Radiator cooling fans are on all the time

[birdboyd]

Hello,

I have a 2001 Grand Prix SE with a 3.1 V6 with 81,000 miles. Tonight I noticed that the cooling fans are on all the time. When you start the engine they are off for about 3-4 seconds. The engine is cold when this happens and the air is about 20 degrees, which makes it fun to trouble shoot the problem. I tried switching out two of the three relays, but did not work. I believe they were the two 6034 relays (numbers on top) I did not have a 6032 relay around.

Anyone have any ideas on what I should look for? I just recently had the radiator flushed, but that was at least two weeks ago and it worked fine after.

How long can I drive this car with the two fans running? What am I risking? Just risking burning them up? Would I be better pulling the relays in this cold weather until I have time to fix and find the problem or just leave them in?

Any help would be appreciated. Thanks in advance.

[wlkjr]

I liked the older model GM's that the fan ran when the AC was turned on. It was easier to troubleshoot and always had air through the radiator.
The fans on my 97 don't come on quite early enough to suit me. I'd rather they run all the time than come on too late.

[BNaylor]

For one, yes the fans will probably burn out so pull the relays until the weather gets better. Normally, the cooling fan aren't needed in the cold weather if the cooling system is good.

Other than the relays in the engine compartment fuse box there are two other components involved in fan turn on. The PCM module and the engine coolant temperature sensor (ECT). The PCM may be getting an erroneous signal from the ECT. In any case the PCM is the item that really controls fan turn on/turn off. The ECT can be checked for calibration with a multimeter in ohms position. I can post the resistance values if you would like.

[birdboyd]

If you have a minute to post the ohms value and possiblely the location of the sensor or what to look for that would help out greatly. I have not purchased a manual yet for this car so I am not exactly sure where to look.

Thank you.

[BNaylor]

Originally Posted by birdboyd

If you have a minute to post the ohms value and possiblely the location of the sensor or what to look for that would help out greatly. I have not purchased a manual yet for this car so I am not exactly sure where to look.

Thank you.

The ECT is normally located by the thermostat on the intake manifold underneath the throttle body. Just follow the upper radiator hose towards the engine. You'll see the wiring and electrical connector. Here are the resistance specs:

[wlkjr]

Do you have a little more detailed info on the temps the fans are supposed to come on and go off? I would assume from the chart that the fans would turn on at least at the 212 temperature since there is no value above that. Sometimes only one of my fans operates and other times both are on. I have the Alex Peper OBDII software on my laptop and it is supposed to tell when the fans are running but sometimes it doesn't seem to indicate correctly.
I have a hard time trying to figure out when the fans are supposed to run.

[BNaylor]

Originally Posted by wlkjr

Do you have a little more detailed info on the temps the fans are supposed to come on and go off? I would assume from the chart that the fans would turn on at least at the 212 temperature since there is no value above that. Sometimes only one of my fans operates and other times both are on. I have the Alex Peper OBDII software on my laptop and it is supposed to tell when the fans are running but sometimes it doesn't seem to indicate correctly.
I have a hard time trying to figure out when the fans are supposed to run.

I believe fan turn on is more like around 220 - 225 degrees.

The PCM feeds the sensor a fixed reference voltage (VRef) of usually 5 volts when the engine is on. The resistance in the sensor is high when cold and drops as the sensor warms up to alter the return voltage signal back to the PCM. The PCM uses this changing voltage to determine engine temperature.

[birdboyd]

Thanks for your help so far.

I checked the resistance. All within spec for the temperature. Any ideas what I can try next?

[BNaylor]

Originally Posted by birdboyd

Thanks for your help so far.

I checked the resistance. All within spec for the temperature. Any ideas what I can try next?

The PCM provides lo and hi speed fan enable via a lo or ground. These outputs are independent of each other. One side of each relay Cooling Fan, Cooling Fan 1 and Cooling Fan 2 are hot at all times. All the PCM does is provide that lo or ground based on engine temperature to turn the fans on.

Check the coils of each relay for 12v and zero volts or no ground. If a ground is present on one side that is abnormal and the reason why the fans are staying on. The PCM looks suspect at this time.

[birdboyd]

Thanks for all your help bnaylor3400. It is appreciated.

Today the SES light came on while driving. I plan on taking it to Autozone this weekend to have the code read. Maybe this can help to shed some light on the issue, maybe not. First I have to change a stuck caliper. No problems for the first 80,000 miles and now everything seems to be breaking.

Where would the PCM module be located? My guess is that it is pricey. Does anyone know of these going out in this type/year car? Can I change it easily myself and is there a place to get one through?

Thanks again.

[BNaylor]

Originally Posted by birdboyd

Thanks for all your help bnaylor3400. It is appreciated.

Today the SES light came on while driving. I plan on taking it to Autozone this weekend to have the code read. Maybe this can help to shed some light on the issue, maybe not. First I have to change a stuck caliper. No problems for the first 80,000 miles and now everything seems to be breaking.

Where would the PCM module be located? My guess is that it is pricey. Does anyone know of these going out in this type/year car? Can I change it easily myself and is there a place to get one through?

Thanks again.

Hopefully the SES light will shed some light on your problem. The PCM module is located in the air box assembly. PCM can be costly if you have to go through the dealer. It can replaced DIY if it shows up to be the actual problem. Ed Morad on EBay has used PCMs for around $55.00 hopefully for your SE 3.1 model. They have been known to go bad but it is not a common problem. Normally pretty reliable. But I would double check the relays and wiring from PCM to relays in the engine compartment fuse box and make sure it is not an unwanted ground or short causing fan turn on. Good luck!

[birdboyd]

Quick update:

Today I started the car and the cooling fans were still on. Took a drive,and sometime they came off. The check engine light was on, and the code had something to do with the coolant sensor being out of parameters-- too cool. I think that had something to do with the fans being on in 15 degree weather. The light was reset and has not come back on.

Now everything works as it should. The fans turn on low when the car heats up, and stays off the rest of the time. They did not go on with either the a/c or defrost when the engine was cooler. I am not sure if they are supposed to or not. Both the defrost and a/c do work.

When the fans were on all the time, it appears that they were in high. Now they are on low when they kick in.

Now I think that I will just see what happens. It is hard to troubleshoot and diagnose something that is no longer there.

Anyone have any other suggestions?

[GregA]

Originally Posted by birdboyd

... Now everything works as it should. ... When the fans were on all the time, it appears that they were in high. Now they are on low when they kick in.

Now I think that I will just see what happens. It is hard to troubleshoot and diagnose something that is no longer there.

Anyone have any other suggestions?

I have some information about the 2001 GM Engine Cooling Systems (link below). It is for a Venture van, but after reviewing the service manuals, they operate pretty much the same. Of particular interest is when the fans would be on HIGH SPEED all the time. I would guess that whatever was causing your Check Engine light to come on was also telling the PCM to turn the fans on all the time. I guess they assume it is better to have the fans ON instead of OFF.

I would try to read the "history codes" stored in the PCM and then go from there.

Engine Cooling System

Hope this helps.

Take Care,

[birdboyd]

I have been watching the car closely now and this is what I notice:

Sometimes the fans run on high continuously and sometimes they don't. When the fans are not running, and the car is allowed to heat up, the fans turn on low and off the way they should.

I can't put a trigger on why the fans are on sometimes all the time. Next step is taking it in and having it hooked up. Right now there are no SES lights on and the car runs and drives fine, with the exception of the fans being stuck on high sometimes.

Is there something I am missing? Is this even something I should worry about? With it being intermittant do I have a loose connection somewhere?

I know that the problem is not linked to the defrost. I am not sure about the a/c.

Any more suggestions would be appreciated.

Thanks in advance.

[birdboyd]

Latest update:

I took the car into a shop and had it hooked up to see what the problem is. What they came up with is that it needs a new temperature coolant sensor. They said that the sensor would not send a signal or one that did not make sense to the computer, which would then turn on the fans to "protect" the engine, figuring it is better kept overly cool. This would be consistant in what GregA has said. They also said that a new thermostat was needed.

I am not sure about this diagnose. I checked the resistance of the sensor in the car and it checks out fine. They said they checked out something with a heat gun and it was not reading correctly. Other than that I guess it could be a possiblity. I don't belive it about the thermostat because that seems to be working like it should.

After they checked it they cleared codes. Now it is working again. I am reluctant to change the sensor until it acts up again. If I change it now and it works I will be wondering if that was the fix, or if just decided to quit acting up.

Anyone have any comments or things I should try?