Turn signal bugaboo (solved)

[JohnD1956]

My 78 wagon has developed an oddity, and I'd appreciate any suggestions from the community.

The turn signals used to work as expected. But this fall they began to operate eratically. They go on and flash, but while in use they slow down and even stop occasionally. You can see in the indicator that the pulse is off as well as they slow down. There will be an intermittent flash which is represented on the dash indicators as well as the external bulbs. The factory 4 ways work perfectly.

Here's what I've done so far:

Replaced the flasher unit. removed the tow hitch wiring connection entirely. Cleaned and reset all the grounds and made sure I had all the correct bulbs. I also inspected all the wiring thats visible and nothing is cut or indicating any short or arcing. According to the manual there is no relay in the circuit, just the signal light switch in the column, the flasher, and the wiring.

Any ideas?

Edited January 6, 2011 by JohnD1956
solved the problem (see edit history)

[Guest papaw]

Check the switch itself in the column. I have seen the little brass contacts get worn were they do not make a good contact. I had one that had a week spring under it and replaced with a shorten ball point pen spring. It worked, for how long I don't know as I sold the car shortly afterwards.

[JohnD1956]

Good idea Neil, I'll have to look at that.

[NTX5467]

There is a ground for EACH side of the front wiring harness. Possibly the same at the rear, too.

Conventional wisdom would suggest a flasher issue, but it could also be a voltage issue. As the flasher works on current flow heating a bi-metal spring, little current flow can result in slower flash intervals. Higher resistance is the opposite.

An interesting problem!

Just some thoughts,

NTX5467

[JohnD1956]

NTX, What you said is interesting in that the erratic pulsing of the unit exhibited the following quirks.

While I was working on it today without the motor running, more than once the flasher would work for five cycles and then stop, with the unit in connect mode ( so the signal light was on). Switching the signal lever to the other directional resulted in no flashing , just the light on. Later, on an errand run, the signals alternated, sometimes only flashing 5 times, other times flashing more. So it sort of follows what you said about low voltage.

I did find a separate section in the manual about trouble shooting this and that section indicates a possible loose connection at the connector on the steering column. Another thing not so easy to get to in this particular car. It suggests attaching a new switch for testing before dismantling the steering column. I will begin looking for a new switch.

I did find the ground on both sides in the front. Being a wagon, the convenient ground in the rear was in the spare tire well. That opposite interior panel back there is not so easy to get off, but I'll take a shot getting it out to check for another grouond back there too..

[Dandy Dave]

Every once in a while a light bulb will fail internally and drive you nuts. It causes a "back feed" in the system. The fillament will break and cross with the second fillament, or cause a short. I would walk around and change out some of the bulbs just to be sure that it is not a fault with the bulbs before pulling the steering columm apart JD. Dandy Dave!

[Guest Jim_Edwards]

I would also be looking at the inside of the bulb sockets. The tin/lead solder type contacts will often corrode and create a short between themselves or an open for the bulb contact. The latter reacting exactly the same as a burned filament. Find white powdery looking stuff in any of the sockets and you have likely found the source of the problem. A small brass bristle brush and a shot of air should take care of it.

Jim

[Oldsfan]

I had a '68 Delta that used to do the same thing. They found a bad ground wire in the harness in the trunk.

Paul

[JohnD1956]

Thanks for these ideas. I have checked the sockets, but I have a coat of white lithium in each and none show a sign of corrosion. ( does anyone think it could be this grease causing the problem???)

When I removed the wiring harness for the tow hitch I merely cut the wires and capped the ends. Today I eliminated the aftermarket connection for the ground. The flasher worked longer but is still erratic. I don't know if you should hear the click and the lights flash at the same moment, but today I could hear the click and see the flash separately. I think I will try another new flasher just in case. They are certainly cheap enough.

I'll take another look at the bulbs too. And I still have to get that other rear panel off to see if there is a second ground in the back. Thanks again for the ideas.

[NTX5467]

pfloro . . . it used to be that signal flashers were rated as to the number of light bulbs in the circuit. More bulbs meant more current flow, so to maintain the desired 1 flash/second, it took a heavier-duty bimetal spring contact to make that happen. If you used a lighter-duty (fewer total bulbs, as in one or two) flasher, with the larger number of bulbs, current flow would be too much for the lighter bimetal spring contact and the flasher would cycle much faster (heating and cooling cycles of the bimetal spring) than desired. Or, if the flasher was correctly sized, if the faster flash rate was noticed, it would indicate some "high resistance" situation on that particular side of the vehicle--think bulb or socket with high resistance in it, or a high-resistance connector somewhere . . . including the bulkhead connector (as mentioned previously).

In my '77 Camaro, when a front turn signal light doesn't work, it backfeeds through the gauge cluster's turn signal indicator lamp, finding a ground in that circuit. It can also be a flaky wiring connection, too--been there, done that, why I don't like butt connectors instead of male/female terminals.

In many cases, a light tan "grease" has been found in "virgin" (i.e., not disassembled since factory assembly) light sockets, usually on the rear of the car. Not the clear/waxy dielectric grease like you'd use on spark plug boots (or hood bumpers to decrease rubber squeaks).

It's not unusual, given the nature of the heat/cool cycles of the bimetal contact in the flasher, for flash cycles to be a little irregular, but not completely stop. As it did not matter which turn signal position the switch was in just means that the same flasher controls each side. A circuit test would be to see how things work with the emergency flashers (which seem to be able to "push" and work every light bulb that CAN light up, still with some slight flash timing variations.

I believe that you might be able to find some transistorized/electronic turn signal flashers to fit the older vehicles. GM started using them in production in the 1990s, but with a different wiring harness plug-in. This might be an option (one with the correct plug-in for the earlier vehicle). This would be different than the "no load" flasher that must be used with the aftermarket LED light bulb replacement panels.

Keep us posted, please.

Just some thoughts,

NTX5467

Edited January 6, 2011 by NTX5467 (see edit history)

[JohnD1956]

Well, it turns out I mistakenly replaced the flasher for the 4 way unit instead of the one for the signal lights. Luckilly I saved the original flasher when I did this and it was interchangeable with the signal flasher.

For those who are interested, the two flashers are attached to the fuse box in this year, and the 4 way flasher is the one in the upper left corner ( the hard one to replace I might add.) The signal flasher is the one in the lower right corner.

I should have checked my manual before I changed the flasher originally. Closed books impart no knowledge.

Once again, thanks for the assistance with all your responses.

[Rich Morton]

Glad to hear you were able to solve your problem.Those types of things can really SCRAMBLE your brain!:confused::eek:

[Dandy Dave]

Those are a two prong unit in the GM's of that vintage. I've been there and replaced a few of those myself. And yes, there are two. I guess that we all assumed you knew that. Glad you have it solved JD! Dandy Dave!

[JohnD1956]

I'm glad they work too, I really did not feel like tearing into wiring outside in a northeast winter. I knew there were two flashers all along, but what threw me off was that you can feel the clicking action of each flasher in both units at the same time. Without reading the manual I guessed the wrong flasher first. Not much of a defense, but it's what happened.

Meanwhile I was amazed at some of the other suggestions posted here by others. Things I did not even consider. Sure makes the forum that much more valuable.