Brake lights flashing in extreme cold

Edit: The issue appears to have been related to the LED bulbs. I replaced the LED bulbs with incandescent and the issue appears to be resolved (cannot yet say with certainty). The Meso harnes works with incandescent bulbs and the switchback reverse/blinker LED has not given me any issue. Post 67 has video of it.

Update: So, after cold soaking overnight the break lights on my truck are flashing. I first noticed it at -6 F, however it is significantly worse at -38 F.

This is without me toyching the truck since the night before. No dash lights. No other issues. Still runs, and flashing stops as the truck warms up (but not until it warms up, turning it on does not change anything).

Tried disconnecting the brake light switch, but other than making it to were depressing the brake pedal did not turn on the lights, this did not change the flashing.

I'm thinking replace the relay. From what I can find, a frozen relay normally results in a circuit that will not close as ice is an insulator. So I'm not certain the relay is the issue as the problem is an inappropriately closing circuit. However, not being very knowledgeable with electronics, it feels like a good place to start.

Unfortunately, I will not be able to get a relay until tomorrow is I'm an hour or so away from any autoparts stores.

Original:

This morning my brake lights are randomly flashing with the truck turned off in the driveway. It is more of a flicker as the lights don't come on enough to fully illuminate the housing. There is no predictable pattern, sometimes the flashes will be in rapid succession, and sometimes there will be a minute or two between flashes.

I tried turning the ignition to the on position. Tried pushing the break peddle. Taking it out and putting it back in gear. Guess I should crank it. Not a fan of turning it on in the cold of I'm not going to Warm it up (-6 F/-21 C) this morning.

 

It is doing it while idling as well. No dash lights, no message. Acting normal on a short drive.

 

Brake...

Pull up on the brake pedal. Maybe it's not returning all the way.

 

Battery is pretty new and the headlights are fine. The brake lights are flickering on for no apparent reason. They light up fine when the break is pressed.

In the cold, my brake fluid is a smidge low (edit, no, it was below a sharpie mark from the factory, but at the 'max' line molded into the reservoir) and as the truck idles warm the frequency of the flickering is decreasing. So my current gues is something with low brake fluid and as it expands the issue is resolving.

If I did not have LED brake lights I don't think I would have noticed as the flicker dose not look to be long enough to light up the stock bulbs.

 

Thanks, fixed the spelling.

Tried pulling up on the peddle, no change and no notable movement.

 

My tag lights were flickering. Replacing the bulbs or lights should fix the issue

 

Bulbs are brand new. Plus this is a flicker on when they should be off. No flickering when appropriately turned on.

 

What did you replace them with?

 

New bulbs? I would start there!

 

MESO total tail stage 1. Though they were replaced a few weeks ago. Plus it is impossible for a bulb to draw power on its own. The flashing on is only a symptom of something else temporarily energizing the circuit.

 

Test the body harness to the light fixture with a DVM.

 

Brake switch...

 

Well, bringing it up to operating temperature appears to have solved it for now. Question is, does it come back?

 

It will, as nothing has changed hardware wise.

 

I have my parking and blindspot monitor sensors disconnected. Last year the BSM ones in the mirror would randomly flicker and not at full strength. Took a look and I had them bagged and ziptied but some road junk had gotten under including some moisture and salt. Cleaned it out with rubbing alcohol and then rebagged them. No issues since.

 

I'm guessing moisture and ice bridging in the cold somewhere exposed to engine heat or in the cab. With luck, it was a one time fluke. Though I may be sitting on a nest of electrical gremlins.

 

If it's ground switched circuit then any grounding after the lamp will complete the circuit and lights will come on. Shotty wiring, poor install, chafing, etc could be the cause. In any case, it's probably worth pulling the light assemblies and inspecting.

There goes that theory! - See below

 

It's not...

 

Awesome, gives me a place to start looking if it happens again.

 

Well, at -38 the break lights are flashing at a rate of about twice per second. This is while turned off after sitting overnight. I'm going to try replacing the relay once I'm back in an area with an autoparts store.

The frequency of flashing appears to be inversely related to the temperature, with more flashing the colder it gets.

This includes the break light on the cab (which, wgich still has the factory bulb.