Cooling fan problem

[millbrilesabre]

So I've been having a problem with the left side cooling fan not turning on. I noticed that if I had the engine running and the AC turned on, the fan would be off. but if I reached down to the plug and pushed in or lifted up on it, the fan would turn on. Then when I let go of it the fan would turn back off.

Today I removed the fan to try and see if I could find a bad connection on the fan side of where the plug connects. On the bench I hooked up to a 12 volt power supply, and it powered right up. I could not replicate the problem. No matter how I wiggled or messed with the plug, the fan stayed on. I also checked the other side of the plug and everything seems fine there. The terminals are not loose and spread open or anything like that. It feels the same the one on the working side. When the AC is on and I'm checking for voltage I cannot get it to lose voltage by wiggling the plug or the wires or anything like that. So I'm stumped. Does this sound like it's just the motor itself? Why would it work on the bench and not in the car? I did try running some jumper wires directly from the battery to the fan while it was installed in the car and that did not work.

Correct me if I'm wrong but I'm pretty sure the fact that it's getting 14 volts at the plug means that there's no issues with any of the relays and I can bypass all of that troubleshooting. Plus the fact that wiggling the plug made a difference points to a mechanical issue.

Oh I forgot to mention, there's nothing I can do now to get it to turn on. After removing it and reinstalling it, I'm still getting 14 volts at the plug but I can not get the fan to turn on at all anymore, even with the trick that was working before by just pulling up on the plug. The only thing I did when I removed it was took it apart and sprayed contact cleaner all over everything and then put it back together.

 

[millbrilesabre]

Well it turns out one of my wires for the left fan was shorting to the bottom of the radiator. The radiator had cut into the insulation. Wrapped it with electrical tape and now I have 2 fans again! Hopefully now my ac will be cold while idling again, it's been 117°F here the last couple days!

mods can delete this thread if you want

 

[millbrilesabre]

Turns out that was not the end of my cooling problems.

After that repair, everything was working great for about 1 day. I tested it by idling in the heat for a long time and watching the temp gauge, and everything stayed normal and comfortable. It never went above 205 and the ac stayed ice cold.. Then within a couple days I started noticing the problem returning. The car.was running hot and the a/c getting warm while idling. This is what was happening when I only had 1 fan working, but now it's worse. Both fans are still running now, but they must not be running at the proper speed because they are not working effectively. And now I'm also getting a p0481 code which comes and goes, and I wasn't getting that before. Even though it was running hot before, it never went above the upper 230s. Now the temp will go up to upper 240s while I'm idling. Which still says "normal" but when I shut off the car yesterday at 248, the coolant started boiling out of the radiator.

idk how fast the fans are actually moving but the reason I'm convinced they're the problem is because all of these heating issues go away as soon as I start driving at a steady pace, creating passive airflow through the radiator and condenser

This car has been in multiple accidents before. And it wasnt properly repaired, i just bent shit back to where i felt it was good enough lol... So I'm sure the 1st wiring issue had something to do with that, wouldn't be surprised if there is another wire problem somewhere. I've already replaced 2 relays, swapped the other with a known good one. Any suggestions on what to look for, more specifically than that?

This doesnt sound like a water pump or thermostat issue, does it? I cang remember when the water pump was last changed but I think it's been installed for a very long time. But I believe the coolant is flowing. I'm sure it would be overheating worse if it wasn't, right?

 

[RD_Atlanta]

I think that I agree with your logic in that since increasing the air flow (at higher speeds) through the radiator lowers the temperature that you need to increase lair flow at lower speeds. My suspicion is your fans are running on low speed (which is essentially both fans connected in series via the relay circuit design).
I attached the following files:
1. A schematic of the fans circuits.
2. A white paper which explains the P04 PCM Fan Logic (which is the PCM which the LeSabre's use)
Your largest help will be the attached schematic. I included ID numbers & part numbers for the (3) relays in the schematic so that you can confirm the correct relays are installed and in the correct socket.

A few more points to consider:
- While I do agree with your logic that there is not enough air flow through the radiator at low speeds, it would not hurt to perform a stove test with your thermostat (especially as easy as it is to remove on these cars). It's nothing more than observing it in a pan of water (on the stove) with a candy style thermometer. I prefer to purchase a new thermostat and test both just to have a visual comparison. The thermostat should begin to open at its advertised temperature but most importantly that it opens all the way (which is where its beneficial to have a new one to compare it to).
- I will follow with another post explaining how I prefer to change the programmed control logic for the fans, why I think this is needed and how to perform the change. For now, hopefully hat I have provided here will help you to troubleshoot the problem.

 

[RD_Atlanta]

This is the follow-up that I promised in my previous post on the cooling fans programming....

I prefer for the cooling fans to come on at a much lower temperature than what is setup from the factory. The problem is, by default, the P04 PCM doe not have control of the cooling fans. Instead they are controlled the BCM. I change it to where the PCM tells the BCM to allow the PCM to control the cooling fans. This way, I can set the cooling fans to run at the temperatures that make more sense to me. How significant is it? I think it's a major risk as to how excessively high that I've seen the coolant temperatures reach before the BCM commands the cooling fans on. Before I switched over to PCM control. I could sometimes see the coolant temperatures reach 210 degrees F before the first fan was commanded on.

Now that the PCM is in control on all of my LeSabre's...
- I have Fan-1 set to turn on at 89.5 deg C (193.1 F) then off at 87.5 deg C (189.5 F)
- I have Fan-2 set to turn on at 92 deg C (197.6 F) then off at 90 deg C (194 F)
- Then both fans off when the car is above 45mph. then resume temperature control below 40mph.

Regardless of the GM 3.8L being such a durable engine, I think permitting any engine coolant temperatures to rise so high is just not a good thing to do. And subsequentially helps the 4T65e to last longer.

As for how to make the change: Have a look at the attached PDF. I can only speak for where these settings are physically located within the Jet software GUI. However, these settings are all part of the P04 PCM OS used in your 2005 LeSabre, so these same settings should be located somewhere within the HPT GUI once you have your file open. Be sure to save the file to a different name so that you'll always have a copy of the file that your buddy modified for you (the calibration that you are running) to resort back to if ever needed. Once you have the settings changed and pushed to your PCM, it's easy to check that the fans are working in accordance with your settings by monitoring the coolant temperature that the PCM sees on your onboard dash monitoring system (if you your LeSabre has it) or you can use a scanner.

8/14/2025 Edit to the above: Everything above is accurate except where I refer to the default control of the fans coming from the BCM. In reality, there is no BCM on the 00-05 LeSabre's. I have since learned that the 'traditional' BCM functions have been distributed between 3 control modules (the Dash Integration Module, the Rear Integration Module & the Instrument Panel Controller (which is a daughter board)). This isn't all that important, it does not change anything previously stated, the fan logic resides outside the PCM be default and I firmly think its better to switch it to the PCM where you will know for certain at which temperature point the fans turn on. One final point, the term BCM has become a paradigm of sorts. So, if you look for the DIM module (which resides behind the glove box), it will be most often referred to as the BCM on Ebay.

 

[millbrilesabre]

Update - looks like it was just a fuse. I hadn't bothered to check them because the fans were both running, I assumed that meant the fuses were ok. But after studying the wiring diagram enough to understand how these relays work, I realized my assumption was wrong.

Turns out a bad fan2 fuse would only cause the 2nd fan to stop working when the ecu tries to switch them to high speed. And then when the ecu sees 0v at that fan, it triggers the p0481 and defaults back to low speed.

I just found a blown fuse for fan2 and replaced it. Will update again if it keeps blowing

 

[RD_Atlanta]

Update - looks like it was just a fuse. I hadn't bothered to check them because the fans were both running, I assumed that meant the fuses were ok. But after studying the wiring diagram enough to understand how these relays work, I realized my assumption was wrong.

Turns out a bad fan2 fuse would only cause the 2nd fan to stop working when the ecu tries to switch them to high speed. And then when the ecu sees 0v at that fan, it triggers the p0481 and defaults back to low speed.

I just found a blown fuse for fan2 and replaced it. Will update again if it keeps blowing

That's great news. If it continues to blow the fuse, these fans are available in bone yards.