Radiator cooling fans are on all the time

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.

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.

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.

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.

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:

http://i5.photobucket.com/albums/y186/lizzywiz/ect.jpg

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.

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.

Thanks for your help so far.

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

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.

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.:banghead:

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.

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.:banghead:

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!

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?

... 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 (http://www.my-chevy-venture.com/engine-cooling-system.html)

Hope this helps.

Take Care,

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.

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?

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?

I'd replace the ECT (engine coolant temperatue) sensor if it acts up again. Resistance can check out but it is a static check only. The PCM provides 5 volts to the ECT sensor and then the sensor sends the signal with a voltage drop back back to the PCM. It could be noisy or probably more like no signal. Maybe the electrical connector was flaky.

If you disconnect the ECT the fans will run on high all the time probably for safety purposes.

Thanks once again for your advice bnaylor3400. I think it is starting to make sense. I still want to wait until it acts up to replace it. As a learning experience I want to know for sure that is the problem. If I replace it before it starts to act up I will never know if that was indeed the issue. I think it might be though. I still say they wanted to replace the thermostat as an "add on". It seems to be working as designed.

the temp sensor is mounted on the side of the radiator below the fill cap...its tough to see...mine used to set off the fans alot....i went to a pickapart junkyard and got a good one instead of paying big bucks from gm and it solved the problem...ps i believe there are 2 temp sensors in the system..1 on the radiator and the other on the block somewhere..?? good luck

the temp sensor is mounted on the side of the radiator below the fill cap...its tough to see...mine used to set off the fans alot....i went to a pickapart junkyard and got a good one instead of paying big bucks from gm and it solved the problem...ps i believe there are 2 temp sensors in the system..1 on the radiator and the other on the block somewhere..?? good luck

I really don't agree with that. The sensor on the passenger side of the radiator is the coolant level sensor. See pic below. The ECT (engine coolant temperature) sensor is located below the thermostat housing and helps the PCM control turn on/off of the fans.

http://i5.photobucket.com/albums/y186/lizzywiz/coolantsensor.jpg

First off that is not what the GM Grand Prix service manual shows. To test what I am saying, disconnect the ECT and the fans should come up in the high speed position for safety reasons. If you disconnect the electrical connector at the coolant level sensor it won't do anything. It won't even cause the fans to come on or turn on the coolant warning light. The coolant warning light needs a ground applied to turn on. However, both sensors may trigger the coolant warning light when conditions are met like low coolant level and/or overheating.

I agree with Bob (bnaylor)that even though the ECT is checking ok on the bench, it may be breaking down under exposure to heat. I would change it if it acts up again, and if you haven't changed the T-stat within the last year, do it too while the cooling system is open. I change my t-stat every spring as regular maintenance(while checking cooling system for sludge and dirty coolant). Most people don't realize that a T-stat doesn't just open and close once. It can open and close (partially) 10-15 times per minute to properly regulate coolant flow and temperature. The bi-metal spring takes quite a beating, and can become slow or weak, restricting flow, not completely closing, or not completely opening. This could cause many problems, like weak heater output, running hot, etc.... Just my :2cents:

sorry screwed up-- your right-- what it did (coolant sensor) at the time was allow the temp to go to near the redline on the dash temp gauge...this happened a few years ago forgot the specifics of my story..sorry for confusing you..

sounds to me like whoever flushed the rad might have got debris on the end of the coolant temp sensor, u can try to remove it and clean it if NOT replace...should solve the problem....

New update 3/9/06---

Replaced the coolant temperature sensor. Torqued it down to spec found in one of these posts. Although tempted, I did not use teflon tape, per another thread due to the NPT threads. Hooked everything up and fans still were on. So was the SES light. I did notice that the temp gauge was reading warmer then before, but well within limits.

Took it to Autozone to read codes. Code read PO128-- Coolant temp always low. I told them to clear it and they responded that they couldn't due to emissions laws now. I decided that it would be worth while to rent a code reader while I was there and clear it. Once I did the fans went off.

That was yesterday. Today the car came home and the fans were on again, but no SES light. Hooked the scanner up and same code popped up. Cleared it and fans are off.

Started scratching my head. The book with the code reader said to check thermostat, it could be defective. I thought it was working, but now I don't. The first thing I noticed is that the upper hose was hot, but the lower hose was cold, and so was the radiator cap after 25 minutes of driving. It does not seem like it is circulating. So my thoughts are that it works once in a while, and the fans turn off when the PCM senses the correct temp. It gets stuck closed and the PCM reads cold temps, and throws on the fans for fail safe.

Could this be right? Could it really be something like this that I should have originally checked for? My other thoughts are that some Dexcool sludge got built up in there, or when I had the flush done it all collected in there.

So the way this car is set up, with the 3.1L, what do you think? There was no build up on the old Coolant sensor. Looked like new. Is there any other tests I should do on the thermostat?

Thanks again for everyones help. I am just trying to figure things out. I hope this is coming to an end. At least I am learning alot about my car!!

Could it be that coolant level sensor mentioned above? I believe if the thermostat was stuck closed it would overheat very quickly and blow steam. May only be opening partially.

Oops-- actually I meant to say stuck open. That way it is in a constant loop and doesn't have a chance to build up pressure or heat.

Oops-- actually I meant to say stuck open. That way it is in a constant loop and doesn't have a chance to build up pressure or heat.

If the thermostat is stuck open I would agree with the DTC error code you are getting and go with Rich's suggestion to change out the thermostat.

Is there an in car test I can do on the thermostat? I don't want to rip it out until I know for sure. However searching other posts seem to point to a bad thermostat also.

Is there an in car test I can do on the thermostat? I don't want to rip it out until I know for sure. However searching other posts seem to point to a bad thermostat also.

Not while it is installed. When pulled out you can visually inspect it. If stuck open you will see it stuck open. The test was putting it into a pan of water on the stove and heating it up while monitoring with a temperature gauge. But that was to test the opening point. If stuck open it would be moot to test anyways. Good luck!

Good morning,

Sorry I did not get back with the fix. After guessing for so long I believe I finally have it fixed. All it turned out to be was a bad thermostat. It was not allowing the car to get up to temperature. The computer would sense that the reading was wrong for how long it was running, and would throw the fans on to protect the engine. I now have a new thermostat and temp sensor (just in case) installed and it has been fine for two weeks now.

I would like to especially thank bnaylor3400 for his time and guidance. It is users like you (and many others) that make me happy to use this board.

birdboyd

Good morning,

Sorry I did not get back with the fix. After guessing for so long I believe I finally have it fixed. All it turned out to be was a bad thermostat. It was not allowing the car to get up to temperature. The computer would sense that the reading was wrong for how long it was running, and would throw the fans on to protect the engine. I now have a new thermostat and temp sensor (just in case) installed and it has been fine for two weeks now.

I would like to especially thank bnaylor3400 for his time and guidance. It is users like you (and many others) that make me happy to use this board.

birdboyd

You're welcome and glad you got it resolved. Thanks for the feedback.

yep, we appreciate the feedback, it's nice to hear we got you fixed up.