Thanks for those individuals who helped me trouble shoot why my Vette is running alittle hot. There are 2 fans on my 1990 L98. The top fan comes on some where around 245 degrees my estimate. The bottom fan never comes on at all. So it appears one fan is not working and the other fan is not coming on like it should ( 228 degrees ). Any suggetion on how to adjust the working fan to come on sooner? The bottom fan does not work. Wiring looks okay going to it. Do you think the 2nd fan motor is shot? Any help moving forward now that I have discovered the problem is appreciated. Just a note, the one fan ( working ) does come on eventually and does cool the car back down to 225 degrees then it shuts off.

 

Do you have the digital gauges on your '90 model?? It really sounds like your gauge is reading higher than actual temperatures.

 

Its not the digital. Its starts at 100 and the next read is 260. You think the gauge is not agreeing with the actual temp??

 

Later C4s have analog gauges and a gauge button for digital readouts.
The digital being more accurate. I don't know if the 90 models have that feature, but if you do I would check the analog against the digital gauges. It would be a little risky to drive and overheat based on the presumption that the gauge was wrong, but I would want to check the gauge accuracy. The fact that the main fan turned on at 245*F causes me to question the accuracy of the gauge.

 

Turn on your AC as a quick check for the second fan, they should both kick in with the AC running.

 

Aminnich and JRZVette,

Thanks for the information. I will try the A/C in the morning and see if both fans kick on. Thankgoodness for this forum and folks like you both.

 

Just a thought:

My '88s main fan is regulated by a relay. The relay located on the driver's side wheel well in the engine bay. If it's disconnected or faulty, the main fan won't work.

click Eckler's link:
Corvette Engine Cooling Fan Relay, 1988-1994

 

On the 90's the actual temp and the gauge are way different from each other. The gauge is not a linear read out, so ya can't tell exactly what the temp is. The fan "call" temps are programed into the EPROM. The FSM gives the exact temps for Fan 1 and fan 2, the program has on & off temps for both fans.

When the A/C is activated the both fans come on if the temp is over a programed point. You can test two things at once here if you let the car go to closed loop temp on the coolant @ idle. One fan should run at 228, if the temp gets above that the other fan will come on to help, and fan 2 will shut down once the temp goes below a set temp. This tells you if both fans work and if both relays work. Next, while still at closed loop temps, turn on the A/C and see if both fans come on. If they do then watch to see that as the temp goes down that fan 2 may turn off if the temp goes below it's call in temp. If all of that checks out then everything is working properly. Ya need to look in the FSM for the pre-programed temps, as I'm just using numbers...I don't remember the real numbers for all this stuff. The fan programing may be a bit different for a L98 than my LT5 but the idea of how the fans are used is the same...the call temps may be different for the L98.

As an aside, on my temp gauge...all the action seems to happen when the needle gets to the last 1/4" right before the 260 mark. Fan one comes on & runs and the temp drops a bit and it goes off. If the temp goes past the last 1/4" of the sweep both fans are on till the needle gets jsut a bit beyond the 1/2 way point and then Fan 2 shuts back off. Like I said mine is an LT5 but I still think the program is the same for a L98....but you see what chevy had in mind for the fan program.
Sorry to be so long winded!:o


Tom
Sorry, forgot this, there is a way to use the climate control LCD to give you the temps the ECM is seeing, in degrees C. I just keep forgetting how to do it!