Blinker troubleshooting - '81 SC

[kger]

I'm working on the last couple issues on my SC, and am finally getting around to addressing some funky blinker operation.

Hoping someone can help get me started troubleshooting this since electronics is where I get lost fastest.

Problem 1: Driver's Front blinker does not light. I swapped the bulb, no luck. Relay is clicking and the rear bulb flashes normally (well, see Problem 2)

Problem 2: Driver's Rear blinker also triggers the DR brake light, though it blinks slightly delayed from the turn indicator bulb.

Other info
-All bulbs are fresh
-All fuses seem to be intact
-I have not pulled out the multimeter yet, but I do have one and am not 100% clueless with it.

Could someone walk me through their sequence for running this down, especially Problem 1 (problem 2 I can live with)

Thanks!

[Bill Douglas]

With weird electrical problems the first thing I do is clean and reconnect the ground/earth.

[brianlay]

the front directionals are fused, the rears are not.
You said the fuses look ok but I would put a meter, or 12V test light, on each side of the fuse.

The fuse or holder could have a bit of corrosion.

If you have voltage there then it must be the wire going to the lamp, or the lamp socket that is the problem.
Could be the ground connection but if the parking light works then it's probably ok since they share a ground

[David Inc.]

Those fuses lie. I've replaced three fuses in my car that were all visually fine (including front left blinker). Swap the front blinker fuses with known good ones.

[PeteKz]

If you have never swapped ALL the fuses with new ones, do that now. It may or may not fix this problem, but it will prevent future ones that will have you gnashing your teeth. Fuses get old, brittle, and then crack from many heat cycles.

[Matt at Pelican Parts]

As others have stated it seems like an issue that may be rooted in the harness or connector itself with corrosion being the biggest factor.

The mutlimeter isn't tough to get the hang of if you're just checking to see if you've got a full 12v or not.

[kger]

Dove into this tonight, here are my observations (it gets weirder):

-I replaced all fuses and cleaned the contact points on each slot, and check continuity across each terminal, all good.
-I check all terminals with a test light with ignition on and off and all seem in working order
-With the ignition on and blinker stalk switch engaged, the blinker and parking light terminal get intermitent power with the relay clicks
-Still no blinker (from either turn signal or parking light)

Strange stuff:
-With ignition OFF and blinker stalk switch engaged left, the left parking light and rear blinker light come on and stay on solid (no blinking, no relay switching)
-With the ignition ON and headlights on (both low and high beams), the parking light will blink with the stalk switch engaged, albeit slowly
-Binker light never comes on, parking light does under those two circumstances.

My guess is the blinker housing or wiring could be faulty, need to check that. But I'm not sure how to explain the strange parking light functions.

Any new thoughts before I just go end to end on these circuits or take it to a shop?

[PeteKz]

I'll reinforce what others have said about grounds. Those old signal housings get corroded and the grounds get intermittent and bad. When that happens, current loops from the signal lights back through the other lights or wires, instead of grounding to the housing, which in turn must be grounded to the car. I spent a fair amount of time chasing similar problems several years ago in my 1973 car.

One more time: Grounds. They may or may not be the only problem, but likely are part of it.

[spoke]

Originally Posted by kger

Dove into this tonight, here are my observations (it gets weirder):

-I replaced all fuses and cleaned the contact points on each slot, and check continuity across each terminal, all good.
-I check all terminals with a test light with ignition on and off and all seem in working order
-With the ignition on and blinker stalk switch engaged, the blinker and parking light terminal get intermitent power with the relay clicks
-Still no blinker (from either turn signal or parking light)

Strange stuff:
-With ignition OFF and blinker stalk switch engaged left, the left parking light and rear blinker light come on and stay on solid (no blinking, no relay switching)
-With the ignition ON and headlights on (both low and high beams), the parking light will blink with the stalk switch engaged, albeit slowly
-Binker light never comes on, parking light does under those two circumstances.

My guess is the blinker housing or wiring could be faulty, need to check that. But I'm not sure how to explain the strange parking light functions.

Any new thoughts before I just go end to end on these circuits or take it to a shop?

About strange stuff: With ignition off and turnsignal stalk engaged left is a designed feature I think for some kind of European parking light.

What parking light are you referring to? Is this the front sidemarker or rear sidemarker?

[spoke]

Originally Posted by kger

Problem 2: Driver's Rear blinker also triggers the DR brake light, though it blinks slightly delayed from the turn indicator bulb.

Driver's rear turnsignal only shares a ground with the driver brake light. It sounds like your ground is not connected. When the driver brake light blinks with the driver turnsignal, do both filaments of the brake flash? It's difficult to see the filaments flashing but not impossible. You'd have to have the lens off at this time.

I'm assuming the brake does not have a ground and both filaments are lighting up. They may seem delayed because 2 filaments in series across some voltage may take some time to light up; thus a delay.

[kger]

More progress on this last night. I opened the lenses for both front blinkers and got out the test light.

Good news: The LF blinker bulb socket is getting good power from the relay when the stalk switch is engaged. It will blink a test light which is grounded to the - batt terminal, and appears to be getting an intermittent 12v.

I assume this means I have a bad ground from the socket, correct?

If that is true, what is the best way to fix that? Do I need to remove the bumper and turn signal housing and inspect each wire, or should I ground that contact somewhere else?

With a test light, test probe and multimeter, what is the general proceedure for testing good ground continuity for this circuit?

Thanks!

[kger]

Read the wiring diagram in the Bentley manual which led me to the L headlight bucket and I think I found my issue. The point where two wires from the turn signal (I believe) connect to the headlight bulb socket are FRIED.

Can anyone confirm what I'm looking at? Is this the ground circuit for the turn signal bulb? How do I fix this? Replace the bulb socket and repair the fried wires and reconnect?

[wazzz]

Yes, fix it anyway. Replace socket and reconnect wires, shortening them a bit if necessary in order to clear the brittle part and reach shiny copper strands.

Socket looks more cooked than fried, and so do the wires. No trace of shorting but more like the result of excess of heat from the bulb and heat from poor contact (resistance) due to aging and corrosion.

[kger]

That was it. New h4 socket and cleaned up the connections in the blinker and good as new. The connector was totally fried at the ground socket. Melted black carbon, couldn't get the bulb out without destroying it. I switched to a lower power bulb just to be safe.