2nd Gen Non-Engine/Transmission Heater/AC Fan quits

[av8r]

I'm having an odd situation.



My heater/AC blower will work fine for a few minutes then stop. On a hunch I replaced the resister block by the fan motor figuring that was the issue. Long story short, that was not the problem.



It seems that if I keep the fan to the first or second speed it will continue to run. If I switch to the third or fourth (high) speed, the fan will stop within a few minutes and not work at any speed, until I shut the whole system down for 10-15 minutes.



Before I just throw parts at this issue, I'm looking so see if anyone else has seen this issue before. Fan motor? Switch? Some other relay somewhere?





Thanks in advance.

 

[GAmes]

I think it is the fan motor. When it stops running try tapping on it, more than likely it will start running again for awhile.

 

[HHhuntitall]

I'm guessing fan motor, as well. I bet it won't restart by tapping on it, as it's probably pulling too much voltage and overheating the relay under the dash, which won't come back on until it cools off... ...

 

[hsmith]

And, make sure the connectors, both at the motor and the resistor have not overheated.

 

[mwilson]

Another vote for the motor. Address it soon or you will toast the new resistor.



Mike.

 

[av8r]

Truck is parked waiting on parts. I am not convinced it is the blower motor. The symptoms don't match. The motor (when it runs) runs strong and at full speed. It does not behave like a failing electric motor. The motor case, connections, relay (located behind the fuse box on the left side of the dash), all are cool and not acting poorly. I replaced the relay and that did not help the situation.



I have ordered a HVAC "head unit" from a used part supplier. ($65 versus $220 new) I went this way because I noticed that when the motor shut off, the AC compressor clutch clicked out at the same time. I played with the switches and got it to start again and at the same time the AC clutch engaged again.



Frustrating...

 

[HHhuntitall]

Well, that may be it. Unusual for that to quit, though... . Let us know.

 

[mwilson]

Wasn't there an issue years back with the heater blower feed and the steering column or actual ignition switch at the base of the column ??



I think that was Ram, maybe not.



Mike.

 

[mwilson]

Here's one of them, says 2002 but does illustrate the connector at the base of the column.



Just thought it might be worth a mention...



A half-cooked ignition switch might be your issue as well.



http://dodgeram.info/tsb/recalls/C11.htm



Mike.

 

[HHhuntitall]

I've seen the older blower motors draw too many amps and burn up the ignition switches. Time does that to us all.....

 

[av8r]

Well, here's where we are today: I replaced the HVAC head unit with no impact on the operation. So, I got a fan motor and replaced that. No impact.

At this point the HVAC system does not operate at all now.

One thing I did notice is that with the ignition on, the system turned on, the lights (dash lights) in the head unit come on. Weird, huh? If I turn the selector to off or the fan switch to off the internal lighting goes out.


I'm giving up at this point and taking it in to a reputable local shop that I work with. I don't have time to troubleshoot the entire electrical system.

 

[HHhuntitall]

Backfeed... . HOW? Through the ignition switch or a rubbed wire?

 

[NIsaacs]

One thing I did notice is that with the ignition on, the system turned on, the lights (dash lights) in the head unit come on. Weird, huh? If I turn the selector to off or the fan switch to off the internal lighting goes out.

That indicates a bad ground, it is using your light circuit as a ground. It still might be your ignition switch. I think it provides the ground for your heater/AC controls/switches and turns them on. Then a heavy secondary ground completes the circuit for the motor. If it is like mine, all the motor speed wires are hot with the motor switch changing the ground for the speed selected. It appears to be just backwards from normal hot, on/off switching circuits and is the ground that switches, they give me grey hair every time I work on one.

Nick

 

[av8r]

The speculation of a ground fault was correct. It was traced back to a power plug behind the HVAC head unit. The ground wire was broken in the insulation causing an intermittent fault, that could only handle a very limited amp load.