Lamp Failure Module cooking

[d3fc0n]

Greets all --

This is my first post, be kind.

I have a 1987 Toyota Supra, 7MGE non turbo, stock. My pops said my tail lights were out so I went to Wal-mart and purchased the new bulbs. They were obviously bad, they were blackened. The tail light assembly is original and is very crumbly from age. The bulbs were corroded within their sockets. I cleaned the sockets with WD40 and some sotch brite to remove the corrosion and inserted the new blubs back into their respective sockets.

All goes well for about three minutes...

After that, I noticed a very bad smell coming from the driver side rear bulb compartment. Noticing the Lamp Failure Module was very hot, I removed it and opened it up. It's a yellow box, about 3"x3"x1" or so, for those of you who are interested. Upon opening the sensor, one of the wires cooked and the the PCB it was soldered to was damaged by high heat.

I then ordered a new $180 Lamp Failure Module from Toyota, hooked it up, and it, too, unfortunately, cooked in the same place.

Obviously I have some kind of wiring short. The fuse under the driver side kick panel for the 'Tail' light is not blowing, it's a 15A fuse. My question is, where should I look for the short? Could the Lamp Assembly be causing it? Would it be safe to bypass the Module with some of the Mods I've seen floating around on the Internet? I'm open to suggestions.

Thank you for your time.

___
Larry

 

[s383mmber1]

for 180 bucks you could have bought 89+ tail lights

 

[d3fc0n]

for 180 bucks you could have bought 89+ tail lights

Haha, yeah, no $hit.

 

[jetjock]

Now now, he asked you guys to be kind. But yikes, no kidding. I've seen Lamp Modules go for $5 on ebay.

What bulbs did you put in? Remove them or disconnect the wiring from the tail lights (including the CHSL if it's incandescent) then try it. Or ohm the light assemblies out to see where the problems is. You don't have a ground fault or short, if you did the fuse would blow. You have a low resistance path causing excessive current (yeah I know, the same could be said about a short but that's not what I mean). Check for carbon or corrosion byproducts in the sockets, boards, and wiring. You can bypass the LM if you want but find the problem first.

Btw, WD 40 is the wrong stuff to use for what you used it for. In fact it's not much good for anything but removing stickers.

 

[jd20phill]

and cleaning your hands

 

[d3fc0n]

Now now, he asked you guys to be kind. But yikes, no kidding. I've seen Lamp Modules go for $5 on ebay.

What bulbs did you put in? Remove them or disconnect the wiring from the tail lights (including the CHSL if it's incandescent) then try it. Or ohm the light assemblies out to see where the problems is. You don't have a ground fault or short, if you did the fuse would blow. You have a low resistance path causing excessive current. Check for carbon or corrosion byproducts in the sockets, boards, and wiring. You can bypass the LM if you want but find the problem first.

Btw, WD 40 is the wrong stuff to use for what you used it for. In fact it's not much good for anything but removing stickers.

Jet--

What would I be looing for when I ohm out the pigtails? Could you give me a little bit more information? I'll let you know if I find any corrosion within the sockets and hopefully with your help this irritating problem will be done.

Thank you very much for your helpful comments.

___
Larry

 

[jetjock]

Jet--

What would I be looing for when I ohm out the pigtails? Could you give me a little bit more information? I'll let you know if I find any corrosion within the sockets and hopefully with your help this irritating problem will be done.

Thank you very much for your helpful comments.

___
Larry

Remove the bulbs and measure each pigtail or each socket. You should get infinity (open circuit) in all cases. If you measure anything less than infinity you need to track it down. The bulbs will be only a few ohms when installed. Measure one not installed and compare it to what you get on the pigtail after installing it. Understand I'm talking about the wiring on the tail lights, not the wiring in the car. I'm assuming you don't have this problem when the bulbs are removed or the wiring is not hooked up to the tail lights. If you do the problem is upstream of the tail lights. Don't forget the light on the spoiler.

You could also hook up your tail lights to a battey or power supply if you have access to one. Use a 5 amp fuse in the line and measure the current with your meter. Trust me, when it comes to cars a DMM and the knowledge to use it is your friend

Btw, there are at least two LFMs on ebay as I write this at $1.

 

[mattsplat72]

i had the same problem on my 92 turns out it was water leaking past the hatch seal and frying the wires inside the box so i just took to ziplock sandwich bags and sealed the relay in them and havent had any problems just be gald you got it cheap mine cost 238 at the dealer

 

[d3fc0n]

An update from yours truley:

As it turns out, the entire problem stemmed from a) It being 40F outside, and b) 40mph wind gusts.. do NOT attempt to work on your vehicle in horrible weather conditions -- it's just not worth it.

Basically, it was an ID 10 T error on my part. I had a one prong bulb in where a 2 prong bulb was supposed to be shorting the two prongs that eventually caused the demise of the LFM. Replaced the LFM from a warranty(!) part from the dealer and the correct bulb. Now I'm back in the game.

Many thanks to all of you who gave me very useful information. In the end tho, it ended up being good ol detective work that solved the problem. Gotta hand it to my pops, without him, who knows where I'd be with this problem now.

___
d3fc0n

 

[lifesnotfair]

I got my module today, I tested it for 10 seconds, it worked when someone hit the brakes. GOOD.

NOW, the weird thing is, this module is different from mine. Mine was more yellow, this was more like... hrm... sand color... a much lighter yellow, not even yellow possibly. Also, the connector on this new one I got, is like on the center-upper part. On my car's yellow module, the connector is on the LEFT-upper part... I will replace my car's module today, hoping it keeps working for good. After I do that, I will also open my yellow box once it's out, and see if any resistance or anything blew, to see if it's repairable.

Also, I switched to JDM tail lights. Do I need a different module? My car is 88 so probably the modules changed too in 89? Lol, I have no idea.

Will let ya guys know later. Will be a pleasure to FINALLY drive without the bloody "tail light failure" light lit in the dashboard... it'll be so great..

 

[lifesnotfair]

By the way, this module costed 8 bux plus 5 shipping. Truly expensive stuff!! If it doesn't work I might consider killing myself...

 

[jetjock]

d3fc0n: Glad you got it figured out. Cockpit error eh? I'd ask what bulbs you used but you didn't answer. Using a meter would've also found that very quickly.

For eveyone: The module is different depending on if the CHMSL is incan or LED but you can use either by changing the calibration resistor inside. Years ago, when I changed my CHMSL to a custom stobe unit I designed, I had to do just that so the module would recognize the change in current from the stock incan bulb.

 

[SAWZALL]

d3fc0n: Glad you got it figured out. Cockpit error eh? I'd ask what bulbs you used but you didn't answer. Using a meter would've also found that very quickly.

For eveyone: The module is different depending on if the CHMSL is incan or LED but you can use either by changing the calibration resistor inside. Years ago, when I changed my CHMSL to a custom stobe unit I designed, I had to do just that so the module would recognize the change in current from the stock incan bulb.

So, If you change from the stock 87 lights, to the 89 lights, should you change the light falure sensor from the bright yellow, to the beige sensor?
Just wondering, cause I just installed the 89 lights on my 87, and all the lights are working, just the sensor light on the dash is staying on all the time.
Hope this is the way to ask, as I searched to see if this was covered, and this thread was the closest I seen to my problem. Thanks in advance for any help,.. As I too,.. am a noob here
SAWZ