Cooling fans running all the time

Tiny
KEN
  • ADMIN
I would double check the relays and do the motors work when you put power to them? If the relays are okay and the wiring is good the only thing left is the PCM being bad.
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Thursday, August 16th, 2018 AT 11:54 AM
Tiny
MKFARREN
  • MEMBER
Motors run and the PCM has been swapped with two others and get the same ODB code. Relays have all been checked and are good. Would anything in the motors or the RF filters on the motors cause it to think fan control 2 circuit is open? High pressure switch on the AC compressor is new. Low pressure switch is still the original and continuity between the two and back to the PCM checks out. PCM flips the relay turning both fans on three to five seconds after the motor is started. I have also checked wiring and fuses all the way through from the pressure switches, AC clutch relay, fan relay, PDC fuses, through to the dash fuses, connectors and to the HVAC controls on the dash using the Dodge shop manual circuit diagrams. Totally stumped. Also, the coolant sensor is new, swapped it upfront and checked its wiring expecting it to be in fail mode and running the fans. Also traced the grounds from the fans and other circuits to their ground points and continuity everywhere.
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Thursday, August 16th, 2018 AT 5:01 PM
Tiny
KEN
  • ADMIN
It sounds like the AC system can be overfilled causing the high pressure sensor to kick on the fans. Here is a guide to help us confirm the issue. When you remove the high pressure sensor wiring connector does the fan stop. Here is the location:

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

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

Cheers, Ken
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Tuesday, August 21st, 2018 AT 11:25 AM
Tiny
MKFARREN
  • MEMBER
Sorry for the long delay. Son's been driving it as is for the last 2,000 to 3,000 miles. AC has been checked as well. Could it be related to the RF filters on the fan motors? I am getting close to just putting an adjustable fan controller on it lol. I love to troubleshoot though!
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Tuesday, November 6th, 2018 AT 3:29 PM
Tiny
KEN
  • ADMIN
Yep its fun trying to get to the solution. It sounds like the PCM is bad telling the fans to run all the time. I would try a used unit to see what happens. Here is the location. Let me know.
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Wednesday, November 7th, 2018 AT 9:45 AM
Tiny
MKFARREN
  • MEMBER
I have tried two different PCM's in it a while back and both exhibited the same symptoms.
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Wednesday, November 7th, 2018 AT 5:02 PM
Tiny
KEN
  • ADMIN
It has got to be the wiring or the coolant sensor then. Here is a guide and the sensor location:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Let me know.
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Thursday, November 8th, 2018 AT 9:40 AM
Tiny
MKFARREN
  • MEMBER
I will double check the wiring, but I have replaced the sensor and the connector and the gauge is reading correct on the dash. Would that matter?
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Thursday, November 8th, 2018 AT 7:00 PM
Tiny
KEN
  • ADMIN
Can you pull the HVAC fuses o see if the PCM is getting a false signal to turn the fans on?
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Friday, November 9th, 2018 AT 11:15 AM
Tiny
MKFARREN
  • MEMBER
I can, I will do that tomorrow night hopefully.
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Tuesday, November 13th, 2018 AT 6:44 PM
Tiny
KEN
  • ADMIN
Please let us know.
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Wednesday, November 14th, 2018 AT 10:21 AM
Tiny
MKFARREN
  • MEMBER
Finally got to his car today, pulled both AC fuses, dash and PCM under the hood as well as the AC clutch relay, and I still get p0481 circuit open on the fans.
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Monday, November 19th, 2018 AT 8:11 AM
Tiny
MKFARREN
  • MEMBER
I was thinking, the 0481 is open circuit on fan 2. If I swapped the plugs on the fans, if they will reach or since 2 is furthest away, plug it to fan 1, that would eliminate the possibility of the RF module on the fan or the motor itself being the issue would it not?
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Monday, November 19th, 2018 AT 8:14 AM
Tiny
MKFARREN
  • MEMBER
Could it be the vehicle speed sensor or the intake air temperature sensor? The speedometer registers correctly though, so I'd kind of ruled that out. Same with the coolant temp sensor. I replaced it and the connector back when this all started, it was registering correctly too. I've pulled the y harness off the fans and tested it as well. I'll hit it with the computer hopefully this evening to see if it's close to ambient air temperature. I can't find any open circuits or shorts to ground. Even unwrapped the harness to the PCM.
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Saturday, December 29th, 2018 AT 10:38 AM
Tiny
KEN
  • ADMIN
I would go back and test the wiring for an open circuit. Here is a guide use the wiring diagrams earlier in the post:

https://www.2carpros.com/articles/how-to-check-wiring
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Saturday, December 29th, 2018 AT 11:26 AM
Tiny
MKFARREN
  • MEMBER
We've been driving it as is with no issues and I haven't done any more troubleshooting until something strange happened today. Couple of days ago the battery died and I happened to have another one. I dropped it in and drove it. Noticed the lack of fan noise. Pulled back in the driveway and got out the code scanner and all the codes were gone and the fan was operating normally. I figured what better time than turn on the AC and see if the fans kick on like they're supposed and they did. From the time the AC was turned on, the code is back and they constantly run. In the past I had pulled the AC controls plug and fuse and it hadn't made a difference. Could it be the AC controls aren't sending the right message to the PCM? Is there anything in the gauge cluster that is also tied to the AC controls, because when I first started it after the dead battery, the tachometer and speedometer went crazy bouncing back to their maxes and mins approximately 3 times then being normal from that point on.
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Sunday, August 4th, 2019 AT 2:03 PM
Tiny
KEN
  • ADMIN
It sounds like the alternator could be throwing AC voltage causing the mix up. lets check by following this guide.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Please run down this guide and report back.

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Monday, August 5th, 2019 AT 9:43 AM
Tiny
CALVIN ARKON
  • MEMBER
A new PCM fixed my car cost me $230.00
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Monday, December 9th, 2019 AT 12:42 PM

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