Rad fan always on when power on - Toyota Nation Forum : Toyota Car and Truck Forums

freakinbox · 03-11-2009, 11:57 PM

Ok now on my car the rad fan and the ac fan always run together. Problem is normally they only do so when the car heats up. Both fans run all the time the moment I turn the key to the on position.

I have tried replacing both sensors in the thermostat housing with no luck. I have considered replacing the relay. What I am wondering is if the fan has gone bad or wires to the fan may have gone bad and toyota has a fail safe that just causes it to run forever.

I know this problem came up a few times and I followed a couple of the threads with no answers comming up. At this point I am wondering if the people who have had this problem have figured out what it was and maybe give me ideas on where else to look.

erixon · 03-12-2009, 07:44 AM

it sounds like it might be a relay. I had a crx that had a screwy relay, and it was on all the time.

blb · 03-12-2009, 08:50 AM

Is your A/C system discharged? Seems I had a '91 that did this until I recharged the A/C, and after that the fans worked normally.

Also, I know that if the wires going to the temperature sensors loose continuity (disconnected, loose connection or broken wire) this is a fail safe design that will cause the fans to run antime the ingition is on in that event.

freakinbox · 03-12-2009, 05:06 PM

yeah the a/c doesn't work.

I also have been thinking of running some new wires to the temp sensor.

***SCT*** · 03-12-2009, 08:37 PM

This could be a longshot...

With my '96 Taurus GL wagon, the fan stayed on even without the key (the key doesn't disconnect constant power like the Corolla, whereas the 12V outlet is always powered but the ae92 12v isn't unless the key is on ACC at least). It was the ECU that caused the fan to stay running until the battery was sucked dry.

Maybe it could be the ECU, if all else fails.

freakinbox · 03-12-2009, 09:32 PM

4af, apparently we have an ecu that runs the carb, I have yet to see it. But other than that it controls nothing.

Rookie_One · 03-12-2009, 09:58 PM

as far as i know, the canadian spec 4A-F do not have any computer....

freakinbox · 03-13-2009, 12:36 PM

yeah I don't think it's there either. It came up on here awhile back and the guy showed pics of it and such. Makes sense though since there is a harness going to the carb. it doesn't control anything else if it is there.