Kerley

Have any members had to replace the Ignition Switch in their Dodge Ram 2500
Cummins to repair their A/C or power to the blower motor?

cougar

Not for an AC/blower power issue. What year and what's happenin? Everything else work?

Busboy

There are 2 fuses for the blower one inside and one under the hood there is also a relay that is powered on with the ignition switch through one of the fuses.

Kerley

Cougar, Last year my a/c completely quit working, I researched and replaced the Blower Motor/w fan assy, which was working as it should when tested. I also replaced the Resistor and that was the fix for eight months, and now it is down again. I am thinking it is the Resistor again. I buy my parts online from Rock Auto. I can't remember what brand the Resistor was, as there were several to choose from. Anyway, I took a short trip, returned home and the a/c was working, I switched the Ignition key off, unloaded the truck, started the truck, and no a/c. I never moved the a/c control switch. I am thinking the problem is the Resistor, if so what is the best, most durable Resistor on the market? Also, I was searching the web and found a thread where someone said that their problem required a new starter/Ignition switch to repair? I welcome all help available, Thank you, kerley

Kerley

I checked all the fuses but I may have missed the relay. Is the relay under the dash or in the pcm? Thank you.

Busboy

The fuse in the PDC is what powers the blower motor, the fuse in the junction block fuse panel inside the truck is for the "control" of the relay and the relay is in the PDC under the hood. The relay is operated by the ignition switch so when the key is on the relay provides power to the blower motor and the ground is what is switched. With the key on there should be +12 volts at the blower motor even if it's selected off. What causes the resistor block to burn out is insufficient air flow to cool it. That can be from a partially plugged evaporator core or a bad blower motor.

Kerley

Thank you very much, Busboy;3342208 I also checked the Blower Motor for Continuity, it was replaced last year and checked out good, no shorts. I also measured the voltage between the Resistor and Key Switch in the on "HOT" position with the HVAC Control switch on "High Speed" and showed no voltage, does this reading indicate a dead Resistor?
Thank you, kerley

AlpineRAM

If you select max from your blower control the current does not go over the resistor- so if you only have max or nothing on the blower => resistor.
Nothing at all=> look for fuse and relay etc.

Kerley

Thank you,AlpineRam:3342224

Kerley

Busboy: In my owner's manual page 217, it says in Cavity 2, 10amp fuse powers the Blower Motor, Relay Coil, and Heated Mirror. Is the Relay Coil located under the hood in the PDC?

Busboy

Yes, a relay coil is almost always located inside the relay and is what pulls the relay contacts together.

AlpineRAM

Another thing to check...

See if the ground wire from the fan speed switch has continuity to ground.

Kerley

I tested the resistor and no voltage whatsoever, so I replaced the resistor, still nothing. The cab fuses are all good, so I started over beginning with the PDC, I checked all fuses and relays for the HVAC, all were good, but still no Blower, My heated mirror light comes on when turned on, so I assume that the mirrors are heated. My next move will be to remove the control switch assy. and check for voltage. If there is voltage, the fix would most likely be the switch. Am I on the right path? The information I received is very valuable to me, and I thank you all for the help.

SIXSLUG

If you have nothing past the switch, then yes, its most likely the switch...

All of this could have been checked out with a multimeter with no cost...but time.

AlpineRAM

Look behind the glove box- there is a connector between the supply for the blower and the blower- if it's shaken loose (or a damaged espar heater tries to control the blower) you'll have the results you describe.