I need some help I am working on my 99 dodge ram 1500 van. The blower for the a/c only works on full blast the first three settings do not work. I replaced the switch (best way to describe it) on the air box under the hood which contains the coils and resistors and it worked briefly. I also replaced the relay attached to the air box as well thinking that may be the problem. im out of ideas short of buying a new blower motor, any help would be appreciated.

 

The two things I would look at first are:

The replacement "blower motor resistor pack" may be acting up or blown. Be sure the replacement pack did not go out. Double check the connection to see of any of the wires that connect to the pack look like they have been overheated and/or melted.

Also look for a negative ground wire near the body of the firewall by the HVAC box, make sure it is in good condition. The relay must have a ground in order to activate for the lower speeds. The relay default it set to allow the motor to work on high speed. So if the relay has a bad ground then it cannot trip for the slower speeds.

 

just replace the inline fuse in the resister pack get the fuse from radio shack its a thermal fuse so use the same or a little higher happy trails

 

Then that is where your problem still is. I'm sure if you inspect the connector that goes to the resistor pack (it's not a switch) you will find either burnt or corroded terminals. The dealer sells a repair pigtail kit for this connector.

 

Huh?? There is no inline fuse for the resistor pack, at least not from the factory. Maybe someone added one to your's at some point.

 

There is a thermal fuse "IN" the resister pack . It does not look like a blade fuse or one you might recognise...If I have time today I will take a picture... I have replaced the thermal fuse for other people and it works for ever .Happy Trails

 

Just google image "thermal fuse" you will find one of these fuses in the resister pack..use the same temp or a little higher ,,its the same kind of fuse that is in a hair dryer or toaster

 

Interesting, first time I was aware of this thermal fuse being used in the motor resistor packs. I typed in the Google search "thermal fuse in blower motor resistor pack".