I have an 88 Iroc z 350. Anyway, the other day I had the Hayden fan turn-on relay (part no. 3652) put in my car by a mechanic. Now the car electrical system is acting funny. The two main symptoms are: when the car has not been running for more then a few minutes, if I turn my dash board lights on my tach, oil pressure gauge, and electrical gauge all go to 0. If I rev, my tach goes up and stays at the top of its range. If I dim the lights they act normally, and after about 5 mins of driving they act normally.
2nd symptom I am not sure is related. I have an after market sound system, and now the speakers go in and out depending on when i hit bumps. I imagine the two are unrelated, but on the off chance there is a correlation, (prolly just a loose wire in its case) I figured I'd mention it. Any help would be appreciated.

 

Sounds like a bad ground, or maybe moisture got into something.
It also sounds like a similar problem when the printed circuit board go's bad on the back of the gauge cluster. Sounds like maybe you got some moisture in there, and when the car heats up it evaporates and go's away. Thats a shot in the dark, but I would try there.
Again the speakers sound like a bad ground. Maybe when the relay was installed the mechanic knocked a ground wire loose. I would start looking for a bad ground also.