ECM ground for primary fan
Thread Starter
Instructor
Joined: Feb 2004
Posts: 141
Likes: 4
From: Scottsdale AZ
ECM ground for primary fan
As I understand the service manual, ground should be provided at C1 of the ECM when calling for primary fan operation. I understand also that 12 VDC to pin B8 of the ECM will emulate the A/C being on which should then throw C1 to ground. This is a L98 in a 58 vette without A/C. Is this correct? Is another input needed to switch C1 to ground? Also should the primary fan sometimes run when the engine is up to temp and then shut down?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Fan cycles to maintain a temp of around 226 degrees. Should be off at cruise above 35 to 40 mph.
A/c input at B8 is for idle and WOT, compensating for compressor load at idle and knocking it off at WOT.
Input for a/c fan is at Pin D11. Grounded through a pressure sensitive switch which opens with high pressure, the ECM drives the fan when the switch is open. If it's not running to ground now, the fan should be running.
You might want to talk to the guys at Street and Performance - www.hotrodlane.cc - they put a lot of TPI's in different stuff and may have something that works better for your application.
A/c input at B8 is for idle and WOT, compensating for compressor load at idle and knocking it off at WOT.
Input for a/c fan is at Pin D11. Grounded through a pressure sensitive switch which opens with high pressure, the ECM drives the fan when the switch is open. If it's not running to ground now, the fan should be running.
You might want to talk to the guys at Street and Performance - www.hotrodlane.cc - they put a lot of TPI's in different stuff and may have something that works better for your application.
