Erratic Electronics Behavior In '99 Sierra 1500

[Lv1G6He3V2]

Symptoms:

 

- An odd buzzing noise can be heard sometimes. It emanates from the dash. This is definitely an electrical noise; it's like when those old flourescant lights would start up, or when the power dips during a thunderstorm.

 

- Power windows stopped working. They would only go up or down 1" from lowest position and various clicking noises could be heard. Then they started working perfectly again when I had a mechanic looking at them. (Don't you just hate that?)

 

- Radio causes the aforementioned electrical buzzing noise for several seconds before/during/after using radio controls. It often happens when the radio is switched off.

 

- Gear lights (above/behind steering wheel) flicker, dim, or go out entirely at various times. Starting and activating the A/C before reversing out of a parking space, the gear indicator went out entirely.

 

- Turning on the front lights switches off many indicators on dash. The clock also goes out. No idea why.

 

- The clock goes out unexpectedly.

 

The truck appears to work fine except for these electrical oddities.

 

Suggestions? I don't want to sic the local mechanic on the ghost in the machine until I'm sure what's causing it to go nuts.

[OKLAGMCRUISER]

check all grounds on big 3. check loose battery connection or dirty battery terminals. gm batteries are easily stripped out...looks connected, but indeed is not. try these for starters...

[Lv1G6He3V2]

check all grounds on big 3. check loose battery connection or dirty battery terminals. gm batteries are easily stripped out...looks connected, but indeed is not. try these for starters...

 

We cleaned the battery and checked the terminals, so it's not grease/corrosion. From what I've read, the big 3 are the 3 power cables linking the battery, alternator, engine, and frame. I'm a little leery about that stuff so I'm going to take it to a local GMC dealer and have them work on it one step at a time.

[Lv1G6He3V2]

You can mark this [solved] if you want.

 

A broken fog light caused all the electronic problems. The fog light seal was broken just enough that water accumulated - lamp was 1/3 full of water - and bulb was broken, leaving the broken filament to dip in and out of the water depending on how level the vehicle was and whether it was moving.

 

Once the fog lamp assembly was replaced, everything started working flawlessly.