Turn signal mystery

[BattleCruiser]

I have a bizarre turn signal issue that is so illogical I do not even know where to start.

With my lights off both turn signals work normally from the outside. However, when I use my left turn signal, again, with my lights off, the dash lights flash also.

With lights on, my right turn signal works normally. My left turn signal, however, flashes all four blinkers. That is the problem. Here are surrounding conditions.

The left arrow on the instrument cluster has never illuminated, since I've had the truck, which is about 4 1/2 years, although the blinking function has always worked, until this recent issue.
Both tail lights have been replaced (new, this week). All exterior bulbs working.
In very cold weather, my left turn signal will go on, but not blink. I have to touch the stick manually to make it blink, which actually does not work, because as I said, all fours blink if lights are on. The absence of auto blinking is intermittent, but seems to occur in cold weather.

With lights off, pressing the brake pedal illuminates the instrument cluster.

I think that's about it. This all started about 3 weeks ago. I only found out that all fours were blinking when I manually work the left blinker because I got pulled over by a State Trooper who told me every time is use my left turn signal my right blinks also. I work on this truck a lot and it is in good condition. Great condition actually. But I do not even know where to start on this one.

And clues appreciated. Thank you.

Mark

[shorod]

My first thought is that you have a grounding issue for the turn signals somewhere which could explain why the instrument cluster lights flash - the turn signals are getting their ground through those bulbs. The first place I'd check in this type of scenario would be for aftermarket trailer wiring, and if installed, confirm whether or not all connections were made with solder and adhesive lined shrink sleeving. If not, there's a good chance corrosion has set in and several feet of wiring will need to be replaced in order to get good, solderable wire.

You don't mention what year your Silverado is so I'm not able to look up wiring diagrams to see if there is a logical explanation for the left side to act up but not the right side.

-Rod

[BattleCruiser]

Rod, that is excellent information. 1995 Silverado. 2WD, 350. I am heading out on my hitch for two weeks so I won't be able to get into this for awhile, but I will let you know.

Thank you,

Mark