Avalon Cooling Fans won't shut off?

mnarcticcat · #1 (**permalink**) 06-13-2007, 12:28 PM

Hello,

This started 2 days ago, as soon as I turn the key to power the radio (& not the engine) the fans start right up. They will not shut off while I'm driving either. I do not have the A/C on...nothing & they stay on.

Could this be a temp sensor perhaps?

Any input would be greatly appreciated!!!!

mustang67408 · #2 (**permalink**) 06-15-2007, 12:44 AM

3. The coolant temp sensor could have gone "OPEN".

2.Usually tho it is a bad a/c pressure switch, located behind the drivers headlight near the radiator.

1. The other common thing is a ENGINE MAIN RELAY, it is located under the hood in the fuse box. It controls the fans as well.

Those are the top three things that come to mind.

mnarcticcat · #3 (**permalink**) 06-15-2007, 07:41 AM

Thankyou very much for the info.... I'm still scratching my head though on this thing.

I've talked to a few people about this that said it was a temp sensor (located near the radiator cap on the left side of the engine). This was not the problem however. I could be wrong in my assumption on testing the temp sensor but I purchased a new one from NAPA & rather than removing the one from the engine, I just unplugged wiring harness from the motor & plugged it in to the new one that I was holding in my hand hoping that if this was the problem the fans would shut off....they stayed on though

The fans do have a tendency to periodically shut off like normal. From what I can tell there's a 2 stage fan relay (orange 20/30 amp). The fan(s) are always running on high, but when working normally they usually start low.... As soon as I turn the key to the ACC position without the engine started the fans are running on high at cold start.

When you say "Engine Main Relay" do you mean the two relays that control the fans or is there one that I'm not seeing that controls them both?

Would a bad A/C pressure switch make my fans run on high if it was bad? I don't know much how these work?

Thanks again....
MnArcticCat

mustang67408 · #4 (**permalink**) 06-15-2007, 08:39 AM

It is a tricky system. The wire schematics do not show the engine main relay as part of this system, but it controls A/C fan #1, which controls #2 which controls #3.
E-mail me (mustang67408@cox.net).
I have a few PDF's that might help you to diag this.
I attached a couple of pics to start you off.