On my 86 cougar, only the high fan position worked. One day while i was driving, the fan shut off. How does the fan controller work? Im guessing it has a wipe on a resistive wire, similar to the dimmer switch. This would explain why only high worked before.
Fuse is good, have power to horn ect as well. Am i looking at a new heater control? Is there a wire i can temporarly jump or wire in a switch to get me by a month or two till it warms up a bit?
Only the high position working is the blower motor resistor. I'd put money on the blower motor itself going out before the controller.
I have a NOS switch for an 86 cougar that I will never use, PM me if you want it.
The blower will only work on high if the "thermal limiter" is blown. The limiter is part of the blower resistor unit mounted on the air box.
Fuse 9 is only used by the blower, nothing else.
The resistors are not used in the high speed position. The speed selector switch could be bad. You could try grounding the Orange/Black wire at the speed switch.
More diagrams in a few.
I also have the part listed above, also NOS.
It may be easier to unplug the cable from the blower resister on the air box.
You should have voltage on the orange/black wire with the key on and the function switch in any position except OFF.
Grounding the orange/black wire should make the blower run.
Sweet. Thanks guys. Hopefully its just the resistorso I can jump it. If its not, not worth the trouble to have a working heater right now.
Not really
Quietleaf and a few of us did some observations and rewiring to the manual controls of the heater assembly
Quietleaf found that the controls themselves on the connector would get very burnt and possibly catch on fire
Hopefully it is an open circuit down at the controls otherwise the blower motor it's self or the resistor assembly has burnt open
Good luck haystack
By the way I don't have one single set of manual heater controls but a few other guys have already replied
Wish I could pay back the favor
By the way a 26 or 28 gauge short chunk of wire soldered in place of the thermal limiter could stand as a decent repair
Or you can just go to RadioShack or some other electronic supply house
I have a couple of threads about this in my DIY link below
Just to clarify a little, you have two problems.
1. Only runs on Hi, is the thermal limiter on the blower resistor unit blown.
2. Not running on Hi. This has nothing to do with the resistor. You can remove the resistor unit and it should still run on Hi.
It is probably the motor, but you can make some checks to make sure.
If grounding the O/BK wire in the plug to the resister makes it run, the blower speed switch is bad.
You can check for voltage coming into the motor at C275 the DB/LG wire.
I agree on the resistor, either the thermal limiter is blown or the or the medium high element is open. In either case, the part is stupid cheap, so don't cobble and hack your way around it, it isn't worth a vehicle fire. Second, it has to be mentioned that for the thermal limiter to be open, the blower would have had to be overdrawing the circuit. Since you ignored it, and kept using it exclusively on high, you now probably have a blower switch burnt from being overdrawn for extended lengths of time. You can replace those 2 easily, but you still have to address the root cause, which is most likely a bad blower motor. This is what would be referred to as the causal part, and parts went down one by one due to neglect and the in-range failure of the blower. Had you replaced the resistor right away, you would most likely have had the thermal limiter open on the replacement almost right away. No easy way to say it, but you're pulling the dash in any scenario that includes getting system function back.
if you find your blower motor did survive,, and its the controls for either or both speed and selector.. here is a diagram to solve this for ever.
just repin wires in the areas shown, add relays and protection.
Hmm. Never seen that before. Is there a thread on it? Would be interesting to read up on.
If the blower motor itself has given up the ghost, bring the old one with you when you go to grab a new one. The parts # listed for these was NOT what was in the case; at least not in mine which has the ETC. I don't envision there being an actual different blower motor for ETC cars, but hey, it's possible.
Anyway, the one that many parts stores has listed would not even come close to fitting. IIRC The correct one had a Ford part # that started with D8.....
I disagree with the theory that an over current situation blows the thermal limiter.
The reason the blower resisters are mounted in the air box, is because they get very hot.
The reason they use the open coil type resisters is so the air moving through the box can carry the heat away.
Low or no air flow will allow the heat to buildup around the resister and blow the thermal limiter.
An over current situation will blow fuse 9.
An in-range failure is defined as any failure which does not overcome it's safeties or exceed fault tolerances by a sufficient margin to set an alert. The thermal limiter is a slow reacting fuse meant to open based on the temperature of the conductor within (not without as blower airflow addresses this). The coils are cooled by blower discharge, but the thermal limiter is almost completely unaffected by air-cooling. The conductor within varies in temperature based on the amount of current being drawn though it. A thermal limiter will be labeled with a temperature and an amperage, that amperage will typically be 75% of the fuse at the head of the circuit, in this case 30A. Go ahead an put an ammeter on a blower motor, run it at any speed you want because you won't be anywhere near the fused current, not at full-speed, half-speed, or even during initial blower kick. If you begin drawing too much current, as you would on an older car when the brushes wear out, or the bushings begin to bind or the field coils begin to drag, you'll do so for long lengths of time because unless it's noisy, you won't have any idea something is wrong. This won't bother the fuse because it is set to open purely based on current. The thermal limiter on the other hand is a fuse that opens based on heat created as current is drawn through it. The thermal limiter is expected to open between 20 and 25 amps on this resistor block, when that current is exceeded for an amount of time sufficient to cause a given amount of heat. The 30A fuse will blow quickly to protect the wiring, usually from a short. The thermal limiter opens to protect from component damage (like a melted blower switch) related to an in-range failure (although vehicles like E-vans and older Focus will melt them down anyway). That blower is junk, and until it's replaced, he'll be feeding it resistors one after another. This is what I do for a living, and I've been at it as a specialist for 15 years.
yeah, wanted to find it, seems i didnt save it. it was sometime in line of aug 2012 when someone,, i think it may have been quietleaf who posted pics of the connector being burned up ,, you know where it plugs into the manual controls.
oh, wait,, ok,,
yeah there are three threads on it in my diy link ,,,, but the thread that shows the burnt connector i could not find,,,, that diagram i posted is the end result of such an investigation... look at the date / rev number on the top.
it was tricky but ,,, speakign to haystack ,, sure hope he gets his heat back!!!!!!!
partially agree,, but,,,,,, i do side with softtouch because of two words
"use" & "application"
In this case, he proves his point or should i say all of have or will one day ,,, when the blower motor barely turns at all on low speed because of garbage attached to the squirril cage.. the wire wound resistors get hotter than normal... and well.. its all down hill from there.
in this case again,, its the application. the application is a design the depends on a certain cfm of air movement to keep up with an engineered ambient temperature within the box.
welp,, umm,, hes been doing it so long some of the stuff hes done comes on the history channel :)
for instance,, softtouch can "look" at a punch card and tell you what it says.
Running on any of the resitively controlled speeds would increase load, technically it should use the least power on full. I actually have quite a bit of experiances with electrical curcuits, amp loads, and electronics in general.
I havent actually looked into it yet, but ill get around to it tomorrow.
I'm telling you, that blower is pulling too hard. I've seen it, I've had it, and I've dealt with it more times in 15 years than I can count on one hand. I'm not telling you about theories and concepts, I'm telling you what I've seen and done.
no doubt,, either way sumthins broke shiznit.. lol.
Yeah, I agree. But that doesnt mean the motor broke. I feel that.generally most of the electrical in these cars is way under built.
The motor probably DOESN'T seem broke, but it's drawing too much current, and can you say for sure it's spinning as fast as a good blower motor? It probably isn't, but these changes don't happen abruptly. If you put a frog in a pot of hot water he jumps out, but if you put it in cold water and raise the temp, he doesn't notice he's being cooked to death.
Yes, but this isnt a frog. Its a 27 year old $500 car. And it IS fused. I am very familiar with electric motors, wiring and even efficiencies of old worn out brushed motors. If it last another week or two and i dont have to pull the dash ill be happy. If it blows the 30 amp fuse, then i know i have a problem.
REALLY so explain to me why High speed in just about every blower system on the planet has a dedicated power feed that does not run through the switch????????????????????????????????? BECAUSE ON HIGH SPEED IT DRAWS THE MOST CURRENT. LOOK AT THE PRINT STACKS! HELLO!!!!!!!!!!!
The thermal limiter is OPEN and that is why it only runs on high.( NO GROUND THROUGH THE LIMITER MOTOR DOES NOT RUN ON REDUCED SPEEDS) Follow the ground path. You can really get fancy and cut out the thermal limiter and install a fuse or jump it ouit. Normally if the blower motor starts to draw more current (AGE BUILD UP OF shiznit ON THE SQUIRREL CAGE THE LIMITER CAN BLOW I GUESS But ford has had issues with those limiters as well as GM . They just go open plain and simple. This can be easily checked with an AMMETER FOR CURRENT DRAW IF YOU LIKE !! Check current draw on the motor with an AMMETER running the motor at high speed. Should be under 20A or so!! Remember the motor draws maximum current at full speed!!! Replace the relay assembly and call it a DAY!!! Actually i think some of those are DIODES. Been a while!! NOT 100% I know some on chevys are!!
no relays in this circuit major tom :)
and he said on the first go at this thread that the motor does not work at all,, not even high. double check post 1
here are those links to blower motor stuff,, still cant find that one thread where someone posted a pic of a burned elec connector of the manual heater slector switch.
Blower motor relay modification to take heat off the selector switch and the speed control switch.
*be sure to read post 24 about our factory switches ~thanks tom renzon~!!
http://www.foxtbirdcougarforums.com/showthread.php?17041-fan-blower-location
Blower motor troubleshooting Blower has HIGH speed only and wiring diagram
http://www.foxtbirdcougarforums.com/showthread.php?19544-88-tc-fan-control-works-on-high-only&p=220320#post220320
Blower motor troubleshooting and wiring diagram
http://www.foxtbirdcougarforums.com/showthread.php?17041-fan-blower-location
Jay 29 Posts on a blower motor that only had high speed and now does not run. If he can not figure this out well what can i say. You and others have covered this many times in excess. First off i was posting on the HIGH ONLY portion of the issue and second hot feeding the motor would have cleared this up in two seconds, hay here is a wake up call his relay went out first then a motor or wiring issue captain!!! But when someone comes on and spouts of as being an expert and posts that a motor that runs at a slower speed draws more current how do you answer such NONSENSE, Thanks JAY Have a good day!!
Note some of the replacement speed relays or variable resistors were coming through with limiters on the entire ground circuit. Not sure if it was Ford or GM. Just a talking point
What do you think of my position that the blower is responsible for the open thermal limiter, now? I also told him to look at the blower switch for signs of melting.
My entire thought chain:
Bad blower -> high current -> more heat in circuit -> open thermal limiter -> only functions on high -> draws most possible current -> overheated blower switch -> 1. possible blower switch failure, 2. possible blower motor dead
Foe if by now you actually think you are going to get some common sense from the original poster you are NUTS. But here goes on your theory which i believe is correct by the way. . Those Thermal limiters showed up @ or around the vintage years we are dealing with. Now many companies use them and some were marginal at best. So i have replaced many over the years that did not require a motor change out. As the matter of fact MICE NESTS plague us up north. I have removed many a MOUSE from a blower motor!!! Many did require a change out. As debree and bearing drag increase current rises and loads down the circuits more. Naturally over time it loads down the connectors switches and thermal protectors. This is still going on today!!! I keep several connector UP DATE kits in the shop for GM FORD AND CHRYSLER. Yes what you posted is correct and factual as far as his issue is concerned. But getting that in to his head is another lost cause, Thanks
FOE i need to ask you a question on a cranking issue on a 4.0 Explorer if i may. I might have to move this to Genrtal but here goes. I have a customer with a 1999 4.0 explorer that sometimes when cranking it seems like the timong advances and the engine lugs before firing. Another words it cranks fine to the point of the second it ants to stare if seems like the timimg is advanced 30* and it slows down. It always starts but it is do dam intermittent i can not put my finger on it. It almost sounds likie a cross fire before starting but the dam thing runs and drives perfectly. Any ideas?? Thanks
That's a SOHC 4.0L?
Maybe we do this via PM.
Sohc is correct
Chain noise on cold start?
Not really it had the recall dun by the dealer
Foe, not trying to step on your dick here, but I'm looking at a current draw chart in the 84 shop manual.
Tell me what you think.
The motor current draw Hi= 7.0 amps Med= 3.5 amps Lo= 2.0 amps.
The Med resistor cuts the current draw to half the Hi current.
Lets say for discussion purposes the motor with a locked armature drops to zero resistance.
The current draw on Med would go to 7.0 amps.
I don't have one of these resistor assemblies to look at, but in places I have looked that sell thermal limiters they typically have a current rating of 15 amps.
If the motor is struggling to run on Hi it could stall on the lower speed settings.
The resistor now has twice the normal current and no cooling air flow.
The source of the heat to melt the "wax" to allow the spring loaded contacts in the limiter to pop open is the resistor overheating.
According to the 1986 spefications book, current draw on high SHOULD be 11-13 amps, and I pulled the resistor from my old heater box (because I almost never throw things out) and the thermal limiter is labeled 15A. We should consider that if you placed an ammeter across the blower circuit from the fuse to the ground, current would register nearly the same whichever speed you are set at, the resistor limits the current through the blower by consuming current itself (this is why we have to cool the resistor). We can assume then that under the best of conditions we're within 2 to 3 amps of the thermal limiter's capacity at any time when the blower is being operated. Is it really that hard to imagine a 28 year old blower drawing 2 to 5 more amps? And remember that with voltages fairly constant, the draw for each resistor stage is static, so the resistor can never draw more current that it was designed to, but the blower can. The blower can draw as much current as is available to it if it needs it to spin (assuming, of course, that it CAN spin). And a thermal fuse as used in a blower resistor is not a wax type thermal fuse. It's more like two electrical terminals connected by a length of solder (although it isn't solder). This is different from an old AC clutch thermal limiter or one like you would find in a dryer.
I am guessing you mean volt meter. If you hook up your ammeter like that, you will blow the fuse in the meter. The current through the fuse and everything else in the circuit will be the same as the current through the motor.
It reduces the amount of current flowing in the entire circuit from the fuse to ground.
When in Hi, no current is flowing through the thermal limiter. Using the ratio I posted, at Medium speed you will have half the 11-13 amps flowing through the thermal limiter. At Lo speed you will have even less.
The resistor is in series with the motor. In Med or Lo all the motor current has to come through the resistor. The resistance of the circuit is the resistance of the motor added to the resistance of the resistor.
In Med or Lo the current draw is limited by the resistor in series with the motor.
How is this any different than a fuse?
With the speed switch in Medium, if you shorted out the motor the current draw through the thermal limiter would be 11-13 amps limited by the resistor.
To sum up, you are never going to draw more than 11-13 amps through the thermal limiter, no matter what the motor does.
You're nit-picking me to death here and completely missing the point. And the point is that Stacks' blower is junk. The resistor is open, because the blower is junk, and if the blower turns out to not be completely dead, his blower switch will probably be melted down. In all scenarios, he needs a blower and a resistor, possibly a switch, and no matter what, he's got to pull the dash to change the blower. You can argue semantics and fine details with me until rapture, but none of it changes these facts.
You are absolutely right about what it will take to fix the problem.
I just thought you were a details guy who would appreciate knowing how and why the limiter works.
fast backwards a little bit.
post 1 clearly stated he "use" to have high only but now nothing.
so Major tom,, there is no relay in this OEM circuit
Can you please ignore the fact that people ask the same questions over and over again,, just enjoy answering because its why this board is here.
Foe,, your agreeing with us on everything except how you call things or what they are named,, either way something broke shiznit from the the source on down stream.
the whole circuit is kaput.
so,,, till haystack comes back and tells us what does work,, its all speculation.
JAY 40 posts on a blower circuit that is the bottom line of simplicity is MIND BOGGLING. But it did do one thing!!! At least it shows Stacks that when a motor slows down it draws less current. As far as the limiter goes years back they did not even EXIST!!!! Just speed resistors. Most high speed fan circuits are 30-40 A and the lower speed are normally 20-30A. JAY I NEVER SAID A RELAY WAS IN THE CIRCUIT. Clearly the print does not show it. I can read prints very well JAY. But this circuit is a ground variable setup instead of a battery one. Not that it makes a difference it does not. The motor sees less voltage and current to slow it down either way.
Just for the record here the thermal limiter in this circuit has nothing to do with MOTOR SPEED. It is exactly what it is called a ONE TIME FUSE OR THERMAL LIMITER. It has a fancy name but it is basically a ONE TIME FUSE GUYS NOTHING MORE!!!!!
To sum up, you are never going to draw more than 11-13 amps through the thermal limiter, no matter what the motor does.
WRONG!!!!
If in fact the motor armature or cage is locked the current would go through the moon on either LOW or Medium setting and until it reached the capacity of the 30 amp fuse or the capacity of the limiter whatever that is. and at that time the 30A fuse or the limiter will blow rather nicely. Personally i do not know which one will POP FIRST as i do not know the current capacity of the limiter. Naturally on high the 30A fuse will be the natural choice of sacrifice!! If memory serves me those thermal limiters are there to keep the resistors from overheating and nothing else That is why they are called thermal limiters.
At any rate I'm tire of getting emails about this thread, unsubscribing.
I know my communication skills suck. But let me try one more time.
1. The circuit with the blower switch on High:
Fuse--function swt.--motor--blower swt.--ground.
Current draw =12 amps with a good motor.
2. The circuit with the blower switch on Medium:
Fuse--function swt.--motor-- blower swt.--resistor--thermal limiter--ground.
Current draw= 6 amps with a good motor.
Since putting the resistor in the circuit makes the current drop by half, means the total circuit resistance (motor+resistor) doubled.
This means the medium speed resistor has the same resistance as a good motor.
This means with the blower switch in medium, the maximum current draw you can have with a bad motor is 12 amps.
12 amps is less than the 15 amp max current rating of the thermal limiter.
With the extra current through the resistor and less air flow the resister overheats and trips the thermal limiter.
Thermal limiter, thermal interrupter, thermal fuse all different names for the same thing. They come in different sizes and shapes and
different designs. Their function is to break the circuit if the ambient temperature of the environment they are in exceeds their temp rating.
Haventt gotten to this yet. I'm not going to argue the blower isn't junk, as well as being extremely limited in function and design. now that we are playing the experience game...
I have close to 40 flyable model airplanes all running small electric motors. I have one setup that pulls 49 amps and over 500 watts at 12v's. This produces over 7lbs of thrust at over 80mph. I have well over 1500 hours this past year alones flying these small electric motors, and easily half that playing with amp loads, motor combinations and other variables. even though its a hobby, I am very knowledgeable with these types of things. I pull a watt meter out of my pocket 3-5 times a week.
If I go through the effort of pulling the motor out, a stock setup isn't going back in.you'd have to go to radio shack to come up with a worse system. I just wanted to temporarily bypass a bad switch to see if I could get by a couple weeks. not argue if something was broken.
This really hasn't been a priority though, since it has been tshirt weather and on the freeway, it easily pushes enough air through the vents to defrost the windows.
Thanks for all the help and schematics.