Cooling Fan Stays On.

[HighMileage]

For some reason my fan is on all the time when the engine is running. Then,when I shut the engine off,the fan runs for about 5 minutes afterwards.

It's not a high temperature issue. It came on immediately even tho the car sat for 2 weeks in freezing temps.

I'm gonna hook up the PowerLogger shortly here and see if maybe the Fan box isn't check-marked,but it's running anyway.

Any idea what's making the fan do this?

Thanks.

 

[turbo nasty]

On the drivers side inner fender, there are some relays, and one is longer than the others.
Its plain which one i'm talking about when you see it.....that one is the fan delay relay and is notorious for water intrusion and corroding and causing fan issues.

There are 2 plugs on the bottom of it just unplug them and then see if thats the culprit.

Of course watch your temp gauage and verify the high/low fan relays are working (those are the other 2 smaller relays next to the longer one mentioned).

Most chips are around 159-165 fan turn on temp IME.

 

[HighMileage]

I see which one you are talking about. Its the longest one. The one nearest the firewall.

I turned the key ahead...fan starts.... I unplugged both plugs on that relay.

The fan continues to run.

 

[williamsGN]

http://www.vortexbuicks-etc.com/fan.htm

 

[HighMileage]

Here is some more info:

My Powerlogger sez the coolant is 55'F and rising,which is most likely true since it's 30'F outside and I ran the car an hour or so ago.

The Fan box on the Data page is NOT checkmarked. ...but the fan is on.

I've had OBD-1 ECM's go bad before. The frirt sign that it's gonna crap out is the fan stays on.

The only thing that's odd about this one is that it stays on for 5 min or so after the car is shut off.

 

[GullsGN]

Here is some more info:

My Powerlogger sez the coolant is 55'F and rising,which is most likely true since it's 30'F outside and I ran the car an hour or so ago.

The Fan box on the Data page is NOT checkmarked. ...but the fan is on.

I've had OBD-1 ECM's go bad before. The frirt sign that it's gonna crap out is the fan stays on.

The only thing that's odd about this one is that it stays on for 5 min or so after the car is shut off.

It stays on for 5 min after shut off WITH the big relay unplugged? It should not. This is the delay relay.

 

[turbo nasty]

I see which one you are talking about. Its the longest one. The one nearest the firewall.

I turned the key ahead...fan starts.... I unplugged both plugs on that relay.

The fan continues to run.

You unplugged the fan delay relay with the key on and the fans running and then turned key off and the fan ran for 5 minutes and shut off?

 

[HighMileage]

It stays on for 5 min after shut off WITH the big relay unplugged? It should not. This is the delay relay.

No. It stays on when the key is on or engine running,with the delay relay unplugged.

I then turned the key off,...the fan stopped,then I plugged that relay back in. The fan turned on and ran for 5 min.

The fan shouldn't be running since the temp of the engine is actually below room temperature.

After reading the vortexbuicks page on fan operation,it appears that the Fan Coolant Temperature Switch may be at fault. It's supposed to be right there on top of the intake manifold on the drivers side,but I can't find it. I need to look harder under the harness. I did find the CTS for the ECM,however. But that is working correctly according to the PowerLogger.

I just drove 5 miles and put the GN away in it's secure place inside...activated all anti-theft things and covered it up. It just might be sitting there covered up with the fan still running? I guess I'll find out if I have a dead battery the next time I go to drive it.

 

[turbo nasty]

then I plugged that relay back in. The fan turned on and ran for 5 min.

The fan shouldn't be running since the temp of the engine is actually below room temperature.

If you wrote the above statement accurately then the fan delay relay is bad. As far as the sensor on the manifold its a single green wire kinda below and to the driver side a lil under throttle body.

 

[HighMileage]

If you wrote the above statement accurately then the fan delay relay is bad. As far as the sensor on the manifold its a single green wire kinda below and to the driver side a lil under throttle body.

Hmmm... So you think it's the Delay Relay? But what if the Coolant Fan Temp Switch/Sensor is stuck closed? Wouldn't that be falsely telling the fan to come on? I just don't want to buy the wrong part.

The fan stayed running with the key on...delay relay unplugged.

Key off....it shut back off (delay still unplugged). I plugged it back in with key off...it ran 5 min.

I appreciate your input.

 

[turbo nasty]

Theres a schematic on the link posted above.

To rule out high temp switch on manifold simply unplug it and leave the fan delay relay plugged in.

Then do whatever your doing where it would come on and stay on for 5 minutes.

Then plug sensor back in and try it. If it changes then its possible the sensor is shorted to ground.

If it doesnt change things then it sounds like the delay causing the 5 minute run so just leave it unplugged and move on to why the fan comes on with key on and the delay unplugged.

Leave the delay unplugged and solvethe fan running at key on problem this way you can rule out the delay relay affecting normal ops.

A few ways off the top of my head with the key on no start.

Jumper on adl port and its in diag mode

The cooling fan relays (high and low) have the contacts stuck closed.

The ecm is grounding the circuit before the chip commands which means its most likely fried.

Shorted control in the wiring harness itself is shorted and the short either to ground for coil control and/or the power and switched leg feeding the NO contacts.

The wiring itself has/is been tied into a switch for forcing the fan on and that switch is on

 

[HighMileage]

Thanks for the suggestions.

I'll follow those steps and see what I come up with.

I've got to find that fan switch and unplug it. That's the first thing.

To make the fan stay on for 5 minutes,I just leave everything plugged in and shut the car off. But when the key is on,it runs and runs.

I'm hoping the fan switch is just stuck on. My wiring is unmolested,so I don't expect to find anything foul.

Thanks again.

 

[GNRick]

This is the fan switch. Has one wire going to it. It is a little hard to find. I think it is sitting verticle if memory serves (as opposed to the upper radiator hose that is horizontal where it connects to the thermostat housing). http://shop.advanceautoparts.com/we...air_18890712-p?searchTerm=radiator+fan+switch

 

[williamsGN]

Drivers side of the intake, up front by the fuel pressure regulator.

 

[turbo nasty]

As far as the sensor on the manifold its a single green wire kinda below and to the driver side a lil under throttle body.

 

[GullsGN]

No. It stays on when the key is on or engine running,with the delay relay unplugged.

I then turned the key off,...the fan stopped,then I plugged that relay back in. The fan turned on and ran for 5 min.

The fan shouldn't be running since the temp of the engine is actually below room temperature.

After reading the vortexbuicks page on fan operation,it appears that the Fan Coolant Temperature Switch may be at fault. It's supposed to be right there on top of the intake manifold on the drivers side,but I can't find it. I need to look harder under the harness. I did find the CTS for the ECM,however. But that is working correctly according to the PowerLogger.

I just drove 5 miles and put the GN away in it's secure place inside...activated all anti-theft things and covered it up. It just might be sitting there covered up with the fan still running? I guess I'll find out if I have a dead battery the next time I go to drive it.

This is why most of us just unplug the big relay. It is one of the most common causes of dead batteries. Plus it costs an arm and a leg to buy. When running a 160 stat this doesn't get used very often.

 

[HighMileage]

Drivers side of the intake, up front by the fuel pressure regulator.

Thanks for the reply. I found it. It's right there facing upright between the FPR and the plenum.

I turned the key on. The fan instantly came on. (engine is below freezing) I pulled the squeeze plug off. The fan stopped.

The problem was getting the squeeze-plug off of that switch. It's tough to get fingers in there so I used needle-nose pliers and used the steel vac lines as a fulcrum. A small piece of the switch broke off.

I ordered one from Advance auto. 3-4 days. I wonder just how much coolant is gonna come out when I remove it. I'd rather not drain my cooling system again. Maybe drain a little out?

It doesn't look easy to get to,but I've got a variety of different wrenches and sockets. We'll see.

Hopefully that switch is the prob. My guess is it is stuck-grounded,keeping the fan on.

 

[salvageV6]

If the a/c is on or the defroster is on the high side pressure switch could be closed which parallels that switch.

Easiest way to check it is to unplug the high speed fan relay as well as the delay relay and use an ohm meter on the green wire with the yellow stripe on it read that wire to a ground point with the other meter lead.

If something is shorted like the a/c pressure switch or the coolant temp. switch it will read low ohms, normally with the a/c pressure normal and the coolant temp. low enough it will read an open circuit.

 

[robzombie]

This is why most of us just unplug the big relay. It is one of the most common causes of dead batteries. Plus it costs an arm and a leg to buy. When running a 160 stat this doesn't get used very often.

X2 Mine has been unplugged for months with no issues.

 

[GNRick]

You won't leak coolant when you remove the switch. Mine also broke some of the plastic when I removed the wire. Put some sealant on the new switch. Let us know how you do.