Cooling fans

[rfried20]

Howdy,
I’ve had a very productive last two weeks. New fuel tank, pump, and filter had the car start and running for the first time in over 20 years. New radiator hoses and thermostat, new tires. What I’m needing help with is the cooling fans. I’ve never heard or seen them come on. Any ideas on how I check if they’re good and if they are can I run a manual switch for them. I don’t want overheating, obviously

Thanks for the help. I am so beyond ready to take this thing cruising!

 

[Irish Pride]

The cooling fans are powered by the CCRM mounted on the upper radiator support. Run 12 volts directly to the fans and verify that they will run with power. If not, replace the motors. If so, you either need to look into the CCRM or the coolant sensor mounted on the rear water outlet on the rear head. You might have a stuck relay in the CCRM and a few good whacks with the plastic handle of a large screwdriver can sometimes free it up. If not the CCRM then it might not be getting signal from the rear sensor. There are two coolant sensors. The one on the front head is for gauges. The one on the rear head is for cooling fans. I've never actually seen this sensor go bad so its unlikely the problem but maybe its unplugged. I have seen that happen.

-Chad

 

[ScotSHO]

Additionally, it's important to know when the fans should turn on. If you have the A/C running (EATC is in AUTO, MAX A/C, DEF, DEF/FLR or FLR/PNL) then one fan should turn on and run constantly. If the coolant sensor sees the temps are above a certain point (215, 220F?) then both of the fans will turn on.

Also I think the fans turn on briefly during the EEC-IV self test: https://wiki.wikisho.com/wiki/EEC_Self_Test_Procedure

 

[rubydist]

The fans also turn on as part of either the koer or koeo test (don't recall which any more). That is the best way to test because that tells you if all of the control and power side stuff works. Then the only thing that is left is whether the coolant temp sensor works or not, and there will be a code if it doesn't.

 

[Devin]

On my 90 it's KOEO. Hear a bunch of clicking and the fan turns on for two seconds.

 

[Greg Corcoran]

<snip> Then the only thing that is left is whether the coolant temp sensor works or not, and there will be a code if it doesn't.

Actually mine "drifted" about 30 or more degrees low, so a fan wouldn't come on unless I turned on the AC. Mine has two fans. There was no code. Then the fan motor for the AC fan failed... took a long time to find the correct fans for a '95 MTX (one year only. MTX only, apparently?)

A bugger to diagnose. I never did. I worked around it for a year. Replaced the CCRM more than once. After that, Rigged a test signal to the CCRM from the ECU and fan worked, so Replaced the ECU. Still no fan. Wired up a bypass switch to trigger the CCRM, and had to watch the gauge until I found the new fan unit.

Dumb luck, I ran across a former Ford dealership mechanic from the 80s and 90s, so I told him my tale of woe. He reached down unplugged the coolant sensor and the fan kicked on. Looked at me and said "Bad ECT." I said it should be OK, no codes were ever set. He said in that case then ECT drifted low, but still passed self tests becuase it was sending a valid signal. He made it seem like this happened somewhat frequently when these were still being seen by dealerships.

 

[rfried20]

The fans also turn on as part of either the koer or koeo test (don't recall which any more). That is the best way to test because that tells you if all of the control and power side stuff works. Then the only thing that is left is whether the coolant temp sensor works or not, and there will be a code if it doesn't.