Do I really need turn signals after dark???

[Al_C]

I brought my car home from Bloomington almost a month ago. I've had a few good days to get out and drive, but not as many as I'd like. Man, it's cold this spring! That also is making it harder to get my small list of finish items done. I'd prefer to work in the garage without heater, hat and coat...

Anyway, let's get to it. One of the items on my list is driving me crazy. My turn signals do not work when the headlights are on. Maybe you can help. But first, let's set the stage.

Headlights, parking lights work.
Brights work.
Brake lights work.
Backup light works.
4-way flashers work (when the headlights and/or parking lights are off)
Turn signals work (when the headlights and/or parking lights are off)

When I turn the headlights on, the turn signal indicators light up.

I have the RT turn signal installed, and the momentary switch is wired to turn the brights on/off.

I think the turn signals worked originally, but I didn't drive it much after dark prior to going to Indiana. So, I really can't be sure. In any event, while the car was with Jeff K., I went and swapped out the dashboard. As you can guess, that entailed disconnecting just about every wire for the turn signals (because of the RT setup). I marked each wire to ensure they were properly connected when I reassembled everything. When the swap was completed, Jeff and I tested everything and it worked. However, we did not test the turn signals with the headlights on. (Of course, there were no headlights connected as the body was off...)

I tried removing each of the turn signal / parking light/ tail light bulbs, one at a time, to see if that would have an effect. It didn't. I'd like to figure this out without having to pull the dash, as that would be less than fun with the body in place.

Here's where you come in. Got any idea what might cause this problem? Got any good troubleshooting tests I can try that would narrow it down? maybe you've run into something similar yourself? Then again, maybe I can get away without having them work - there's nobody on the road anyway! Thanks in advance!

[Dagwoods]

Hey, this sounds familiar. Although if you are experiencing it with all four turn signals, I don't think it would be the same.
https://thefactoryfiveforum.com/showthread.php?34972-Turn-signal-wiring-issue

[Avalanche325]

Just move to Florida. Nobody here uses them.

.....drives me nuts.

[Railroad]

Just maybe, your turn signals are grounding through your headlights.
Put a dedicated ground on your turn signals.

[FLPBFoot]

Just maybe, your turn signals are grounding through your headlights.
Put a dedicated ground on your turn signals.

Was thinking the same thing. Maybe have a ground in the running lights and turn signals messed up.

[rich grsc]

Turn signals shouldn't be connected with the headlights, so it would be a ground issue.

[Just puttering]

Disconect the turns at the switch and try the lights.

Turns stay off - you are feeding them power up stream of the switch - unlikely

Turns come on - you are feeding them power down stream of the switch

Also, disconnect the hazard flasher switch, and test

As stated above when you turn on the headlights that power is going to the turn signals also, consider that the left and right turns are actually a separate circuit, so both lighting up points to a problem with the flashers circuit that runs both sides at once.

Get to the point that you can only turn on the headlights on with the other switches disconnected and then work back attaching flasher and turn switches and you should narrow down the cross over!

[Ray]

Do you have a FFR or "C&^%a" emblem on the car? Change it to a BMW emblem and then the lack of turn signals would be expected.

Ray

[Al_C]

some great input here! I love the BMW reference, as well as the Florida reference. Those will be last resorts...

Yes, I agree that it must be a ground issue. First thing I will do is re-check my ground from the Russ Thompson switch. It's grounded to the frame, but maybe the connection is insulated somehow.

Just Puttering - I like your ideas, I just have to figure out how to do them all. the hazard switch is easy. the turn signals, not so much. I can reach up under and disconnect one of the leads off the switch - that may do it.

Actually, the hazards weren't working as two of the leads came off the switch. The net effect of that was that the hazards didn't work.

I will try these things in the morning and post my results. Please keep your ideas coming!

[Boydster]

I know you said you removed and replaced the lamps one at a time, but revisit this... Its easy to install a dual element lamp in the wrong position, and this would allow running light power (when headlights are on) to power the brighter turn signal element, backfeeding into the indicators. Take all 4 lamps out and then try it. The lamps is the only place that headlight / running light power and turn signal power come together.

[Big Blocker]

Just an observation from your post above; First thing I will do is re-check my ground from the Russ Thompson switch. It's grounded to the frame, but maybe the connection is insulated somehow.

To the best of my recollection, nothing is grounded on the Russ Thompson switch assembly. There are three wires that control the TS system, flasher feed in, right out and left out. NO ground for the switch function.

The push button [momentary] at the end of the stalk can be grounded if used to control a relay for headlights or horn but under normal conditions, isn't grounded by itself - wiring is; power in and power out . . . This push button is NOT part of the TS system.

Doc

[Al_C]

Just an observation from your post above; First thing I will do is re-check my ground from the Russ Thompson switch. It's grounded to the frame, but maybe the connection is insulated somehow.

To the best of my recollection, nothing is grounded on the Russ Thompson switch assembly. There are three wires that control the TS system, flasher feed in, right out and left out. NO ground for the switch function.

The push button [momentary] at the end of the stalk can be grounded if used to control a relay for headlights or horn but under normal conditions, isn't grounded by itself - wiring is; power in and power out . . . This push button is NOT part of the TS system.

Doc

I stand corrected. Doc is right - the only ground is from the momentary switch. We'll get to that in a minute.

Here's what I've tried so far today:
1. took the two bulbs out of the front turn signal/parking lights and everything works the way is is supposed to.
2. put the front bulbs back and removed all four of the tail light bulbs. result is the same as the initial problem - turn signals don't work with headlights on. And, the license plate bulb flashes. (that was interesting)
3. removed the 6 bulbs. nothing flashes, but the indicators light up correctly.
4. the momentary switch ground is properly connected.

I had a good conversation with Ducky2009. He asked me about the diodes I'm using. My reply was "I'm not using any diodes". He may have hit on it, yes? I have one relay in play: to enable the stalk button working as a momentary switch to dim the headlights. Of course, that raises the question as to why I never installed one, other than my understanding at the time was that I didn't need it.

Will a diode solve the problem? (David and I are thinking yes).

Check this: the diode will be attached to the wire that goes from the Russ Thompson switch to the VW relay. Yes/no?

[Big Blocker]

IF you are using the readily available circuit using the "VW relay", there are diodes (5) in the circuit, especially if you are using only one dash indicator. (drawing supplied below).

https://i.postimg.cc/cCBp4j2v/47-26.jpg (https://postimg.cc/YLjndXp7)

IF you have individual dash indicators, I don't believe the diodes are required as they can be connected to each front TS light and won't interconnect.

Doc

[Al_C]

IF you are using the readily available circuit using the "VW relay", there are diodes (5) in the circuit, especially if you are using only one dash indicator. (drawing supplied below).

https://i.postimg.cc/cCBp4j2v/47-26.jpg (https://postimg.cc/YLjndXp7)

IF you have individual dash indicators, I don't believe the diodes are required as they can be connected to each front TS light and won't interconnect.

Doc

Yes, Doc, you confirmed my understanding. I have the same picture that you included above. I have one relay and two indicator lights. No diode. That's what I thought should be done, so either I need the diode indicated just to the left of the label "flash to pass", or my problem lies elsewhere.

No more Radio Shack, so I ordered a bunch on line. I'll give that a whirl as soon as it gets here, unless someone comes up with additional possible causes. Thanks!