Turn signal and brake light issues!

[TLangM998]

Alright guys, newbie here, so go easy on me! I have a 1987 M998 and I am having issues with the turn signals and brake lights. The brake lights don't light up at all, in stop light or service drive positions. When it turn the signals on in the stop light position, the lights stay illuminated with a faint flash turn signal, where the lights should not be illuminated at all. I checked all the grounds and they seem to be good. When in service drive, with the running lights on, it does the same faint flash. Any body have any ideas? Thanks in advance!

 

[1 Patriot-of-many]

I'd suspect triswitch and probably buy a new one. But before I did buy a new switch I'd make sure the connector is screwed on tight to the switch then if it was I'd unscrew the connector on the rear, make sure the connections are all clean and apply just a TOUCH of dielectric grease to each hole(make sure you wipe off any excess to prevent cross pin electricity), and then make sure the connector is on nice and tight. I believe the cable is always live so might be a good idea to remove negative ground from the battery first. I'm not sure how the turn signal switch interfaces with the light switch, that'd be next on my list though. Brain fart as noted below, it's a sealant, nonconducive, don't use to much though is the idea.

 

[Mario]

Why would you need to wipe off dielectric grease? It's non conducive.

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[1 Patriot-of-many]

Doooooh, right. brainfart.

 

[TLangM998]

I'd suspect triswitch and probably buy a new one. But before I did buy a new switch I'd make sure the connector is screwed on tight to the switch then if it was I'd unscrew the connector on the rear, make sure the connections are all clean and apply just a TOUCH of dielectric grease to each hole(make sure you wipe off any excess to prevent cross pin electricity), and then make sure the connector is on nice and tight. I believe the cable is always live so might be a good idea to remove negative ground from the battery first. I'm not sure how the turn signal switch interfaces with the light switch, that'd be next on my list though. Brain fart as noted below, it's a sealant, nonconducive, don't use to much though is the idea.

Thanks! I'll tackle that tomorrow and let you know how it goes!


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[TLangM998]

Also, what's the triswitch?! Ha!


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[buffalorunner]

After just tackling a similar issue, try making a jumper wire so that both rear bolts that hold the taillight housing are grounded. The bolts on the left complete the circuit for brake lights and running lights, and the bolt on the right completes the circuit for the black out lights and brake lights. Often the metal plate behind the tail light is not sufficient as a jumper for the ground, or not present do to negligent install.

Also make sure you have sufficient power at the rear. I find a simple voltage probe with an incandescent light helps the most, that way I can see the bulb get brighter when I am testing the brakes when I complete (short) the brake light circuit.

 

[Bulldogger]

Go for the easy fix first. Unplug and replug all connections, especially the big screwed on connection on the back of the light control panel.
Sounds more like loose connections and bad fittings than anything else. I also have a 1987 and my brake light switch was bad. Found another quickly online.
Bulldogger

 

[shawnshumvee]

MY turn signals work fine, My tail lights work fine and my brake lights work fine but only if i press the pedal very HARD!! I'm thinking break light switch? But just wondering if anyone had this issue and or is there an adjustment on the switch? I mean i apply the brakes normally (like coming to a stop sign) and they don't light up! But if i SLAM the brake and hold it to the floor (very Hard) then the brakes light up.

 

[TLangM998]

MY turn signals work fine, My tail lights work fine and my brake lights work fine but only if i press the pedal very HARD!! I'm thinking break light switch? But just wondering if anyone had this issue and or is there an adjustment on the switch? I mean i apply the brakes normally (like coming to a stop sign) and they don't light up! But if i SLAM the brake and hold it to the floor (very Hard) then the brakes light up.

There is an adjustment! TM 9-2320-280-20-2, sections 4-60 and 4-61 cover the adjustment process.


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[Bulldogger]

Agreed, try to adjust the switch attached to the pedal arm and see if that helps.
Bulldogger

 

[Action]

yup. Move the switch closer to the seat, so it will be activated sooner.

 

[shawnshumvee]

Thanks guys! I got the lights working. Now the brake lights activate will 4-6 pounds of pressure. I also attached a few pictures so if some one else comes across this issue it will save a little time, because searching the TM"S isn't very fast, although its faster for me because i made hard copies of the TM's because searching the TM's as a PDF file sucks big time! I prefer hard copy anyway!

 

[Dawelcher]

I have a m939a2, my service lights all work fine but I have no brake lights when pressing the brake, I replaced the brake light switch already and no luck. Any other ideas would be a great help.

 

[papakb]

What was the failure mode? Were they working and just failed? There are lots of failure points, bad master light switch, burnt out bulbs, bad taillight ground.....It might be a good time to throw in a couple of 10-30 volt LEDs.