Not sure what is going on here. I have the stock single fan set up in my '91Z. All electircal lines have good ground. I just replaced my third relay in the last three months. I do have an inline manual on/off switch that is wired under the dash, but it has been there for many years and has opereated with no fault. Last realy I got was from the dealer, OEM but made in China? (this is what I got from the dealer - part # 14089936) Car is a weekend warrior, and as such this relay has less than 50miles on it. When first installed it operated properly
I disconnect my battery when not driving the car, and am wondering if I am shorting anything out while pulling or reinstalling the bat negative terminal? I have done this for years with no problems.
I'm not sure where to look next - or am I getting faulty relay's?
Is there a way to test a relay at home?
TIA
-Andrew

 

To test a relay (for this example I will assume a NO relay) apply 12Vs to the primary terminals (input) and then measure the resistance on secondary (output) terminals. The output terminals should read close to 0 ohms with 12Vs applied and infinite resistance with the 12V removed.

 

I was cookiing relays left and right on my 87.........so I stopped buying them from NAPA, then i bought them from the dealer..........this worked fine. then i saw a thread on here where somebody noted that their old fans were " drawing allot of amps"...........this got me thinking.......when I jumped my relays to see if the fans would run it really let out a good spark as the fans started up...........so just to be safe, I bought two new fan motors from TPI parts.........I haven't blown any more relays.........but i guess I can't say for sure if it was just the change to GM relays.......

 

could be an issue with the fan motor. make sure it isn't binding and turns smoothly.