Ive been chasing a problem on friends 97Z28 for awhile now. The fan have never worked right sence he bought the car. The dont come on with temperatur but when you turn the defrost on it VERY slowly starts to turn. Sence then we have converted it to OBD1 and the problem remains. We have replaced the relays, fuses and I even pulled the working fan off my car and it did the same thing on his. Im at a lose here. Does anyone have an idea what would cause this? Thanks alot.

Jeremy

 

I'm at a bit of a loss, are you referring to the engine cooling fans or the blower motor for the A/C&heating system?

 

Oh, sorry. I guess I wasnt real clear on that was I? Im talking about the cooling fans on the radiator. The primary fan only works when the defrost or a/c is on. And the secondary fan never comes on.

 

If the fans work fine when you jumper power and ground directly to them, it sounds like a wiring problem between the relay panel and the fans. Also check the grounds on the radiator support.

 

Shoebox, Thanks for the tip. Im gonna head back to his house this evening and check out all the wireing and grounds. Thanks again for your help.

Jeremy

 

Shoebox, Im still having trouble with this. There is no resistance at any of the wires, but I dont know what is opperational or not sence the car is a 97 with OBD1 conversion. Doesnt the 97s have 3 fan speeds? It seems like the fan is stuck on the lowest speed possible. Would the OBD1 conversion effected the fans at all? Thanks for your help.

Jeremy

 

The fans are two speed, and the low speed is what you'll see most often. Even in low speed, both fans should always be turning if any are turning at all--one fan only, even on high speed, does a poor job of cooling. When/if you see high speed depends upon when that mode is programed to kick in.

BTW, the OBDI conversion won't affect things at all. The difference between early cars--one fan, then the next vs. both fans low speed, both fans high speed--was done with wiring, not programming. When the PCM tells "Fan 1" to come on, both will come on at low speed and "Fan 2" comming on kicks them both up to high speed.

 

Ohh ok I see. I didnt know what the real difference was between the OBD1 and OBD2 were sence OBD2 has 3 relays and all. Thanks for clearing that up. Im gonna check the colling fan switch and make sure it works then if thats not it Im gonna have to get my friend over to double check the programming. Thanks alot for the info.

Jeremy

P.S. Both fans are running but at very low speed. Thank car got to 230 degrees and the fans never kicked into high speed. I dont know if its the temp switch or the program. Im gonne figure it out soon. Thanks again.