1989 C-4 Cooling Fans
05-29-2017, 06:11 PM
#1
1989 C-4 Cooling Fans
Main fan was not working changed out relay all good. Now both main and auxiliary fan always running? I do not believe this is correct? Solution please?
05-29-2017, 09:28 PM
#2
Team Owner
Member Since: Dec 2012
Location: Outside the Quick Stop N.J.
Posts: 30,426
Received 1,596 Likes
on
1,074 Posts
The main fan is controlled by a coolant temp sensor (between cyl#1-3), it should come on @~225 deg, while the other comes on @ ~235 deg or whenever the A/C is on.
05-29-2017, 09:56 PM
#3
Pro
If you have an auxiliary pusher fan in front of the AC condenser it is controlled by coolant temp switch found between cylinders 1 & 3 in the drivers side cylinder head. It comes on @ ~238*F and off @220*F. The aux fan temp switch between cylinders 1 and 3 shorts to ground at 238 F! This grounds the aux fan relay coil and turns the aux fan on. The ECM turns the main fan on at 228 F and off at about 210 F. The main fan is turned on by the ECM based on inputs from the coolant temp sensor, vehicle speed sensor, and the A/C coolant fan switch.
Last edited by mako41; 05-29-2017 at 10:11 PM.
05-29-2017, 10:01 PM
#4
Pro
Are you the original owner?
The aux fan is controlled by a coolant temp sensor/switch found between cylinders 1 & 3 in drivers side head. Is it permanently grounded? You sure the aux. and main fan relays are good?
05-30-2017, 07:56 AM
#5
Replaced both relays new.
05-30-2017, 08:01 AM
#6
OP - it seems apparent that there's been a modification done to the fan wiring.
Do you have the FSM for your car? It should be easily enough researched.
Do you have the FSM for your car? It should be easily enough researched.
05-30-2017, 11:11 AM
#7
Team Owner
Member Since: Sep 2001
Location: Athens AL
Posts: 59,642
Received 1,400 Likes
on
1,016 Posts
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
No that's not correct for an '89. The main fan is controlled by the ECM it comes on when the coolant temp sensor hits ~228*F and off @ ~210*F. The Coolant Temp Sensor can be found below the thermostat housing.
If you have an auxiliary pusher fan in front of the AC condenser it is controlled by coolant temp switch found between cylinders 1 & 3 in the drivers side cylinder head. It comes on @ ~238*F and off @220*F. The aux fan temp switch between cylinders 1 and 3 shorts to ground at 238 F! This grounds the aux fan relay coil and turns the aux fan on. The ECM turns the main fan on at 228 F and off at about 210 F. The main fan is turned on by the ECM based on inputs from the coolant temp sensor, vehicle speed sensor, and the A/C coolant fan switch.
If you have an auxiliary pusher fan in front of the AC condenser it is controlled by coolant temp switch found between cylinders 1 & 3 in the drivers side cylinder head. It comes on @ ~238*F and off @220*F. The aux fan temp switch between cylinders 1 and 3 shorts to ground at 238 F! This grounds the aux fan relay coil and turns the aux fan on. The ECM turns the main fan on at 228 F and off at about 210 F. The main fan is turned on by the ECM based on inputs from the coolant temp sensor, vehicle speed sensor, and the A/C coolant fan switch.
It appears they have been both wired together and grounded all the time to make them run. This is actually detrimental to cooling once you get up to speed, and will eventually burn out the fan motors.