i have a 91 aerostar 4.0 ext. i've been trying to improve its sluggish heater/fan. i get 4 distinct fan speeds when i turn on the fan and use the high-low selector switch, but even at its highest speed it doesn't seem to be running fast,or pushing much air. i replaced the fan motor, no change. does anyone know what else could cause slow fan speeds? battery too weak? fuse is correct per label on dash...switch seems to select different speeds..am i missing something or out of luck? rick

 

I wonder if all the air doors are opening like they should?

 

The first thing I would check is the wiring too the blower motor itself. If you put an aftermarket motor on, like I just did with my Ranger, they can be wired to rotate in either dirction. And since there are only two wires at the motor itsef, it can be easy to get it one way and have it rotate backwards. If reversing the wires does not produce a signifigant increase in air volume, the next step is the resistor. That little sob is what controls voltage to the blower motor from your control **** on your dash panel. It will be located somewhere close to the motor on the plenum of the heating/cooling system, as a matter of fact, will be the only electrical connection in the plenun besides that of the blower motor. That should be the next possible step, since, like I said before, it is the next thing in line in the system! Hope this helps!

 

Hey I just got done fixing a Cutlass that had the same problem. The heater box was full of pine needles and all the air couldnt get thru. Removed about five good handfuls of needles and presto you could fly a kite in front of the vents, where it hardly messed up your hair before
Do you park under pine trees ??

Sparky

 

thanks for the ideas guys, no pine trees here in the yard. but checking for debris in the plenum sounds like a good idea, while i'm there i'll look for the resistor block, how would i check it?.. i'll probably open up the dash this wkend, time and kids allowing..rick

 

The resistor is very similer in function to the old points ignition resistor, but with 3 or 4 (can not remember, do not have my old one in front of me right now) coils in it instead of one. Other than the fans speed from the selector switch on your dash, I don't really know if there is any tried and true test. Other than it will have the same type of effects of failure, either it burns out a coil and does not work, or it does work, but with fan speed either at a slower setting or one of the higher settings not working, dependent on which coil did burn out. Make any sence? Kinda frustrating, isn't it?