Tail Light Turn Signal Issues

[bliss]

Originally Posted by patrickt

Yes, these are two fuses that are separate from the fuse blocks in the engine compartment. These two fast-blow fuses are located on the steering column, right above where your knees are when you are driving. First, examine them, then if they look like they're ok (meaning one is not blackened with an obviously blown filament), then pull them both out and switch them, then put them back in. See if that makes any changes. And while you're doing that, with the ignition key on, put your foot on the brakes and tell me if both, or only one of the brake lights is coming on.

What ERA number is your car? Perhaps the really early ones didn't have the fuses. I'll check the schematic for your car number and see.

EDIT -- It looks like they put the fuses in around car 335.

Thanks - mine ERA is 098 - very early - so, no separate fuses?

[patrickt]

Originally Posted by bliss

Thanks - mine ERA is 098 - very early - so, no separate fuses?

No separate fuses. Your next step will involve either using a VOM (cheapy little volt ohm meter) or a 12 volt test light. Sound ok? And what was the result of checking your brake lights to see which bulbs work?

[patrickt]

Here, I did a five minute cut and paste on your car's wiring diagram so you can see what you are dealing with. Since your front flashers work, you know that your signal wand switch, and the flasher unit, are both probably working properly. Your brake lights and signal lights use the same filament. So, from that, you can surmise that:

1) If your brake lights are working normally, then you know the connections from the trailer relay to the rear bulbs are good, including the grounds.

2) If your brake lights are also misbehaving, then it could be either the trailer relay, or the connections between the relay and the bulbs, that includes the grounds.

You will need to test the voltage, using a VOM or test light, coming out of the trailer relay, on both the yellow and green wires. If those readings are good, then you will test the wires as they go in to the bulb fixture itself (note that it appears the wire colors change). If we have to, we'll also check the wires going in to the trailer relay and maybe use a 12v jumper wire to test the bulb circuit itself. The way you will check the wires is to carefully scrape a little bit of the insulation off of them, using a razor, so that you can see the copper conductor. This is really not hard at all.

If I had to guess, I think it's going to end up being either a bad trailer relay or a bad connection (that includes a ground).

[DanEC]

Originally Posted by patrickt

Your brake lights and signal lights use the same filament. So, from that, you can surmise that:

Patrick - is this right? I'm pretty sure mine have two filiments - at least the fronts do I'm certain - I think the rear are the same. Or is this a different bulb the early car used?

[patrickt]

Originally Posted by DanEC

Patrick - is this right? I'm pretty sure mine have two filiments - at least the fronts do I'm certain - I think the rear are the same. Or is this a different bulb the early car used?

The tail lights, "parking lights" or "running lights," as some call them, that are on all the time for night driving, use one of the two filaments. The turn signals and brake lights use the second filament. That's the whole purpose behind the trailer relay. If the turn signals and brake lights used different filaments, then you wouldn't need the trailer relay to "marshall" the current when you had both your foot on the brake and were signalling a turn. Look at the schematic and you can see that each bulb only has one output coming from the trailer relay. That one output has to control both turn signalling and brake signalling.

The front lights also have two filaments, but since there are no "front brake lights," it doesn't matter and, thus, needs no relay to sort it all out.

[DanEC]

OK - forgot for a minute there the three modes of operation at the tail.

[bliss]

Originally Posted by patrickt

Here, I did a five minute cut and paste on your car's wiring diagram so you can see what you are dealing with. Since your front flashers work, you know that your signal wand switch, and the flasher unit, are both probably working properly. Your brake lights and signal lights use the same filament. So, from that, you can surmise that:

1) If your brake lights are working normally, then you know the connections from the trailer relay to the rear bulbs are good, including the grounds.

Lights OFF - both brake lights work;

Lights ON - both brake lights don't work (along with the flashers on both sides), although the tail lights do work.

2) If your brake lights are also misbehaving, then it could be either the trailer relay, or the connections between the relay and the bulbs, that includes the grounds.

Therefore, based on response to item 1 - it appears to be the 'trailer relay' or the connection between the relay and the bulbs, including grounds!


You will need to test the voltage, using a VOM or test light, coming out of the trailer relay, on both the yellow and green wires. If those readings are good, then you will test the wires as they go in to the bulb fixture itself (note that it appears the wire colors change). If we have to, we'll also check the wires going in to the trailer relay and maybe use a 12v jumper wire to test the bulb circuit itself. The way you will check the wires is to carefully scrape a little bit of the insulation off of them, using a razor, so that you can see the copper conductor. This is really not hard at all.

If I had to guess, I think it's going to end up being either a bad trailer relay or a bad connection (that includes a ground).

I'll need help from my brother to test the lines, etc.

Trailer Relay - These units are apparently available at auto stores - is there are top choice product or will any one do just fine?

BTW - you sure are being very helpful - thank you, thank you very much!

[patrickt]

Originally Posted by bliss

Trailer Relay - These units are apparently available at auto stores - is there a top choice product or will any one do just fine?

You know, they're probably all made by the same people in China that make everything else in the world. I think they're technically called "Tail Light Converters" and you want a three in to two jobbie. Like this:

Originally Posted by bliss

BTW - you sure are being very helpful - thank you, thank you very much!

RodKnock says I do this once or twice a year to balance off the fact that I provoke and irritate people the rest of the time. His theory is that I provide just enough helpful advice to keep Jamo from booting me out of this place.

[DanEC]

If you have problems locating the trailer relay locally they carry them at Summit and Summit ships quickly.

[patrickt]

I read some of the Amazon reviews of some of the cheaper 3 to 2 converters and some of the guys there complain of the huge voltage drop in them (which makes your lights dim). This one claims to be "heavy duty" and to put out six whole amps of current. Who knows. If Bliss is lucky, it'll just turn out to be a bad connection or almost-broken wire.

[ame="http://www.amazon.com/Trailer-Heavy-Duty-Taillight-Converter-5423203/dp/B00MJUPD60/ref=sr_1_1?ie=UTF8&qid=1412129305&sr=8-1&keywords=stag+trailer+converter+3+to+2+heavy+dut y"]Amazon.com: RV Trailer Camper Heavy-Duty 3-2 Solid State Taillight Converter 5423203: Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/41F17OWUw8L.@@AMEPARAM@@41F17OWUw8L[/ame]