My '92 L98 refused to run either of it's fans today. I followed the trouble shooting in the service manual to no avail. Grounding the ADLC, grounding the ECM lead to the relays, voltage checks off the relays and at the fans. Everything checks OK, I jumpered the fans and they run. The temp gauge works. It has used the Hyperchip and 180 thermostat for over a year and never got close to hot. Does the temp sensor feed the gauge and the ECM? If the temp sensor is bad (not telling the ECM what the temp is to start the fans) will the gauge still read properly? Any suggestions?

 

you should have a seperate temp sensor just for the fans in the head on the passanger side.. also try checking your fan relays after youve made sure the sensor is ok,, if all else falls do what i did wire both fans to a manual switch(unless your still running your air conditioning) one of the best things i ever did for my car i can get the temp below 180 when idiling its great

 

the temperature sensor on the intake manifold feeds the ecm only, the temp sending unit on the drivers side head feeds the guage, and like i said the fan sensor is in the passanger side head. i just went thru all this myself 2 days ago.

 

do you have a/c? if you do are the fans working with it turned on?

Lordmetal... its a fan switch on the passenger side.

You guys know alot of these cooling issues can be better traced with an ALDL cable, a laptop, and free diagnostic software right? I use Turnerpro RT, and Datamaster. I can easily see what the computer is seeing as far as temperature goes, that way i know if the fans even SHOULD be on.

 

fan switch fan sensor u get my point

 

http://www.thirdgen.org/techboard/co...-diagrams.html

Is that what you were using to troubleshoot your fans? I would encourage ALL 3rd gen owners to download those pictures in the link above. It's a gold mine of information regarding fan diagnosis.

Do you have the stock fan switch in the passenger head between the #6 and #8 spark plug? They don't turn on until the coolant temp is at 235°F or more....In my own experience, I used to wonder if my passenger fan was working or not. But it turns out that the car just wasn't getting hot enough for it to come on. Putting in a 200/185 fan switch made me realize that the fan actually was working as well as give the added benefit of keeping the car cooler, but not too cold.

If you're referring to the Hypertech Thermomaster chip, that turns the driver side fan on at 176°F. Off at 166° (aka it will never shut off, because how often are you at 165° or colder while driving slower than 40 mph)

 

Turning on the A/C will turn on the driver fan immediately and will turn on the passenger fan when the high pressure side of the A/C gets past 233 psi. Most of the time this means the passenger fan will turn on pretty much immediately....BUT If your A/C is a little bit low on charge, the passenger fan won't turn on.

I had this experience myself when I was low on R-12. Passenger side would never turn on. I had 1.9 lbs of R-12 in the system when the regular amount was supposed to be 2.25 lbs. Air conditioning still cooled so so. Only got down to about 50°F duct temps. But the compressor would cycle way too much. Once I had the proper amount of refrigerant in there, the passenger fan started up immediately upon turning on the A/C.

 

Hey gang,
I replaced the coolant switch and it still will not run the fans. They will not come on with the AC on either. The thermostat is open and the water pump moves the water.
Gord's Green Z28 - yes it's the Hypertech chip with the lower thermostat and replacement secondary fan switch on the right side. I don't have access to a laptop to diagonose the ECM but grounding the ECM lead to the relays should bring them on - but it doesn't. Unless anybody has more ideas; it's headed for my nearby shop. Thanks for all the info and advice.

 

The junction by the battery that feeds the fan relays had partial melting and needed a new terminal connector. Plus the fan relay connectors needed new terminals. Holding them just in the right position would allow the fans to run; but when mounted on the firewall they would shut off until I put new terminals into the relay socket. All is well - Thanks

 

On my 88 Iroc I connected a switch between the wire going to what is called the heavy duty coolant switch and ground (I had broken the connector during removal of the headers).
I put the switch on the dash under the steering wheel. I am running stock temperatures to help pass Ca. smog but I can avoid high temps with the passenger side fan. Simple and it works.

 

hey jon@aol. where did u find new terminals for that.. mine did the exact same thing. i just wired both fans to one switch and manually operate them now