A/C fan runs none stop 87 IROC - Third Generation F-Body Message Boards

aretha · 08-31-2009, 03:39 AM

I have an1987 350 iroc tpi and recently got a second hand ecm and eprom out of a 1988 same car and ecm +prom P4 12227165 eprom27C128.the car ran a bit sluggish so I took it all out put my 87 ecm back in with the 1988 eprom, what a differance in power good gear shifts and a louder engine note,I wonder if the 88 eprom had been modified?.The only problem I have is that the A/C fan feeps running all the time.my car had the stock fan switch in that cut in at about 220 or 30 and the drivers side fan was being used, since I put the jet switch in the fan cuts in at 200 the system has changed fans now the A/C fan runs.I have deleted the A/C and cold start injector a year ago.so as I was saying since my ecm eprom change my fan runs full time.Any ideas Guys would be help full.

DJP87Z28 · 08-31-2009, 08:57 AM

Yes, since you messed with the fan switches the ECM dosen't know what to do.

Stock fan set is controled by the ECM.

deadbird · 09-01-2009, 08:57 PM

For 87, if you removed the fan pressure switch (deleted a/c and all related lines) the blue wire needs to be grounded to prevent the ECM from seeing a fan request input. If the plug is still there and wiring in contact, a jumper in the plug will work just fine.
The fan pressure switch is/was located on the aluminum tube that is/was mounted on the pass side frame rail.

aretha · 09-03-2009, 02:38 AM

Thank's Deadbird I will try that, it sounds like a good plan. God above wasn't much help at all all though he has all the power.