Cooling fans not turning on- 1990 legacy

[newsance]

Hello,

I'm finding neither cooling fan in my car is coming on. I've checked fuses and that both fans spin freely.

 

My best guess is that the coolant temp switch is bad, as the fans would be controlled by seperate relays, right?

 

Where is the switch? I coouldn't find one on the radiator.

[porcupine73]

Do any fans come on if you engage the a/c (if it has it)? How do you know the temp is hot enough for them to come on?

[newsance]

Do any fans come on if you engage the a/c (if it has it)? How do you know the temp is hot enough for them to come on?

 

No, they do not kick on with AC.

 

The temp on the gauge has been just under the redline with no fans. Believe me, its getting to the point that the fans should be kicking on.

[porcupine73]

Hm...okay, well if neither fan is even coming on with the A/C then I think you should maybe backtrack from the fans themselves. Do the fans work if you unplug their harness and power them directly like with (fused) jumper wires?

 

If that works, then may need a wiring diagram. Maybe the fan relays are bad, or there's a wiring issue, or the ground is bad, etc.

[heartless]

first off - unplug the fans from the harness and jump power to them to make sure thay are even functional - replacing a relay wont help if the fan motors are toast.

IF they are functional, then go to the next step of finding/replacing the relay(s) or whatever you are going to do.

[Legacy777]

This may help

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/coolingfanwiringdiag.jpg

[newsance]

This may help

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/coolingfanwiringdiag.jpg

Thanks. Are both fans driven off the same circuit here?

 

From what it looks like, I can probably rule out the temp sensor, as I would assume the ECU would be throwing a code if it wasn't getting a temp signal. If both fans are driven on the same circuit, that would leave the relay or wiring as the culprit. I'll check the fans, but I am 99% sure they are good as they spin freely, and bad bearings are usually what kills em, right?

[porcupine73]

Did you power the fans directly at the their connector to make sure they both work?

[Legacy777]

Thanks. Are both fans driven off the same circuit here?

 

From what it looks like, I can probably rule out the temp sensor, as I would assume the ECU would be throwing a code if it wasn't getting a temp signal. If both fans are driven on the same circuit, that would leave the relay or wiring as the culprit. I'll check the fans, but I am 99% sure they are good as they spin freely, and bad bearings are usually what kills em, right?

 

I believe there is also a sub fan relay. It's weird, some legacies have it wired up where both fans come on when the ECU tells it to, and others, only the man fan comes on when the ECU tells it to. However in that case, the sub fan comes on when the AC kicks in.

 

The coolant temp sensor is very weird....it can be bad, and not work right, and not get a code. I think when they fail their resistance stays within the "normal" range, and the ECU doesn't have the advance programming the OBD2 ECU's have where it times the coolant temp sensor, and if it doesn't change/warm up in a certain amount of time, it'll give a code.