Radiator fans active while car is "ON?" - Toyota Nation Forum : Toyota Car and Truck Forums

haux · 11-09-2009, 11:45 PM

Today I noticed something very unusual. When I turned the key to "ON" (not Start, but On), the radiator fans were turning.

I've never noticed this before. A couple of weeks ago I put new aftermarket fans in. Prior to that, I have been using fans I pulled from a junkyard in 2007. Prior to that my fans were original. And I have NEVER noticed until now that the fans were running while in the "ON" mode.

I have a feeling either this isn't normal or maybe all of my previous fans were defective in some way?

chronoti · 11-10-2009, 01:37 AM

is the engine hot? if the engine is hot enough in the on pos the fans will run.

N35QU!K · 11-10-2009, 01:45 AM

My dad was showing this yesterday when we were replacing my radiator temperature sensor:
There's a plug that plugs into the top right of the radiator (facing the front of the car) that inhibits the radiator fans from turning on. If it's unplugged the radiator fans will be continuously on, even if you've turned the key to just before ignition. Try checking if the plug is unplugged.

haux · 11-10-2009, 02:08 AM

Quote:

Originally Posted by chronoti

is the engine hot? if the engine is hot enough in the on pos the fans will run.

It was indeed hot. I had just pulled into a parking lot a minute ago when I noticed it. But I know for a fact I have had the car in the ON position before while it's been hot and have never heard the fans.

These aftermarket fans actually spin so loudly that they cause a particularly noticeable vibration that you can hear from both inside and outside the car. But my previous fans definitely *weren't* quiet enough where you couldn't hear them at all.

So this is where the confusion comes in.

haux · 11-10-2009, 02:09 AM

Quote:

Originally Posted by N35QU!K

My dad was showing this yesterday when we were replacing my radiator temperature sensor:
There's a plug that plugs into the top right of the radiator (facing the front of the car) that inhibits the radiator fans from turning on. If it's unplugged the radiator fans will be continuously on, even if you've turned the key to just before ignition. Try checking if the plug is unplugged.

I will check that out later today.

the_professional · 11-10-2009, 12:04 PM

That explains why your fans are on.
Your car is on the ON position, your car was just shut off, the block is hot, the electric fans will go on even when the engine is off,as long as there is a reading that the block is too hot.

Mine do it all the time, NYC driving, extensive idling.

ekopel · 11-10-2009, 08:32 PM

dude, also, A/C.

If you had the A/C on, it will throw the fans on as well.

(I believe).

haux · 11-10-2009, 09:50 PM

I think N35QU!K may be right about this one.

However, that connector is not unplugged. It just happens to be slightly melted. This happened a couple years ago but it seemed to work fine... until now I guess. That connector is attached to a wire going down to the coolant temp sensor at the bottom of the radiator.

I'll have to see if the dealer sells those, although I think they may just include it as part of the wiring harness. So this may have to be a another junkyard adventure.

I payed attention to a few things... and I notice now that the fans stay on continuously. They never turn off.

***JohnGD*** · 11-10-2009, 10:18 PM

Just one fan on, or both stay on? Because if the AC is on, both fans will run. Otherwise, the radiator fan will come on when the engine gets hot.

If you can get an ohmmeter on the leads then you should be able to check that the switch turns off when the engine is cold, particularly overnight.

Otherwise the engine coolant temperature switch may be stuck on. There are various different ones that might look like this $40 part:

http://www.rockauto.com/catalog/moreinfo.php?pk=939199

Quote:

Originally Posted by haux

I think N35QU!K may be right about this one.

However, that connector is not unplugged. It just happens to be slightly melted. This happened a couple years ago but it seemed to work fine... until now I guess. That connector is attached to a wire going down to the coolant temp sensor at the bottom of the radiator.

I'll have to see if the dealer sells those, although I think they may just include it as part of the wiring harness. So this may have to be a another junkyard adventure.

I payed attention to a few things... and I notice now that the fans stay on continuously. They never turn off.

haux · 11-10-2009, 10:29 PM

My A/C button remains pushed in all year 'round. But the fans still run when the key is turned to the "ON" position... even this morning, before I even started the car. It has never done this before. Which tells me something just failed very recently.

If the sensor was bad, would it also cause the fans to turn on while in "ON" mode, and while cold?

I replaced my coolant temp sensor/switch two years ago. I was thinking about putting in the old one to see if this one may have gone bad, but then I remembered that you have to drain the coolant first (I think). If I remember correctly, coolant will pour out of that hole after the sensor is removed. So, I didn't feel like messing with that tonight.

Quote:

Originally Posted by JohnGD

Just one fan on, or both stay on? Because if the AC is on, both fans will run. Otherwise, the radiator fan will come on when the engine gets hot.

If you can get an ohmmeter on the leads then you should be able to check that the switch turns off when the engine is cold, particularly overnight.

Otherwise the engine coolant temperature switch may be stuck on. There are various different ones that might look like this $40 part:

http://www.rockauto.com/catalog/moreinfo.php?pk=939199

***JohnGD*** · 11-10-2009, 11:41 PM

If your AC switch is on, and the blower motor is on too, then your fans (both of them) will run. A simple test: when cold, turn off the blower motor. And then key on. Does one fan run? Both run? None?

A bad "engine coolant temperature switch" can cause the cooling fan either to run continuously or not to run at all. Depending on how it sticks. So sounds like you have some diagnostics to do. I think you want a cold/continuity, hot/no-continuity switch.

How about using a multimeter to test things? So you don't have to remove the switch.

Quote:

Originally Posted by haux

My A/C button remains pushed in all year 'round. But the fans still run when the key is turned to the "ON" position... even this morning, before I even started the car. It has never done this before. Which tells me something just failed very recently.

If the sensor was bad, would it also cause the fans to turn on while in "ON" mode, and while cold?

I replaced my coolant temp sensor/switch two years ago. I was thinking about putting in the old one to see if this one may have gone bad, but then I remembered that you have to drain the coolant first (I think). If I remember correctly, coolant will pour out of that hole after the sensor is removed. So, I didn't feel like messing with that tonight.

haux · 11-10-2009, 11:55 PM

Ok, I just got in the car. A/C depressed, blower off. Turned key to ON, both fans began turning.

I've never used a multimeter to test anything before. How would I use it to test things in this situation?

***JohnGD*** · 11-11-2009, 12:47 AM

Both running at high speed? Or slow and lazy?

1. Pull Radiator Fan Relay #1. Does the radiator fan stop?

2. Disconnect the connector from the ECT swtich, and carefully jumper the connector side (be careful of moving engine parts and not shorting the electricals to chassis). There will be battery voltage/current passing through the jumper, so be careful.

This is to simulate the ECT switch's cold/continuity. Do both fans stop?

Quote:

Originally Posted by haux

Ok, I just got in the car. A/C depressed, blower off. Turned key to ON, both fans began turning.

I've never used a multimeter to test anything before. How would I use it to test things in this situation?

haux · 11-11-2009, 01:14 AM

Quote:

Originally Posted by JohnGD

Both running at high speed? Or slow and lazy?

1. Pull Radiator Fan Relay #1. Does the radiator fan stop?

2. Disconnect the connector from the ECT swtich, and carefully jumper the connector side (be careful of moving engine parts and not shorting the electricals to chassis). There will be battery voltage/current passing through the jumper, so be careful.

This is to simulate the ECT switch's cold/continuity. Do both fans stop?

As far as I can tell, the fans spin at full blast. So much that I can feel a vibration inside the car. And you can hear it outside as well.

1) Pulled Relay #1, Driver side fan stopped. Passenger side fan was still spinning.

2) Disconnect ECT switch connector, both fans were still spinning.

I am unsure of how to "carefully" jumper that connector without electrocuting myself, if you say that there is current going through there. While the car is "ON," can I use a flathead screwdriver to jumper it? I've used screwdrivers to jumper pins on electronic circuit boards, but I'm not sure if it works the same way or is safe to do when it comes to car stuff.

***JohnGD*** · 11-11-2009, 01:58 AM

Ok. Sounds reasonable. It's probably the ECT switch or less likely the AC pressure switch then.

** If the problem is with the ECT switch, without jumpering the cable side, the fans will not stop.

How to jumper? Basically you take a piece of wire. Like maybe 16-18 gauge. Strip off the ends. Touch the bare ends to the two metal conductors in the connector you pulled off the ECT switch. The cable side, not ECT switch side.

Yeah, I think it's pretty much the same way with a screwdriver. A wire is simpler to control however, and I don't think the screwdriver fits.

** Alternately, plug the old ECT switch you have into the cable connector. If the old switch is working, both fans should stop right there. And you know.

Quote:

Originally Posted by haux

As far as I can tell, the fans spin at full blast. So much that I can feel a vibration inside the car. And you can hear it outside as well.

1) Pulled Relay #1, Driver side fan stopped. Passenger side fan was still spinning.

2) Disconnect ECT switch connector, both fans were still spinning.

I am unsure of how to "carefully" jumper that connector without electrocuting myself, if you say that there is current going through there. While the car is "ON," can I use a flathead screwdriver to jumper it? I've used screwdrivers to jumper pins on electronic circuit boards, but I'm not sure if it works the same way or is safe to do when it comes to car stuff.