Alternating rear hazards

[84gmcsierra]

I have an 84 Sierra 2500 that's having some rear light issues. Left side brake, tail lights work but the right side is dim, slow blinking and when the hazards are on, they alternate like a police car. Fronts on all work as they should. I'm guessing it's a grounding issue? I have a new turn signal switch to install yet.

 

[CleanSump]

I have an 84 Sierra 2500 that's having some rear light issues. Left side brake, tail lights work but the right side is dim, slow blinking and when the hazards are on, they alternate like a police car. Fronts on all work as they should. I'm guessing it's a grounding issue? I have a new turn signal switch to install yet.

It does sound like the multipurpose switch (aka turn signal switch) has gone wonky. I had a 1980s Mercedes do that and the fix was the new stalk/switch combo.
Oh, I just remembered my 1997 Blazer did it too. There was also a flasher switch on the top of the steering column of the Blazer than just decided to turn on by itself. I replaced that thing twice in 12 years.

 

[BC1]

I would look for the reason one is dim first. Could be a ground problem and fixing that may sort the other issues.

 

[84gmcsierra]

I'll spend some time under the truck tomorrow. I did replace both taillight housings a couple years ago but they were fine until last year. I'll see if I can get the harness out and look for mud/dirt in the connectors as well as any breaks.

 

[paulo57509]

Check the bulb sockets in the dim light assembly. I've had wonky light behavior, traced to the bulb sockets.

I had an '88 E150 where the turn signal lamp and indicator were steady-on, but super dim; no brake or indicator use. The only way I noticed was at night. DMM didn't show me anything, other than there was voltage present that shouldn't be there. I replaced the socket (1157) and the issue went away.

Finding a Ford replacement socket was another story. https://bobistheoilguy.com/forums/threads/ford-pigtail-catalog.357046/#post-6169556

 

[meep]

In my mind, this is 90% a socket connection or ground issue

 

[The_Jeff]

Grounding, sockets, or a bad filament in a two filament bulb shorting to the other system.

Had this exact thing happen with a square body back in the day.

You'll notice the bulbs are not 100% of their possible brightness, either. Current is going in weird directions. Check "dumb" stuff like marker lights and even the "normal" functioning front turn signals & markers. If you have an accidental series connection between a big bulb and a marker, the marker will use 95% of the power and the big bulb, 5%.... Ohm's law.

You'll probably also notice that if you have everything on and remove an "unrelated" bulb, some other bulbs will be affected.

Also if you have a trailer connector, check that for drama.

 

[supton]

As a kid I removed the bed on my pickup so as to fix the frame, and I taped the taillights to the bumper so it'd be driveable in the meantime. Boy did it have some whacky behavior until I added a ground! It was finding paths that I would not have guessed. I recall sanding the frame a bit, stripping a long length of wire, and twisting it around the frame so as to get a ground. Worked for a few years, even after I added the bed back on.

 

[Marcozi]

Definitely sounds like a grounding issue.

 

[84gmcsierra]

I got the issue fixed yesterday. I have male and female connectors on the wires, so when I take the bed off to fix the front panel I can just disconnect the lights. I replaced those, but found out it was the new 1157 bulb that was the problem. I found an old one, put it in the socket, as well as pulled the contact points in the socket up a little, and the problem is solved. Hazards, blinker, and lights all function normally again. Thanks to all of your suggestions and help.