Several weeks ago I was troubleshooting my a/c, heater/ defrost on here, none of which was working (neither was my fan). Well, thanks to all of your input I narrowed it down to a bad switch. I ordered a new switch from Mopar Parts America (40% cheaper than my local dealer). In the meantime, I decided to do Jim Lanes's blower motor relay fix. Well, I put the switch in today, crossed my fingers and put it on max a/c and wow! What a huge difference! It seems like it's blowing twice as hard now. It's definitely worth it and it's really not that difficult. Now, here's the problem. High is the only position on the fan switch that works. When I put it on low or medium, I don't have any air coming out at all. I thought I was pretty careful with my wiring, but obviously I missed something. Anyone have any ideas what is causing this?

 

Start tracing the power from the fuse box to the switch.

Once you've done the Jim Lane relay trick, HIGH has its own power source.(IIRC)

 

Doesn't the fan switch get it's power from the selector switch? By the way, I replaced the fan switch and it still only works on high.

 

Did you have all speeds before? if not maybe the resistor block for the different fan speeds is dead. It defaults to high.

 

Originally, everything worked. Then it became intermittent. I would turn the a/c on or the defroster and no air. I had power to the selector switch but no power to the fan switch. After I did the relay fix, I still had no fan until I replaced the selector switch. Now everything works again but I only have High fan speed.

 

blower motor resistor?

 

How do I check that?

 

I have to be honest Im not one hundred percent sure, but I know how it works... It controls voltage(possibly amperage? I am by no means an electrical guru like Jim Lane) to the blower motor allowing variations in the speed. if its bad it allows one set amount of voltage thus producing one fan speed. I dont have a factory service manual yet so I cant tell you how to test it. Somebody here will jump in and correct me if I am wrong or will tell you how to fix it!

Edit: Good grief I dont know if our trucks have a resistor or if its controlled by the switch itself... Sorry just trying to think of ideas I have run across... That tears it, Im ordering my service manual...

 

where might his blower motor fix be in the sticky?

my blower is pretty weak - i guess she could use a tune up!

 

just found it in the sticky - that looks way to advanced for me

Good luck with the fix!

 

i think this is what you're looking for... Blower Motor

 

I was just looking back at Jim Lane's write-up and on the diagram he has two relays, k-1 and k-2. But on the truck is three relays, the third one goes to the a/c cycling switch post. I don't see on the wiring diagram where that is or how it's wired up. I only have the two relays, one to the blower motor and one for the anti-feedback. It works, but I'm trying to figure out how installing those relays could cause medium and low not to work or do I have something else going on. Hi should have it's own power source now, so I don't see how they would be related.

 

It's not too bad actually. Just follow the easy step by step instructions in the write up. Took me only a few hours to dso.

The 3rd relay in his pic is for his A/C cycling switch fix. It's not related to the blower motor fix other than he mounted the relay to the same bracket as his blower moter relays.

As for your lower speed settings, you need to trace out the power to the switch to ensure you are still supplying the switch with 12v. Once rewired, the relays actually power the fan motor with out going through the fan switch.

 

i had same problem. Tie the factory hot wire in with hot wire to relay and that shoul fix your problem

 

I was just talking to my Dad about doing exactly that. We were trying to figure out if that would fix it or not. I don't understand how the blower motor gets anything but high when you clip that factory wire.