Skip to main content ↑ ↓
Topic: Sentry system sensing a headlight out (Read 4278 times) previous topic - next topic

Sentry system sensing a headlight out

Need some help please. I installed the relays tonight for the headlights. I wish to run the fogs as well as the headlights and don't want to take any chances. Everything works so far as required. Problem I have is the vehicle sentry system now has a light indicating a headlamp is out. The kit that I bought does not use the right side headlight plug. It is all powered from the left hand plug. I guess I'm asking if anyone else has had this issue and more importantly, how do I fool the sentry system into thinking the headlight is working? Can I install a jumper line on the original headlight harness. There are only three pr0ngs. What ones would I use the jumper wire for and is it safe to do that?  Any help would be appreciated please.

Go Fast the first time.  The tickets the same.
86 Thunderbird 5.0.  All original good weather driver. Tbird Reg #53035
86 Thunderbird TC.  All original good weather driver.  Tbird Reg # 58555
87 Thunderbird TC.  All original good weather daily driver.  Tbird Reg # 64647

Sentry system sensing a headlight out

Reply #1 –
How big is the left hand plug, sounds like you need to add another wire to me.
Quote from: jcassity
I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
Hooligans! 
1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
1986 cougar.
lilsammywasapunkrocker@yahoo.com

Sentry system sensing a headlight out

Reply #2 –
Well I can tell you John is not because of the one plug not being used. I went the route of modifying my factory wires to accomplish the same thing as the kit you installed, and I have the same result. I haven't had the time to figure out a remedy myself yet.

Sentry system sensing a headlight out

Reply #3 –
John,  I believe the sentry reads amp draw for a "headlight out" scenario. With the relay mod done you are pulling way less amps,  thus the safer design.  The sentry is set up to look for a low amp draw.  I've done the mod on a few tc's I've owned and never was able to figure  out how to get around the low beam light issue. Maybe j cassity  will chime in, he's an electrical wizard
41 Dodge Luxury Liner Sedan
78 F-100 2wd flareside
84Turbo Coupe
84 Thunderbird Élan
85 Thunderbird 3.8
88 Turbo Coupe
88 Mustang GT
90 Stang LX 5.0 5spd
93 F-150 4x4 ext cab
96 Mustang GT
98 Mustang GT
99 SVT Cobra
06 Fusion SEL
14 Fusion Sport
 

Sentry system sensing a headlight out

Reply #4 –
Quote from: Haystack;432846
How big is the left hand plug, sounds like you need to add another wire to me.

The left hand plug is the original headlight plug directly off the headlight.  The relay system I purchased was pre made and uses just one of the original headlight plugs to get the power from the headlight switch.  Then there are two new plugs that go to the headlights from the relays.  It's all pre made, grounds were attached and power added directly to the battery as required.  There is just nothing to attach to the original right hand headlight plug.  No missing wires etc.  Hope this helps to clear up the matter.  I did not make my own relay system this time.  Last time I did, I wasn't very successful the first time out.  Took a second attempt to get it to work right.    Decided for the money and time involved it would be much easier to plug and play so to speak.

Go Fast the first time.  The tickets the same.
86 Thunderbird 5.0.  All original good weather driver. Tbird Reg #53035
86 Thunderbird TC.  All original good weather driver.  Tbird Reg # 58555
87 Thunderbird TC.  All original good weather daily driver.  Tbird Reg # 64647

Sentry system sensing a headlight out

Reply #5 –
Quote from: Tbird-fanatic;432857
Well I can tell you John is not because of the one plug not being used. I went the route of modifying my factory wires to accomplish the same thing as the kit you installed, and I have the same result. I haven't had the time to figure out a remedy myself yet.

Tony, I'm glad to hear I'm not the only one with this problem.

Go Fast the first time.  The tickets the same.
86 Thunderbird 5.0.  All original good weather driver. Tbird Reg #53035
86 Thunderbird TC.  All original good weather driver.  Tbird Reg # 58555
87 Thunderbird TC.  All original good weather daily driver.  Tbird Reg # 64647

Sentry system sensing a headlight out

Reply #6 –
Im thinking about looking at the wiring diagrams  and figuring out which wire it is to the Sentry and just snipping it and taping it off. Since one the relay mod is done it really would never be able to tell you without some massive rewire to hook it back to the headlamps. Though Im still playing with the idea of eliminating the System sentry for a place for real gauges!! When I finally get to the point I want to be, on top of my boost and pyro gauge, I want to have real gauges for oil pressure, coolant temp, and at least a Wideband O2.

Sentry system sensing a headlight out

Reply #7 –
Looking at the diagram I dont think snipping the wire will work, unless the light is lit from the power going to the headlamps. Theres actually 2 wires that go to the sentry from the headlamps, one on either side of a resistance wire. which would mean anything put in to simulate the amp draw from the lamps would just create the draw agian defeating the purpose. I should see if its possible to just disassemble the sentry and remove the bulb that lights up.

Sentry system sensing a headlight out

Reply #8 –
Probable more than one way to skin the cat here.
If just want the light to go out, you can cut the wire from the module that provides ground for the "low beam out" light.
If you want the warning light to work, that's more complicated.

The R/LG wire at connector C240 is the wire to cut.
The module is under the right side of the dash. Pull the glove box. Pull the two mounting screws and move it to where you can get to it.

Giving you two diagrams of how it may be mounted.

Sentry system sensing a headlight out

Reply #9 –
One more

Sentry system sensing a headlight out

Reply #10 –
jandmmustangs is correct. The Lamp Out Module is designed to detect a drop in current draw to the headlights.
It does this by monitoring the voltage drop across the resistor wire.
0.5 volts = lights are good.  0.25 volts = one light is out.  0.0 volts = both lights are out.

If someone will take some voltage measurements, maybe you will get lucky and find a 0.5 voltage drop.
With the lights on:
Measure from the battery + to the lights side of the fuse.
Measure from battery + to the lights side of the relay contacts.
If you find a voltage drop in the neighborhood of ½ volt, a fix could be as simple as running a couple of sense wires back to the module.

Sentry system sensing a headlight out

Reply #11 –
John if you don't mind that light not being functional, you can just pull the bulb. I just looked at my extra one and they just twist out just like cluster bulbs. I think if I keep it that's what I'll do.

Sentry system sensing a headlight out

Reply #12 –
Quote from: softtouch;432912
jandmmustangs is correct. The Lamp Out Module is designed to detect a drop in current draw to the headlights.
It does this by monitoring the voltage drop across the resistor wire.
0.5 volts = lights are good.  0.25 volts = one light is out.  0.0 volts = both lights are out.

If someone will take some voltage measurements, maybe you will get lucky and find a 0.5 voltage drop.
With the lights on:
Measure from the battery + to the lights side of the fuse.
Measure from battery + to the lights side of the relay contacts.
If you find a voltage drop in the neighborhood of ½ volt, a fix could be as simple as running a couple of sense wires back to the module.

So if I understand this right, the relays won't allow the proper voltage either way.  So without taking any readings it could actually be sensing both headlights out correct?  Why did Ford have to make this system the way that they did.    Bad switches that overheat, and the like.    They are great cars so I guess I'll have to adjust and live with it.    I'm not sure I want to start cutting wires, the car has not been hacked up in the wiring yet and I'd prefer to keep it that way.  Maybe running an extra wire would be easy enough.  On the other hand, it might be just as easy to leave it and live with it.  It's just a light.    My air bag light has been on in my truck for 5 years.  Bad sensor.   

Thanks for the info.  Doesn't sound like anyone has actually made this work though.

Go Fast the first time.  The tickets the same.
86 Thunderbird 5.0.  All original good weather driver. Tbird Reg #53035
86 Thunderbird TC.  All original good weather driver.  Tbird Reg # 58555
87 Thunderbird TC.  All original good weather daily driver.  Tbird Reg # 64647

Sentry system sensing a headlight out

Reply #13 –
Quote from: Tbird-fanatic;432927
John if you don't mind that light not being functional, you can just pull the bulb. I just looked at my extra one and they just twist out just like cluster bulbs. I think if I keep it that's what I'll do.

I should have read all the postings first.  This sounds like an easier fix.

Go Fast the first time.  The tickets the same.
86 Thunderbird 5.0.  All original good weather driver. Tbird Reg #53035
86 Thunderbird TC.  All original good weather driver.  Tbird Reg # 58555
87 Thunderbird TC.  All original good weather daily driver.  Tbird Reg # 64647

Sentry system sensing a headlight out

Reply #14 –
I would have come up with it a bit sooner if the car and parts werent out at my FIL's place!!! LOL