My AC/Heater (fan on)is acting up again.... The fan doesnt go on all the time when I start the truck.   I replaced the Fan motor and the speed control dohickey  awhile ago, that wasnt the problem

 

After I drive for awhile 2 - 5 minutes the fan will go on, start blowing air..... I thought it might be the control knob assembly on the dash( on off ac/ heat/ fan speed) but I dont think that's the problem either.

Its been working good for many months , now again in the AM or if I park the truck for a couple hours and start it, not even touching the control knobs , The AC and fan doesnt go on untill I drive a few miles and then it goes on and works / blows cold are fine.

 

Any Ideas what is causing this? Anyone else have this exact issue and found the fix ?

Edited July 22, 20195 yr by GSP7

 

Check the 40A fuse #12 in the PDC.

Replace the blower relay.

I would check for vacuum leaks.

1 hour ago, Mopar1973Man said:

 

 

Check the 40A fuse #12 in the PDC.

Replace the blower relay.

Hey Mike ,

 Ok,  I pulled and checked the blower motor fuse , Its good, reinstalled it.

 Pulled the Blower Relay and reinstalled it .  Everything is clean and looks good

 

So far now at home everytime I turn the ign key on the Blower motor has been going on OK

 

Didnt go right on this morning, 6:00 am,  till I got a few miles from my house, same about 11:00 when I left the job site , it went on several miles down the road. Acted up yesterday too

 

How much $ are those relays to replace.  They all appear to be the same part number.

I thought Relays either worked or completely do not work, Not on / off like a stuck switch

 

I'll keep posted if when it acts up again and wont go on again

 

.

33 minutes ago, NIsaacs said:

I would check for vacuum leaks.

Vacuum has nothing to do with the fan coming on.

 

34 minutes ago, GSP7 said:

Hey Mike ,

 Ok,  I pulled and checked the blower motor fuse , Its good, reinstalled it.

 Pulled the Blower Relay and reinstalled it .  Everything is clean and looks good

 

So far now at home everytime I turn the ign key on the Blower motor has been going on OK

 

Didnt go right on this morning, 6:00 am,  till I got a few miles from my house, same about 11:00 when I left the job site , it went on several miles down the road. Acted up yesterday too

 

How much $ are those relays to replace.  They all appear to be the same part number.

I thought Relays either worked or completely do not work, Not on / off like a stuck switch

 

I'll keep posted if when it acts up again and wont go on again

 

.

Swap a different relay in the PDC like the horn relay and see if it works better. They are all the same.

 

It is possible for anything mechanical to fail slowly or instantly.

 

Or it could be a bad or dirty connection hence why it seem to work after you pulled the fuse and relay and put them back in and itworked better for a while.

Next time it does it have a volt ohm meter handy.  Now, with the key in the on position and the fan speed switch turned to max the dark green wire at the fan motor should have 12+ volts.  If no, check fuse #12 and fan relay in the PDC or the dark green wire for open circuit.

 

If yes, 12+ volts, then ohm test the black/tan wire with the fan switch still at max and the connector unplugged from the fan motor.   One terminal of the VOM on the black/tan wire and the other to ground.  There should be near 0 ohms.  If yes, then there is a bad fan motor. 

 

If no, then there is an open circuit in either the black tan wire to  A/C heater control, the A/C heater control, or the black/orange wire from the A/C heater control to the ground at right dash center support.          

9 minutes ago, IBMobile said:

Next time it does it have a volt ohm meter handy.  Now, with the key in the on position and the fan speed switch turned to max the dark green wire at the fan motor should have 12+ volts.  If no, check fuse #12 and fan relay in the PDC or the dark green wire for open circuit.

 

If yes, 12+ volts, then ohm test the black/tan wire with the fan switch still at max and the connector unplugged from the fan motor.   One terminal of the VOM on the black/tan wire and the other to ground.  There should be near 0 ohms.  If yes, then there is a bad fan motor. 

 

If no, then there is an open circuit in either the black tan wire to  A/C heater control, the A/C heater control, or the black/orange wire from the A/C heater control to the ground at right dash center support.          

 

Thanks IBmobile

"When it happens " is the big challenge to checking/testing.....Usually its hot out (100*) and I just want to get home from a job site fast as I can, no time to relax and test till I get home and relax.... So far evey time I check stuff its working again .....

 

I all ready installed a New Fan motor and speed control

 

How do I get to this ( "ground at right dash center support" ). ?

I can't help you with the heat.  I've worked up in your area in the summer...no thanks.

 

I know you installed those new parts but I tried to take you through the diagnostic process so no steps are missed.  

 

This shows where the ground is located under the dash.  It looks like a PIA to get to. 

If you find that the ground   (black/orange) wire from the A/C heater control is the problem then just run a new ground straight down on the left center dash support and ground it on the dash frame near the power outlet.

 

IBMobile

 

If I pulled the Dash/ instrument bezel off , do you think the ground would be right there?...

Out looking at my dash ...Or maybe the cup holder assembly, looks maybe like it can be removed separate, and ground stud look like, just above that ...? ?....

 

I need to check the ground...  If I cant get to the ground.... Would running another ground wire right off the Blower motor wire harness below the glove box be the thing to do?

 

Last couple days the AC f blower has been working ok , today leaving the job site about 11:00  it didnt go on when I turned on the ignition key . I Cycled the ignition key a couple times, and messed with the AC/Heater controls and It went on.

 

I was wondering if the problem was the Relay in the control center/ fuse box. It seemed to work a couple days after pulling the relay and reinstall.... Think Ill swap the horn relay this week end

 

Ugh !

Rick

Edited July 26, 20195 yr by GSP7

Update: 

I was off monday and didnt drive of start my dodge all weekend. So this morning I turned the ignition switch on with AC on and Blower on high and nothing/ no blower. So I cycled the ign key a few times, started the truck a few times , still no AC blower motor.

 

So with ign off I pulled the blower relay in the under hood fuse box, tapped on it and reinstalled. Then turned the ign on and the AC blower motor went on...... Hmmm ... coincidence or bad/sticky relay?

 

Well I swapped the tow relay with the blower relay and we'll see if it cures the issue..... Started the truck , ign on off a few times and the blower is still going on every time (for now).

 

I added a can of R134 cause I was low..... and blower still working monday morn...

 

Well see what happens Tuesday....Supposed to be high 90*s- 100* all week

 

Edited July 29, 20195 yr by GSP7

Just replace the relay.

.

Edited July 30, 20195 yr by GSP7