Cooling fans running all the time

Hello,

It sounds like you have a fan cooling relay driver stuck on in the PCM and it will need to be replaced. I would try a used one.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (below).

Please let us know what you find.

Cheers, Ken

Thanks, relay's already been swapped and the ECT sensor. The computer's turning the relay on after the engine is running (around three to five seconds) I had swapped in another computer as a test and get the same results. I have probed the relay plugs with a test light and no ground on the relay with key off or on until the engine starts.

What is you unplug the sensor and start it up what happens?

The fans continue to run. The only thing that keeps them from running is pulling the fuse or pulling the relay.

How does the HVAC system work no problems I am thinking it is sending a signal from the air conditioner to turn the fans on. Can you unplug the control head to see if the fans still run?

I pulled the dash controls for the HVAC and fans are still on. Also have unplugged the high and low pressure switches on the compressor and line. Is all I should have to pull is the harness from the switch panel correct?

The codes says there is a problem in the circuit. Lets do a pin to pin check on the coolant fan wiring to see what you can find. here is a guide:

https://www.2carpros.com/articles/how-to-check-wiring

Use the wiring diagram above.

Thanks, I will try this tonight or tomorrow and post back results. I have been gone all weekend.

No problem, let me know.

Finally back to this in between weird WV weather. I have not found anything out of the ordinary in any of the tests.

It like the PCM is thinking the engine is overheating and you say you tested the wiring to the sensor? You may need a scanner that can read live data to see what the computer sees as engine temperature.

Thanks, I did, also the temperature gauge is reading correctly if that makes a difference. Tomorrow after the snow is over I am going to search through the two sides of the relay again for a short to ground just to be sure I have not missed it. I tried a second computer that was a known good one and it shows p0481, too. Last night I worked all the way back through the wires in connector C104 in the lower left of the dash for the switches.

It does sounds like you have a wiring issue. Below are the rest of the wiring diagrams for you.

Please let us know what happens.

Cheers, Ken

Thanks, I think so too. All of the wiring is stock, I cannot find anything modified or spliced. I will keep you posted. It may take a few evenings. I have considered a $50.00 engine harness from eBay just to see what happens.

Okay, it would be great to get you back on the road let me know.

Thanks, yeah my teenage son agrees! I will be in Charlotte all weekend, but back on it Monday or so.

Okay, I am a couple weeks late, but back to the car. So far no change. I have not had a chance to start through the PCM harnesses yet. If I pull the plug on the y harness to the two fans, I get a p0480 and a p0481 so it recognizes an issue in both fan circuits. Plugged back in, I only get p0481. Should I start on the circuits that tell the PCM to turn the AC fans on?

Yes, that is where I would start.

Question, would the PCM register an error if a short or bad sensor commanded the fans on?

Yes it would, let run down this guide to let you know how.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I have not gotten to work much on this one, it is driveable so I have worked on other things, but today I put a code reader on it and I can post some running data if that will help. It is showing open circuit on fan, even though it is running. My assumption is the open circuit is one of the sensors that should be closed and the open circuit is telling the computer the fans should be on. Next step I believe would be checking any circuit that commands the fan on being open?

The computer runs the fans, it sounds like its having a problem with the coolant fan control driver inside the PCM. If you checked the wiring I would try swapping the PCM out with a used one to see what happens. Here is the location.

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken

I tried one I had bought from eBay back when he got the car thinking the PCM was the issue. It showed the same error, although I could only run it a few seconds before it shut the engine down. It has the security key.

Should I try a different one? I was able to return that one.

If you have replaced the sensor and checked the wiring it only leaves the PCM.

Great, I have a programmed one on the way, I will let you know what I find.

Sounds good.

Installed the new computer and same p0481. I can post some live data from the reader tomorrow if that will help. I cannot find anything out of the ordinary yet. I have put the original computer back since it checks out because the new computer throws a p0513 for invalid SKIM key.

That code is cooling fan circuit failure we must be missing something int he wiring or the relay or fan motor is bad.

This guide will help you test the relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please let us know what happens.

Cheers, Ken

Since both cooling fans are running nonstop, would that rule out bad fan motors?

Yes, I do not think that will create the problem the system monitors the trigger side of the relays.

Thanks, as soon as the rains pass through I will get back at it, probably Friday evening. I will keep you posted.

Please do.

Sorry for the delay, life happened around here the last couple of months, my Grandmother got sick and passed at 93 years old. The car is still doing the same. Son's driving it because it is not causing an issue other than bugging me, lol. I plan to get back to running through the relay tests hopefully tomorrow night.

I am sorry to hear about your grandmother, my condolences. Please let us know if you need help with anything and keep me informed about the relay test.

So far I still have not turned up anything. I got to work on it the last couple of days and I have not turned up a short or break in the wiring. One thought I had was overcharged AC system. That does not seem to be the case either. According to my gauge, it was overcharged but after evacuating out enough to bring the low side down into the 30's, I do not have cold air, so I am thinking my gauge is bad. I am going to use dad's to refill today. Considering a radiator mount temperature sensor/relay and letting the car win, lol. Unsure about that though because it will not spin the fans when the AC is turned on.

To make sure it not a Freon issue I would get set of gauges you can find on Amazon for about $40.00 and follow this guide.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

Please run down this guide and report back.

AC is back to normal and cooling. Replaced the high pressure AC switch too while I had it evacuated. The snap has been broken since we got it and it bugged me. I did get a new code today and I think it is what I was suspecting. Today's code additionally is P0645 A/C Clutch Control Circuit Open. I am betting that is the issue and it has gone to a fail safe thinking the AC is always on. I will trace that down hopefully this week and report back.

Okay, it sounds like we are getting closer.

Back on this one at last, so far I have gone back and traced the cooling fan circuits from the fans through the harnesses through the fuses and relays and everything shows continuity where it should. The open circuit on the AC clutch has disappeared as fast as it came and never reappeared. I am still getting open circuit on fan 2. Just when I thought I was getting somewhere, lol. I am at a loss.