Here's the deal on my '93 LT1...the primary cooling fan works as it should. #1 fan comes on when A/C is turned on... or with A/C off, the fan comes on when coolant temp is about 227 degrees...cycles off when temp drops to 221 degrees.But the secondary fan will not come on either when A/C is turned on, or when coolant temp gets over 236 degrees.My actron scanner lets me cycle both fans on & off, so I know the secondary fan motor & relay are good.I also switched relays just to be sure, to no effect.With motor running and A/C on, the primary fan is on...but when I unplug it (it stops,of course) & then immediately plug it back in, the secondary fan then comes on and runs until the A/C is turned off...then the secondary fan will not come on again as it should.Any ideas on this? Thanks in advance.

 

could be a failing tune or chip. check your ecm to see if you have a chip added to the memcal.
this is the ecm, its in the engine compartment on the passenger side between the firewall and the fender well. take that grey cover off and memcal can be accessed



this is a memcal with a chip tune from solomon hooked to it. memcal is the blue and brown part. if you have a chip it will be between the memcal and the ecm like the green chip is.

 

Thanks for the fast help,Craby...my daughter now drives this car and I try to fix my kid's stuff as soon as I can (I'll drive my own broken stuff around forever and complain about it non-stop the whole time...drives my wife nuts)...the ECM is stock...I don't know enough the "fan switch" located on the driver's side of motor that my Haynes manual talks about...does this sensor/switch only control the 2 fan, or both fans? #1 fan works normally. #2 only comes on with my scan tool, or when I pull the plug on #1 fan...

 

the way you have tested it can only be a couple things. one being the coolant temp sensor found at the front of the water pump. we have two one there and one in the head by the #1 spark plug thats for the temp gauge. or the problem is in the computer system. i have seen guys chase this to the point of adding a toggle switch to turn the fan on. for some reason i thought the 93 had both fans coming on the same time on one relay. i think its the one speed for 93-94 that got me crossed. be a good idea to download the factory shop/service manual. brb

 

go here and click 93 firebird it should be the same as z28
http://www.mediafire.com/?40mfgeoe4ctti

 

From Shbox:

"1993- early 1994 - Primary and Secondary fans operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed. These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood."

Primary at 226 degrees F, Seconday at 235 degrees F

 

Hey Craby, thanks for the manual download...lotta good stuff in there...and Shbox. thanks for the info...a couple questions I have: once A/C head pressure is up, do both fans stay on all the time, or is the secondary fan still temp sensitive (the primary fan comes on as soon as the A/C is turned on... with A/C off #1 fan comes on at about 227 degrees). After all the years I've owned this car I thought that both fans stayed on as long as the A/C was on...now I'm not sure if that was the case... If I jumper the two contacts on the coolant switch on the water pump, will both fans come on...will this damage the ECM? Is this a simple man's way to keep both fans on all the time, or would this not work?

 

4th Gen LT1 F-body Tech Articles

That is a good read from Shbox and should answer most of your questions.

Not sure why would want to run both or one fan constantely. It would impede cooling at highway speeds and require more time for the computer to enter closed loop mode. It would also increase wear on the engine has it would now take longer to get the engine to operating temp.

 

have you tested the engine temp sensor.

 

I was just thinking to get the fans going temporarily all the time so the car is safe to drive until I can figure this thing out...Not a good idea I see, now that the manual shows more stuff hooked up to that sensor than just the fans...I am checking the coolant temp sensor circuit, and the A/C head pressure as I speak...