My 90 IROC (305) cooling fans seem to be working ok. The 1st fan (Drivers side) comes on at about 230 or so degrees. The second one has not come on that I know of...(I haven't run the AC) I keep this car up at the mountain home and there is a road that is extremely steep, The signs say to turn off your AC at the bottom of the hill, and it also has turnout areas with 1 gallon jugs of water for overheating. I first went up this grade with the camaro and the temp went up from 190 to 230 before the fan kicked on and started to cool down, (I assume)...This is when the outside temp was only about 60 degrees...I started the car the next morning and watched the temp climb after 5 min or so and then at around 230 degrees the first one started so I think it is working correctly. My question is that if I add a summit stand alone adjustible stat on the second fan and set it for say 195 will it keep my AC from working? In the summer months it gets to about 110 degreess outside so I need to have a cooling fan start sooner then the factory settings... I looked at the wiring diagram and it dosen't seem to have an interlock with the compressor, so If I cut the wires going to the fan an install the kit; http://www.summitracing.com/parts/PRF-30104/ will this work ok? Will the compressor keep running? I don't see why it wouldn't. The second fan will then come on at 195 and keep running until it cools down or I shut the car off...What do you guys think? thanks Mike

Stock secondary fan turns on at 238° via the fan switch in the passenger head.
Replace it with AC Delco D1855B (or equivalent) fan switch. 215°F turn on. 5° cooler then the ECM switched primary. No splicing or, putting those horrid scoth locks on the wiring.

Any further details can be found using seach or, looking through a few recent pages, as cooling fan ?'s are frequently asked.

I agree with Deadbird. A simple fan switch will do the trick. And it prevents splicing, hacking, etc. It will have no effect on your A/C.

I run a 200/185° fan switch. Seems to work great for summer heat waves as well as cooler winter days.

How fast are you driving up those mountain hills? Keep in mind that anything over 40 mph and the fans will shut off automatically. At that point you're relaying on your radiator and air dam.