cooling fans not kicking on at temp. looking for input

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

cali+Mocasho+

89 white 3.2 145k
Joined
Sep 5, 2015
Messages
219
Reaction score
36
Location
califorina
I have a 90 mtx i bought not that long ago and seems the cooling fans will not kick on when it gets hot.
Also fans will not kick on with max ac button. (ac dosnt work was told the clutch burned out)
When doing KOEO test fans come on.
I went to replace the temp sensor and cracked the housing for it. I have another housing to install with new sensors just have not done it yet.
My question is. if the fans come on with the KOEO test would that confirm the ccrm is good?
If the temp sender dosnt fix remedy the issue should i suspect the ecu? it currently has the LOS ecu dont have a spare so i cant swap it out nor the ccrm.

All input greatly appreciated thanks
pics for attention...
 

Attachments

  • 0ks4yvbp.png
    0ks4yvbp.png
    2.1 MB · Views: 8
  • qdy2yl7e.png
    qdy2yl7e.png
    2.7 MB · Views: 9
  • 8wnv6f7a.png
    8wnv6f7a.png
    2.1 MB · Views: 9

rubydist

SHO Master
Staff member
Super Moderators
Joined
Jun 25, 2007
Messages
7,481
Reaction score
3,332
Location
Denver
Do they run at both speeds during the test?
 

SHOrod

Torrie Tuned
Joined
Jan 1, 2006
Messages
1,065
Reaction score
409
Location
Cedar Rapids, IA
That's a beautiful color on your SHO! On the 1990 there's a dropping resistor for the fan. As mentioned above, if you only noticed one speed, I'd suggest checking for an open fan dropping resistor. All the control for the radiator cooling fan is through the CCRM and the PCM controls the fan based on engine temperature as well as for the self test, so I'd not be inclined to suspect an issue with the PCM yet since it does activate the fan for the self test.

The dropping resistor should be in series with the White/Red wire at pin 10 of the CCRM connector and be located on the left (passengers) side of the engine with a Black/Orange wire on one end and a White/Red wire on the other end.

Also, be aware that there may be two coolant temp sensors on your car. I haven't dug into the wiring diagrams for it, but around that time Ford would often use a temp sensor for the PCM to turn the radiator fan on and off and a separate sender/sensor for the light/gauge in the dash."

-Rod
 

FastCAD

SHO Member
Joined
Feb 22, 2015
Messages
299
Reaction score
128
Location
Miami, Florida
I have a 90 mtx i bought not that long ago and seems the cooling fans will not kick on when it gets hot.
Also fans will not kick on with max ac button. (ac dosnt work was told the clutch burned out)
When doing KOEO test fans come on.
I went to replace the temp sensor and cracked the housing for it. I have another housing to install with new sensors just have not done it yet.
My question is. if the fans come on with the KOEO test would that confirm the ccrm is good?
If the temp sender dosnt fix remedy the issue should i suspect the ecu? it currently has the LOS ecu dont have a spare so i cant swap it out nor the ccrm.

All input greatly appreciated thanks
pics for attention...
the temp sensor next to the thermostat is for the dash (one wire). the second temp sensor (which is the culprit) feeds the pcm. this sensor is at the back corner of the block (drv. side) facing the firewall & speedo cable (lower). (two or three wire??).
p.s. the muliti wire connector u may find back there (loose) is california only.
best to ya.
 

BaySHO Performance

SHO Member
Joined
Feb 25, 2001
Messages
789
Reaction score
603
Location
SF South Bay
Probably a bad ECT sender. Everything else should be fine as the fan works on the self test. But I put a new Durarast SU201 in this car in 2019, So it may be a bad circuit or ECU.

IMG 20190616 151633223 HDR 1024x445
 

Greg Corcoran

SHO Member
Joined
May 23, 2016
Messages
153
Reaction score
59
Location
Denver metro area
The ECT sensor (the one described as in the back corner of the block, actually in a heater hose line fitting for my '95) was the culprit in my case. It apparently drifted low maybe 30 - 40 degrees, but did not fail, so no codes were set. The car never thought it was hot even though the gauge on the dash (from a different sensor) showed alarmingly high needle. The trick to confirm this sensor is off is to disconnect the ECT sensor with the engine running and the fans will come on. Replaced the sensor and fans worked as they should. The trick was taught to me by a retired Ford dealership mechanic.
 

BaySHO Performance

SHO Member
Joined
Feb 25, 2001
Messages
789
Reaction score
603
Location
SF South Bay
The ECT sensor (the one described as in the back corner of the block, actually in a heater hose line fitting for my '95) was the culprit in my case. It apparently drifted low maybe 30 - 40 degrees, but did not fail, so no codes were set. The car never thought it was hot even though the gauge on the dash (from a different sensor) showed alarmingly high needle. The trick to confirm this sensor is off is to disconnect the ECT sensor with the engine running and the fans will come on. Replaced the sensor and fans worked as they should. The trick was taught to me by a retired Ford dealership mechanic.
The ECT is in a water housing bolted to the rear cylinder head. The one in the heater tube is the CELO (Cold Engine LOckout) switch to stop the climate control fan from coming on while the engine is cold. Not the engine cooing fan.
 

Greg Corcoran

SHO Member
Joined
May 23, 2016
Messages
153
Reaction score
59
Location
Denver metro area
The ECT is in a water housing bolted to the rear cylinder head. The one in the heater tube is the CELO (Cold Engine LOckout) switch to stop the climate control fan from coming on while the engine is cold. Not the engine cooing fan.
Thanks for the clarification - I may have confused the two. I know I have a defunct CELO switch too, but was unable to find a replacement when I was replacing the ECT several years ago.
 

WinsletshawnA

New Member
Joined
Aug 9, 2021
Messages
7
Reaction score
1
Location
Tampa, FL
Hey @cali+Mocasho+, it sounds like you're on the right track with the temp sensors. Since the fans work during the KOEO test, the CCRM is likely fine. Replacing the temp sensor might solve your issue, but if it doesn't, I'd next check the ECT sensor, as others have mentioned. The ECT sensor can often be the culprit in cases like this. Good luck with the fix, and keep us posted on how it goes!
 
Back
Top