Blinkers not working

[ih8vols]

Hello! I have a 79 Silverado Step side. I just completed an LS swap in the last week or so.

Drove through the neighborhood some today to test everything out before getting on the main roads and noticed my blinkers aren’t working.

When I flip them on - the front lights will come on once and the dash indicator will light up once. Rear lights don’t come on at all.

My backup lights do come on and work fine.

We didn’t touch anything ok the swap that should have impacted the blinkers though we did find some bizarre wiring throughout the truck. Blinkers work d fine in the past.

Any suggestions on where to start troubleshooting? Thanks!

[bd]

With the rear bulbs not illuminating the flasher probably doesn't see sufficient load to flash.  Do the brake lights work?

[ih8vols]

Yep, brake lights work.

Could it be a bad ground? Would that only impact the blinkers?

[bd]

Remove the flasher from the fuse box and temporarily jumper the flasher socket.  Switch the ignition on.  Will the rears light up with the turn signal switch?

[ih8vols]

Remove the flasher from the fuse box and temporarily jumper the flasher socket.  Switch the ignition on.  Will the rears light up with the turn signal switch?

Hello. Quick update and more questions...

First (dumb question)- When you say to "temp jumper the flasher socket", what should I jump it to?


This weekend I did some troubleshooting. I tried a new flasher on Saturday morning to see if it was that easy of a fix, and there was no change.

Took the truck for a quick drive on Saturday afternoon and tried the blinkers, and the left signal worked perfectly. The right signal would work for 1 blink and then stop.


Sunday morning, I took the truck for the same 2 mile loop and both blinkers would only flash once. After going back and forth between the two about 3 or 4 times, neither would do anything afterwards.

I peeked in the steering column to see if any wires were pinched, and all looked fine.

I then went through the grounds on the rear harness and cleaned the contacts real good. No blinkers work again.

[JohnnyPopper]

The flasher has two connections-one from 12v and the other out to the lights.

When current passes through the flasher it heats up an element that opens and closes causing the 'blinky blink'

When you jump the two connections your signal lights should turn on and stay on because there's no blinky box thingy in line.

make the jump then turn on the ignition, if all is well with your truck, you should see the lights on solid. No blinky.

[bd]

The truck has two separate flashers.  One is for the turn signals and the other is for the 4-way hazard flashers.  Did you replace the correct one? 

Do both rear lamps illuminate brightly when you step on the brake pedal?

Do you have an incandescent test light?

[ih8vols]

The truck has two separate flashers.  One is for the turn signals and the other is for the 4-way hazard flashers.  Did you replace the correct one? 

Do both rear lamps illuminate brightly when you step on the brake pedal?

Do you have an incandescent test light?

I'm 99% sure I replaced the correct one. My truck still has the factory labeling on the box. I replaced the lower right side one.

Yep, everything lights up brightly and as expected.

I do have a test light.

[bd]

Did you do this?  What was the result?

Remove the flasher from the fuse box and temporarily jumper the flasher socket.  Switch the ignition on.  Will the [left and right] rears light up [consistently] with the turn signal switch?

[ih8vols]

I did not get a chance to do your test. I did get to take a video tonight.

Here’s what I noticed tonight - if I push the lever quickly and hard, the in cab blinker light comes on much stronger. When I raise or lower the lever slowly, it’s very dull.

Having headlights on did not impact how the blinkers reacted.

I did notice that when the blinkers were on, the side front flashers would dim a bit and stay dim until the blinker was turned off.

Here’s my video. I’ll try to do your test tomorrow. Thanks for the help!


https://drive.google.com/file/d/1-I_q0fdWSzwV4dMA53wXIpo8GJ-YFHNr/view?usp=drivesdk

[ih8vols]

I was able to the test today. When I connected the jumper the lights stayed on solid when I turned each side on. They were solid and bright as I would expect. I pressed the brakes and tried it and got good results.

Does this mean the wiring from the fuse box to the bulbs are good and the problem is between my steering column and box?

Did you do this?  What was the result?

Remove the flasher from the fuse box and temporarily jumper the flasher socket.  Switch the ignition on.  Will the [left and right] rears light up [consistently] with the turn signal switch?

[bd]

Try another flasher.  Or switch the hazard and turn flashers and try that.  Use an electronic flasher instead of the original thermal type (e.g., EL12 Novita 20-amp or similar).

[ih8vols]

Try another flasher.  Or switch the hazard and turn flashers and try that.  Use an electronic flasher instead of the original thermal type (e.g., EL12 Novita 20-amp or similar).

Hello. I bought the Novita EL12. I put it in the blinker spot and there was no change. I pulled the hazard lights relay out and put it in the blinker spot and it works perfectly. I put the Novita into the hazard spot and it works as well.

Any idea why this would happen? I appreciate the help! So simple but I would have chased it for a while. Thanks!

[bd]

Perhaps surface oxidation of the flasher socket brass terminals, or socket terminals that are failing from metal fatigue, or burned crimps between the copper wire and the brass terminals on the backside of the fuse box, or a wire that is severed inside its sheath(?).  There is a myriad of possibilities.  Intermittent electrical problems can be a pain to diagnose; everything has a habit of working properly when you perform your tests, only to fail when you're out on the road.  LOL

Nonetheless, accurate diagnosis is recommended to resolve mysterious symptoms while the vehicle is in service.  You may need to separate the fuse box from the firewall bulkhead connector and physically inspect the condition of the wiring behind the fuse box.  If you are unable to accurately diagnose the problem with a test light you may be forced to start disassembling and look.

The 1979 Wiring Manual will prove invaluable to your quest.  It's your friend.