ofelas

Lemme tellya.

Changing a non AC 91.5 to factory AC (parts from a 93 AC D250) has been a real treat.

Not working yet, couple of days more I reckon...I have 72 lbs of R12 that are begging to be used.

Denis

Old thread, reading it entirely because I'm working on the same problem. Blower motor works sporadically for days, then for days it's silent. The AC hasn't worked in a while but no shop will even attempt to check out the AC unless the blower motor works. Of course, heat and defrost would be really nice this time of year!

Jim Lane

Check behind your fuse panel for burned wiring on the Heater AC fuse,

Also if it is origional, replace the blower motor, the brushes wear down and the motor becomes intermittant,
you can hit a bump and the motor will start or you can hit another bump and the blower stops, it can be this simple.

Look here.
Blower motor - Dodge Diesel - Diesel Truck Resource Forums

Jim

Denis

Thanks, Jim, I will check this stuff out! I ordered a resistor too, just in case.

rtinsley

Can someone help me with this when put the battery post on the fan comes on I unplug it from the controls but it still comes on it's like the controls on the inside of truck is bypass

fuelgauge

So I know this a very old post I'm hopin BC847 that you can direct me. I back jumped th pink with black stripe and the fan worked, according to your list I'm mot gettin juice to the ignition switch. But I cant tell why not. Ive replaced the fan the resistor yhe ignition switch and the fuse is good. As far as I can tell the ground connection is good as well. If your out there I hope you can help, this is the best trouble shooting list ive found so far.

henrynlouisvill

Frustrated with blower motor (1998 Ram with A/C and heated mirrors)

I am SO frustrated with my blower motor not working.
I know my blower works by hot wiring.
Then I replaced the Resistor Block and A/C Heater Control = no change
I have done all the BC847 steps above.
I couldn't get any step to work other than the 'Touch hot wire to the 12DG at blower motor plug.

After doing that the fan worked AND the four positions on the controller worked.
I'm thinking that this 12DG on that plug is suppled by something other than the controller switch. I'm thinking the switch just completes the circuit to ground through the controller?

I see that 12DG runs through C134 to the 12DG on the Blower Motor Relay.
I've swapped that relay out with the trailer and starter relays and no difference. I put a test probe in the relay socket and one is hot for sure.

I simply don't understand why this 12DG isn't HOT from the relay...if that's were it gets is juice.

Probe on column has tons of stuff going hot in ON position

Now, on the controller harness I see seven wires:
1) OR - Illumination Only
2) LG/Wt - A/C on/off wire = hot until know set to A/C
3) TN - 1/4 fan
4) LG - 1/2 fan
5) LB - 3/4 fan
6) BK/TN - full fan
7) BK/OR - ground
NONE of these are HOT when the ignition is in the ON position (except #2)
I'm not surprised IF they are just grounding the circuit
However, when I put an Ohm tester on the fan plug BK/TN and controller BK/TN I did not see continuity.
I don't think it matters since the 12DG coming into the fan plug is never HOT unless hotwired per BC847 instructions.

So frustrating.


A/C Controller Plug

left - Resistor plug right - blower plug