mk4 Jetta Tail light issues.... anybody else have experience?

[Tkopp]

The tail lights on my jetta are intermiten. I have replaced the brake switch with a new unit. the problem comes when i turn my lights on. generally the passenger side is totally off. i have to pop the trunk, and unclip the board and clip it back in, or i hand to give it a smack to get the lights to turn on.
tonight my brake lights completely quit working. I have replaced all the bulbs, and boards with a spare set, and still nothing, except now, my reverse lights will not turn off, even when it is in 1st, or neutral.

anybody else had similar issues?? im not really sure what to do at this point.

 

[jcrews]

Check for an open ground or loose nut. Pop the carpet off at the left side, and you'll see a ground point on the body panel below the pillar (the rear glass frame). Use an ohmmeter to check resistance from the light bulb holder to that location (brown wire).

 

[coolvdub]

This is a long shot. But check for coolant migration. I doubt that is the problem, but you never know.

 

[Funguy]

I had trouble with the right rear on my '02. Nice state trooper let me know. Turned out that the nuts holding the whole unit in place were loose so that I had been getting moisture in there for a good long while. Cut to Chase: the connector was corroded and I had to spend a good bit of time cleaning it.

 

[Tkopp]

Check for an open ground or loose nut. Pop the carpet off at the left side, and you'll see a ground point on the body panel below the pillar (the rear glass frame). Use an ohmmeter to check resistance from the light bulb holder to that location (brown wire).

I checked the ground under the carpet, its good. I am at a complete loss... the tail lights are getting power, and the reverse and running lights are working, but thats it. i am not sure where to go from here.

 

[burpod]

are you sure the connector is good? it really sounds like frayed wires or bad terminals at the connector to the tail lamp assembly. take them out and inspect them.

and check your reverse light switch ontop of the transmission... that could be stuck.

 

[Tkopp]

I just checked the connector into the light board. Still good, no corrosion.

 

[Tkopp]

Could my BCM (Body Control Module) be bad??

 

[geardriven]

The bcm could be an issue but I suspect you have an issue referred to as "micro fretting" it is becoming a big issue with networked vehicles. Take all connectors apart and put dielectric grease on them. If you have access to a scan tool such as a snap on modis you can control each light individually and view data pertaining to each. Try that and get back to us.

 

[jcrews]

Could my BCM (Body Control Module) be bad??

You don't have one of those. There's a comfort module, but it doesn't have any connection to main lighting.

Dielectric grease is not going to help. Have you actually checked end-to-end ground continuity on both sides with an ohmmeter?

 

[Tkopp]

I checked continuity , and the grounds are good. I think I found the problem. The reverse light switch is bad, and the brake light switch failed. I got a new one, so we'll see how that goes.

 

[fnj2]

1) What in heck do reverse lights and brake lights have to do with tail lights?

2) Dielectric grease is ALWAYS a good idea - whether or not you have other problems.

 

[jcrews]

Incorrect. Dielectric grease is an insulator and is only suitable as a connector gasket lubricant or anti-arc high tension wire boot coating. It should never be applied directly to terminals and will just make a mess.

 

[fnj2]

Laymen have a false idea about press fit electrical connections. The pressure of the contacts cuts through any kind of grease you use. I used plain vaseline on all the connections in one car for 18 years and the electrical system was flawless.

All the grease does is inhibit corrosion, not prevent contact.

 

[Funguy]

Laymen have a false idea about press fit electrical connections. The pressure of the contacts cuts through any kind of grease you use. I used plain vaseline on all the connections in one car for 18 years and the electrical system was flawless.

All the grease does is inhibit corrosion, not prevent contact.

I put dielectric grease in the tail light connector and the whole thing lit up like a christmas tree. I had to clean out all the grease to correct the problem. I am definetly a novice and this really surprised me. I thought the grease would inhibit both rust and moisture while electrically isolating each pin in the connector. I was way wrong

 

[DPM]

if you're already chasing a fault you have no idea whether contact pressure is sufficient to cut through grease...

 

[fnj2]

If the contacts are that loose, it ain't gonna work whether or not you use grease. It's not going to cut through the oxidation either way.

Once again, grease is always a good thing.

 

[PuffinTDI]

Dielectric or conductive

I put dielectric grease in the tail light connector and the whole thing lit up like a christmas tree. I had to clean out all the grease to correct the problem. I am definetly a novice and this really surprised me. I thought the grease would inhibit both rust and moisture while electrically isolating each pin in the connector. I was way wrong

New to the site - hi all ..
Funguy-- is it possible you ended up with conductive grease and not dielectric grease? It would explain what happened and they are on the shelf side by side.


Useful info from a wiki on dielectric grease, and it can cause problems on low pressure connectors, electric conductor lubricant is whats needed...


WIKI Quote
"Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector because it could interfere with the electrical signals passing through the connector in cases where the contact pressure is very low. Products designed as electronic connector lubricants, on the other hand, should be applied to such connector contacts and can dramatically extend their useful life. Polyphenyl Ether, rather than silicone grease, is the active ingredient in some such connector lubricants."


Cheers..

 

[Funguy]

Hey Puffin Welcome. I just ran out to the garage and it is DS-1 Dielectric silicone compound. I am at a loss to understand why it did what it did. Spread it right across the pins in the conector and boom, merry christmas. Cleaned it out with electronic cleaner and all was well.

Maybe I did something funky. Funky is one of my specialties