Electronic Speedo Dims when brakes applied and flashes with left turn signal--HELP

Tonight, when my family and I were on the way back home from yet another night out in the wagon, trouble struck. When I put my left turn signal on, the digital speedo blinks out of sync with the signal--the speedo goes dim each time the pretty green left arrow lights up. There is no issue using the right turn signal. When the brakes are applied, the speedo goes dim, unless the left turn signal is on. The left turn signal's ability to make the speedo blink overrules the brake pedal's ability to dim the speedo.

When the headlights are turned on, the situation changes. When the headlights are on, the speedo will not dim; however, the left turn signal no longer works--it stays on without flashing (both the indicator and the actual signal lamp) when engaged. I checked the fuses at the left end of the dash and found no issues. Could it be the turn signal flasher relay? If so, where do I find that relay on the vehicle? If not, what could be causing my problem? Any help you can provide will be appreciated.

Update. I just walked around the car in the dark. When the left turn signal is on, the right turn signal lamps and the license plate lamp also flash (although not as brightly as the left side)...as mentioned before, the left turn signal can only be activated when the headlights are off. When the headlights are off, the hazard flashers are extremely dim. I also noticed that the lamp behind the front right amber "cornering lens" is not illuminating. The "corner" portion of the left headlight is, however, well lit when the headlights are on. There are other Chevy owners that have complained of similar issues, but I have not seen a solid solution yet. One guy "pulled on the wires under the dash" and everything started working again...not very helpful.

I would guess you may have a grounding issue. That is one thing that can make your lights act quite weird.

I would second that. The turn signal is probably grounding through the dash, and other lights. Check the grounds at the bottom of the A pillar. You have to remove the DS door sill, and they are behind the kick panel under/behind the hood release.

I have play practice at the church this morning but I will get on it this afternoon and let you know what I find. Thank you for the help. I will also check the grounds to the left rear taillight assembly (should be easy to find). Any other areas to check?

1st thing I would check on a 94 is the Aux Batt post.

jasonlachapelle wrote:

1st thing I would check on a 94 is the Aux Batt post.

Bingo!

Tom C.

Okay. Loosened and tightened the grounds toward front of floor under driver's door sill. Tightened ground for right rear light assembly. Took nuts off aux battery post (which is brass). Cleaned it up, although it didn't need it and tightened everything back down. Still same problems. What else can I try?

There should be three wires grounded behind the coil. Check those.

Tim, thanks for the additional idea. Same routine as others--nuts off, clean, reassemble, tighten. No change.

The turn signal switch could have an internal short, or a wire could be bare. You are going to have to chase the voltage with a VOM.

Update. On the way to church this morning, I continued to have the same issue. On the way home and for the rest of the afternoon (so far) there have been no weird dash issues. The only issue right now is that the rear left turn signal bulb is not flashing when the turn signal is on--tail lights and brake lights work fine. Before--when all the crazy stuff was happening--the turn signal bulb worked fine. Could I have a bad socket? My tail gate gets opened and closed a lot because my kids and their friends love to sit back there. Maybe I should change the bulb and socket. Could that cause my problems?

Thanks for the help, everybody. I pulled the upper two bulbs in the rear left and they were black (they were working before, so I must have done something with my mucking around). I changed both bulbs out and the turn signals started working, but the brake lights did not. I squeezed the scotch block connectors and unplugged--and plugged back in--the bundle of wires that goes to the taillight assembly. Everything works fine now. We will see if it lasts past the first bump or pothole I hit. Again, thank you for the help.