums

On and off for some time I have been trying to get to the bottom of the high range coolant temp needle on the dash.  I have addressed much of everything on this problem.  For years before 2007, this Tbird gauge would only measure in the low end of the scale in all conditions--now it's been the opposite.  Today I just replaced the thermostat (now 195 F ; was 193 F) and replaced the temp sensor directly above the thermostat--fitted with a push on wire.  Seems there are two on this engine?  The other is closer to the distributor cap and has a pinched type plastic type connector mounted on it- two wire.  I have now replaced both.  The engine cold starts and before the radiator can even get hot, the needle already is where the pic shows.  It pretty much stays there and even creeps up at times -being near the red hash mark if I am stopped.  The antifreeze isnt new but I have driven with aged antifreeze in many cars without any problems over the years.    ??  I see no sign of head gasket problems either.

You need to warm up the engine and measure the resistance of the 1 wire sender to ground, then measure voltage there on the red/white with it disconnected. You're looking for 5 volts. Reconnect with the engine still hot, pull the cluster and measure resistance to ground on R/W again, compare to the resistance reading you took directly off the sender (you may want to re-measure at the sender at that time just to be safe).  The allowable variation is low, the sender measurement should be within .2-.5 ohms.  If it specs out the same as the sender you need a cluster, if not, you need to measure resistance of the circuit (with the key off and out) which SHOULD be .2 to .5 end to end, but if we're at this step, you'll likely find much more.  Dive in after the source of the high resistance, repair as necessary.

Thefoeyouknow----  Thanks for the technical reply as you put some effort into it and I appreciate the diagram.  All other components on this vehicle appear normal----
I will have to digest this info and decide whether I can play electrical tech to the level you have subscribed me to!!!  I do have a vom.  Fortunately, I have taken the cluster out before, twice--to replace a bulb.  That was 10+ years ago.  Amazing how that is---once you get past a bunch of burned out bulbs at about 10-15 years old, the rest hang in there forever!

i would venture to say you should be paying attention to the wire called the "un insulated" wire ~the resistance wire.

its a small gray wire on your ign switch , if you skin it back its a single solid conductor  but no need to skin it.
with the cluster out, measure the resistance from the instrument cluster connector to the ign switch. 

maybe for you it would be easier to swap in a different cluster to verify if its "car" or "cluster".  These clusters are easy to get your hands on.
the IVR is making the voltage out to the guage, if the resistance wire is over heated at the ign switch , i will effect your fuel and temp guage.

having trouble being 100% sure your fuel guage is actually correct?  do you seem to hit totally empty when the needle hits "E"?
does your fuel guage seem to read way higher than "F" and hold there for an unusual period of time say 150miles then quickly drops to 1/2 in like 40 to 50 miles?

jcassity:  "having trouble being 100% sure your fuel guage is actually correct? do you seem to hit totally empty when the needle hits "E"?
 does your fuel guage seem to read way higher than "F" and hold there for an unusual period of time say 150miles then quickly drops to 1/2 in like 40 to 50 miles? "

Interesting question----this was the Mrs car from Jan 1988 to April 2008.  She has always commented that the gas needle had a characteristic quick drop once it started to move off full--particularily when less than 1/2.    When the tank is filled completely, the needle is moved some distance beyond the Full mark and freezes there until maybe 4 gallons are gone(and this is a guess). The gas gauge on this TBird is like the old VW Beetle--which had a similar action (for those of those who drove air cooled beetles pre 1972).  Not sure on the empty--we tried always to avoid that scenario, but it seemed to have the magical "Reserve" like the old VW.  The VW, tho, had a specific marking on the gas gauge showing that.  Empty happened once in our driveway (luckily) and I cant remember the needle.  I probably could fill the tank and shoot a pic of the needle.  Overall, the gas gauge presentation has not changed in 24 years on the TBird.  The big question for all --is this the designed activity for the car and not a fault?

Another thought based on your comment was the ignition switch.  This car had a recall and the switch was replaced in 1994 (Long ago...).    In 2005, I removed the lock cylinder to file a burr on it.  The burr was causing the keyswitch to seize in some positions--very annoying.  I ended up doing that on the 2 Fords we have and the problem was solved.  I dont remember the work but I dont believe the repair relates to any electrical problem I could have caused there--as I dont believe any wiring except the key gong warning (door open) was involved?  BUT?

Absolutely yes. That's how they are. I fiddled around with mine for a couple of months on and off. My car would not move off of the red E hatch until 6-8 gallons were in the car. It was a 21 gallon tank and it would still go above full when I stopped at the pump. I tried 2 sending units, and a different gas tank. Same problem. Next time you fill it up, run it down to the red "E" area. Make note of how many gallons you've added. If it's 15-16, you'll know when on E, you still have quite a ways you can go. Not that I recommend it though.

Today I topped the tank--although I recall similar results over the years--when you pay attention it does seem odd.  If you see the gauge in the above pic, now it looks like the pic here, but it took 10 gallons to go that short distance!!  The book says the tank is 22.1 gallons.  I recall testing the matter and having the needle on E and we filled it 20 gallons.  So the car has a 2 gallon cushion--(now that I thought about it and see jpc647's comments above, I do recall learning this some time ago).  I drove the car today in 90 F heat at 6 pm--varying speeds up to 45mph and had no problem other than the gauge is the way it is now.  I will consider getting a cluster if it is inexpensive--you just dont see many 80's T-birds around here anymore.  I'll have to check the bone yards.

You have a bad 5V regulator. They go bad all the time.  Easiest way to determine this is BOTH GAUGES READ HIGH. To further check but i dont know why you would it is totally clear the gauges are over voltage. You can put a standard test light from ground to the removed temp lead and key the ignition. If the light pulses the regulator is OK if not it will stay steady. Those regulators go bad all the TIME. I loved the answer FOE gave FASCINATING AT BEST!! 

http://www.ebay.com/ctg/Standard-Motor-Products-VRC606-Instrument-Cluster-Voltage-Regulator-Switch-/76715898

NOTE you can carefully remove the cover and burnish the contacts on your unit. Then replace the cover. Normally the contacts fuse together. I have fixed many of these in my career. Or they sell electronic ones that work much better. One other thing. If you key the car and the gauge goes up smoothly the regulator is shot. If the gauge goes up with a slight pulsing motion the regulator is OK. This is a simple test that i do to see if the regulator is BAD!!! This can be dun right in the drivers seat. Key the car and watch the fuel gauge for slight needle pulses. If it pulses the regulator is OK. But yours is most likely bad. (contacts fused)

Here is one on a TC dash check it out!!

(http://i740.photobucket.com/albums/xx46/proguns/001-126.jpg)

There is nothing wrong with my answer.  It tests the circuit and the components.  The Ivr is not tested, because the gauge is not pegged. Clearly i instructed him to test for proper vref at the component.  He would have come down to a bad sender, high resistance, or a bad cluster, if he came down to a bad cluster and wanted to shag around testing the ivr, that would have been up to him at that time, but he'd have followed a diagnostic procedure to that point, and he'd know he was in the right place instead of just taking somebody's word for it and throwing the parts at it he was told to.

I tried swapping clusters before to no avail to this "problem". Now my car probably would have only maybe taken 5 gallons to go that distance, so our problems are related, but may be slightly different. Mine took a long time to come up off of E, yours takes a long time to get full past F. So our problems could actually be opposite. Although I don't have my car anymore, so I can't check.

FOE simmer down!! I just for the life of me cant figure what the hell you were talking about with that trouble shooting procedure ????

It was a way of checking that the signal arrives as it was sent. It would be helpful, I suppose to have the reference values for the component, but my method would have ruled out the circuit, and a new sender is cheap enough to sacrifice to the "known good part" method. A  known good part and a verified circuit, means a problem in the cluster. With a determined  cluster problem, I would have taken him into diag of the cluster, probably pointing to the ivr.  If it doesn't seem make sense, it's because it's incomplete.  He stated that he didn't know if he wanted to go that deep into diag, so I didn't supply any further directions.

It was a way of checking that the signal arrives as it was sent.

Still BAFFLED???

Hi guys---  The dash voltage regulator looks like the way to go because it is cheaper and avoids playing roulette with a used cluster.  I even thought of just installing a temperature gauge to get around this issue.  Please tell me, is this regulator inside the cluster container (that's what the picture suggests)--how do I locate it?  It also seems logical to see if I could repair it first. 

JR

Pull the dash and you will see it. once you remove it a new one is like 20 BUCKS!!! But i do not like the electro mechanical units so i use electronic ones. But you can use a small pair of pliers and a small screwdriver to remove the cover of your regulator and burnish the contacts. This normally repairs them nicely. Then reinstall the cover. Just make sure you pinch the wire that is between the crimp. That is the ground for the regulator. Go slow and be careful and you can repair your VIR. Dont install an aftermarket gauge. They in my view are silly. Unless you do an entire custom dash. Good luck Tom

Also it is a must to repair your dash as the fuel gauge is also involved!!!!

OK Tom---when you say "pull the dash,"  I take it you mean the cluster panel only?

Yes!!!

Thanks Tom---I will look at it this weekend or so.  The link on Ebay was nice, but it appears that those regulators wont fit this TBird---per their check "fit."  First things first--I'll see what condition this voltage regulator is in and see if I can repair it.

listen,,,pls
as you get the connector off the rear of your instrument cluster, locate the gray wire on your connector.
locate the same gray wire down on you ignition switch.
unplug the ignition switch.

use an ohm meter and read from the cluster connector to the ign sw connector.

It is "more likely" the resistance wire is needing attention at the ign switch than the regulator going bad. 
I just now a few days ago had intermittant guages on my sons bird and his little gray wire at the ign switch was highly discolored and when i read its resistance, i personally was reading over a meg..no go.

i cut off about 2'' down at the ign switch and soldered it , remeasured and came up with 8.4ohms.

the little gray wire is a solid strand of "something" metal not really sure what its made of but it doesnt matter, its designed to act as a resistor and reduce the input voltage to the regulator.

if you are taking some time to tinker with the regulator itself, pry up on the flex print connector gently and very precise under the brass looking snaps.  The comment tom made about the IVR ground is good advice, you will see a small copper looking foil where they pinched the cover over it achieving a ground.  this foil transitions to a "hair" sized wire inside the ivr.

I dont know you you feel comfortable opening it up or not, i found it to be easy but its a jewlers screwdriver and tiny needle nose pliar job.

I am just saying to test the wire that makes the voltage input to the IVR first so you dont have to dig in toooooooo  deep.

if your piddling around on this over the weekend, you can buzz me for help at 304 772 3411.

on consideration also that is not mentioned and frankly is very possible.............
It makes no sense why the needle reacts this way when you first start the car,, awsome problem to troubleshoot and i dont think we will see it again EVER.

My second thoughts were that the needle as poped out of one of its holders in the guage.
If you use your thumb and pointer finger and hold a coin standing up, thats how the needle is mounted.  it is not attached though, its axle that it pivits on is about 1/8'' long ,(axil diameter is about 1/64'')and machined to a fine point on each end and these two points sit in a hole that is lets tne neele stand up so to speak.,,verrrrrrrrrrrrry tiny hole.
what i am getting at is that you may have a needle that is cantered or has poped out of one if its holes but is still holding on,, this would cause it to read odly or react to the magnetic lines of flux generated in gauge coil odly.  Either way, first steps in all troubleshooting are visual inspections.. your almost done with this part.
Root cause for a needle poping out could be anythign from a hard bump in the road, cluster was dropped, or someone got so pissed off or agitated that hard force on the dash by hand could cause this...dono.

Foe
other people know stuff to, dont worry about other advise, yours is valid and stable and i personally see this on many of your posts.  this is a very unique problem and im sure it will be one of those things you could caulk up to experince.
it takes YEARS to experince issues like this and thats where you really separate "experince in the job" from "qualified to do the job"

in short, when your actual "fualt" is not on the list of shop manual probable fautls, and you pointed to it first, your finally experinced.

example,,  neck Va naval base-
radar screens were all glowing a slight limish green,, no body could figure out what was causing this.
Tech Reps called in and none of them could either,,except one older guy...who said....

"didnt we just have a hurricain?"  I closed my mouth and opened my ears......

Salc00cher intrusion into the ground ring around the building was hosing up our reference grounds throughout the facility just enough that the only system effected were the array's. (salt being a conductor and all)

i'll likely never see that problem ever again,, but I did once.

things dried up and all went back to normal in a few days slowly.

Hey guys I have now read the posts since last night.  Here's what I got into today...and mind you...I did what I did because it was the most logical and seemingly easy thing to do on this problem (Tom Renzo's comments).  Unfortunately, I had to reassemble the dash stuff to take the Tbird for a spin an hour ago.  I took the cluster off and examined the voltage regulator.  I opened the regulator casing--the contacts did not look bad but I polished them up anyway.  The results are two fold.  The problem appears to be the regulator because both gauges are now pegged out completely!  This occurred less then 3 minutes into the test drive--and I know the engine was still stone cold.  SO.....I know it's the gauges and not the engine--what a relief after some years of trying to get to the bottom of this.  Now I know I can drive the car without concern for the mechanical side of the matter.  So now that I banged up the regulator and presumably sent it to the max output, I presume I will have to get a replacement?  Or should I also be concerned with the wiring as mentioned in posts above?  The regulator has a built in headache--it is mechanically fastened to the plastic circuit board and therefore will have issues with means of replacement.  Pics attached.:bowdown:

I also replaced two bulbs of the nineteen I counted on this cluster.  There were bulbs installed for 1) low fuel 2) washer fluid 3) lamped burned out ,  and even 4) check oil.  We have never seen these in action and I guess that some were probably optional stuff which isnt part of this TBird--but not sure.  ?

PS---I note that it appears this regulator is just snapped onto its electrical partner (the plastic printed circuit board), making it easy to remove?  I also looked this part up and find that it costs about $50 if you wish to buy it from parts stores--and is a special order too!

did you notice the calibration set screw?
if we had an extention cable such that you could plug up the harness and have room to fiddle with it easier out of the dash but still in the car.

if your wires are not broken then it may need fine tuning.

i did not controdict polishing contacts because i have not done it but.... the bi-metal separation is calibrated to complement the spring loading effect of opening and closing during the heat generated while in use. 

take it back out and turn out the adjustment screw , you threw off the calibration by separating the contacts. 
better yet,, just ping someone here for another,, there really isnt a way to get it right without a spare to compare to.  in my book this would be a very tedious task to recalibrate yours.

Jcassity--yeah, my picture clearly shows it- the screw.  I know I'll have to remove the cluster again.  Maybe I can rig up a connection with alligator clips (2 wire and a ground)--at least for the IVR.  Of course, this would have to be done with the cluster electrically attached and the engine off--relying on the Fuel gauge for accuracy (key on).  At least that's all I can think of.  Otherwise, I'll have to spend $50 for something I'm not sure about, and fixing the existing equipment, if possible, is definitely preferred.  I could also check the resistance in wires mentioned.  Thanks--I still have some time this weekend to fool with this.

You have to check the pulses. The regulator pulses a 5V output. So remove the wire from the temp sender place a test light between the wire and ground and look for the pulses. The test light will blink. If it does not blink the regulator is shot. Personally i have never seen a defective wiring issue with a high reading gauge. The regulator controls the voltage because the gauges are not a constant. Another words the fuel gauge can be either full or near empty. That would load down the circuit of the other gauge or gauges and cause false readings. Years ago with 6 Volt systems regulators were not used. I personally never had an issue cleaning the contacts of the regulator. The heater element may be defective. That is why i use the electronic replacements. And yes i remote mount them as well for serviceability!!

testing procedure from the ford service manual

Disconnect wiring harness connector at sending unit. Connect a test lamp or voltmeter between terminal in wiring harness connector and ground.
    With ignition switch in ON position, light should pulse or meter reading should fluctuate.
    If lamp lights but does not pulse, or if meter reading remains steady, check ground to IVR. If ground is satisfactory, IVR is defective.
    If lamp fails to light, or if meter reads 0 volts, check for open circuit across IVR terminals, indicator gauge terminals, or open circuit in wiring harness and printed circuit between components.
    Connect test lamp or voltmeter ground lead to ground terminal in sending unit wiring harness connector. Light should pulse or meter reading should fluctuate as in step 2. If not, locate open in ground circuit. Do not apply battery voltage to system or ground output terminals of IVR, as damage to system components or wiring circuits may result.

Jay the fine tuning can be dun with a lamp in series with the 8.5 OHM wire. If in fact the resistor wire is shot (i have never seen this but anything is possible) A 194 lamp can be used to see if the resistance wire is bad. Put it in series with the IVR and if the gauges even out the resistor is shorted. Once again i have never seen this happen. He has to check for the pulses. If the IVR pulses it is basically good. Actually the voltage does not matter to much just the pulse rate. All dash gauges use the 5V regulator with buttstuffog gauges. And if i am not mistaken all the IVR'S are the same other than MOUNTING. My DODGE had the same exact regulator

One other thing??? Is your alternator putting out to high a voltage??? Have you checked for overcharging??? Just something DUMB i just thought about. Because you now have a regulator that pins the gauges further. So in theory the regulator was working to some capacity. Strange. I have changed several regulators to fix this issue as well as burnished contacts on the units. Well both gauges are effected so the regulator is most likely the ISSUE???

Tom and Jay---I am sitting here trying to digest all this info.  First, if anything, I have had problems in the past with alternators.  The current one---if I don't drive the car for a week, the battery is shy of full crank.  I haven't checked it, but have not had any issues otherwise.  Also, Tom --you gave me a link on regulators (Ebay), but those shown (the cheapest $20) appear not to fit this car per the compatibility check?  The $50 one from the parts stores are simply way overpriced.  Just wonder if the "Compatibility Check" Ebay shows is wrong.  $20 just makes it more feasible to trash the existing and replace it...and where do you find an electronic one?  I re-thought the idea of testing the IVR straight from the battery, but with a resistor wire set into the input voltage, sounds like that is suicidal for the device and/or other components.  Actually, you guys are much more advanced than I and I am faltering on where to go from here.  Spending $50 might sound easy, but that's alot of bread for this deal.

the resistor wire is one continuous wire from the ignition switch up to the cluster connector and its appearance leads you to think its approx 16ga or 18ga wire.
when the insulation is skinned back you find a single approx 24 or so awg wire inside the insulation.  its about 2 or so feet long so its length is probably a factor as well.  It kinda reminds you of a fuse link with one conductor.

I found the tests tom mentions in my shop manuals, they do a good job of explaining it like already written up.

in the spirit of completeness, and since these cars are getting older, maybe you make a good point that a bench test proceedure might be needed, more advanced than the shop manual but simple also.

Quickly thinking through this,, this is what i would do....

-remove cluster to work bench
-find a wall power adaptor that puts out about 5vac like you find on old chordless phones ect and use this for a power source (5vdc may work also, not sure)
-verify adaptor is putting out approx 5vAC, i would let 6vAC go as well because after the circuit is loaded, the voltage should drop.
-cut the end off the adaptor chord that would normally plug into the device it powers
-split the two conductors
-find the positive and negative wires with a meter, (typically positive wire has all the writing on it)
-put a fuse in line with the pos wire going to the pos input side of the ivr
-aligator clip the ground side of the guage to the metal can of the ivr
-aligator clip from the ground side of the guage to one side of a 10ohm resistor
-aligator clip from the other side of the 10ohm resistor to the neg power adaptor wire.
-plug up wall adaptor to ac outlet and your fuel guage should peg

if you use your fuel guage as a point of calibration, the temp guage should follow suit,

I suppose you could do this same test and place your temp sensor in water on a camp stove with a thermometer in the water then calibrate the ivr that way as well.

see quick etch and sketch below..

Currently came back here to recheck all instructions--my intention now is to check the resistance on the gray ignition wire= should be 8.5 ohms?  I also will use a train transformer I have to output a 5vac into the IVR and see what it ouputs on a tester lamp....

sounds good,
the gray wire at the ign switch has 12v.
after the resistance of the wire has its intended effect, you have 5vac present at the input of the ivr.

using your own power source you will make both the fuel guage move.


you should be able to simply ground your temp guage wire out and it will peg out with a slow but smooth needle movement.  i would throw the 10ohm resistor in line with the ground leg as well for some degree of protection.

good luck, you came in leading us on to thinking you werent really able to do all the things you doing now but i am impressed.  good work and hope we can help nail this issue,, as old as it is it would be nice to be done with it.
like tom said, if you watch real close you will see the needle sorta twitch,,thats the AC going though stuff.

This likely might be one of my last necessary posts on this thread--because the problem appears solved!!! Earlier today, I had the cluster back out. I rotated the calibration screw back out about 1 1/2 complete turns--purely a guess. I also located the grey/yellow striped wire in the left connector for the cluster. Note --all the wires in the loom were striped except one black one which was also located in slot 12. There are actually 2 grey/yellow wires and I got a reading on the one located in position 12 (the smaller of the two). I connected an ohm meter to it and its terminus at the ignition and got nearly 9 ohms. I put the cluster back in and drove the car about 12+ miles, 8 of that on the interstate. Today is 90+ F here; sun out and high humidity. The info was: The temp gauge remained cold for about 5 minutes from the house and then slowly climbed to more than 1/3 of the operating range--about what it has always done long in the past. I topped the gas tank (1/2 gal) just to see where I could get the fuel needle to go. It now looks more realistic at the top of the pin points indicating full. This new place for it is less than it used to show (in the life of the car). After the interstate, I stopped in a lot and shut the engine off. 5 minutes later I restarted and watched the temp needle actually start at midpoint and then back down as I might expect it to since the fan would be running etc. It all seemed very normal to me. Above --I mentioned a black wire in the loom also tucked into slot 12. When I was reinstalling the cluster, the black wire revealed itself at a factory taping of the wires--the old tape fell off. The wire was cut off. At first I thought I had made a bad error in severing a wire while positioning the cluster. Not so----there was no further piece of wire found and it appears that the factory simply installed it that way---perhaps an unused option--who knows. It did confuse my testing to see that black wire in there. The pictures I include here show the car on the interstate, well into the trip (already gassed up again). #2 later in the garage at home after pulling in (engine off).

I thank you so much guys on this thread with your help!!!!!!!--without it I would not have succeded in making this repair--not to mention that I didnt spend a cent for the IVR repair!! Tom Renzo pretty much had this one pegged from his first comment--BRAVO TO YOU! What would cause the IVR to drift off accuracy-- just age?--meaning that it needs to recalibrated or something else changed the envelope of temp operation? I chose to BACK OUT the screw because it was obvious with the heater wire, the points are meant to float and open. Telling me perhaps they were not doing it because of too much forward tension on the lower arm. I can post more pictures --maybe for someone else's reference on this subject. This was the most puzzling and annoying issue I ever had with a vehicle. Our T-bird has always been well cared for and had little problems--so when this headache started about 6 years ago, I was determined to get to the bottom of it. Unfortunately, a bunch of engine components including a fan clutch and water pump were part of the list. I'm happy anyway as they would likely needed to be replaced at some point.

JR

Good job and as i stated i have replaced many of those units with electronic ones. They go bad and cause all the gauges to read very high!!

Yeah I just saw your post jcassity---again much gratitude to all on this as every post including the wiring diagram was essential to my understanding of this matter.  Fortunately, I have previously learned how to read wiring schematics and that was a tremendous help here in understanding this temp operation.  These pics show the gauges before the work--with the temp gauge short of H--and would go closely there.  Also the fuel gauge minus 10 gallons.  The IVR shown.

Thanks so much TOM!!!!

good calibration guess, thought that might cure it if the gray wire had good resitivity.  9ohms is a good reading in my opinion.
time to put this dog to rest.. *SOLVED*

Just a FYI for anyone else--I found this on a Google search--a Mustang forum.  This is a do it yourself solid state IVR but the one shown I believe is meant for a '60s Mustang.  I am sure an electronics tech here could reconfigure.  The 3rd picture leaves the unit to be figured for hook up.  The parts cost less than $10.  Since our units have snap connection to the cluster--I suspect someone could come up with the answer on both counts:  Correct calculation and parts and 2) hook up.

And maybe finally---an EBAY seller in Florida selling the IVR fitting the '88 T-BIRD.    Note my pics on the DIY IVR above were placed out of sinc.

to do this, a person would have to ommit the resistance wire from the ignition switch so 12v arrives at the coverted ivr.

i have a forum in electrical tech called the mysterious instrument cluster problem something of that nature any way seeing that you have taken to fixing instrument clusters, some aid would be much appreciated if you can check it out thanks