My AC has completely gone out now. About a year ago we noticed that it wouldn't get any hot air unless the car was going down the road. If you stopped, so did the hot air. Then about a month or two ago we noticed a weird scratching/clunking sound behind the dash where all the ventilation is. Now the blower won't turn on at all. I pulled the motor off the bottom of what I guess is the blower (behind the glove box) and put some voltage on it and it turns fine. I pulled the power resistor module and visually inspected it but don't have a wiring diagram so I don't know how to test it. Would that module keep it from turning on at all? Thanks in advance for your help.

 

yes, the blower motor resistor fails because the motor draws too much when it starts up. You can try replacing just the resistor but if it fails again, the motor should be replaced also.

 

Typically multi-speed blower fans will work on the highest speed setting - this by-passes the resistor track, when the resisitor block fails.

Verify the blower works for high speed only.

 

When the resistor fails in a Caravan of that year, it fails on all speeds unless it is an auto temp system in which case it fails at medium high speed and works weather the control head is turned on or off.

 

As you can see, the blower motor actually plugs into the resistor block. Then there is a thermal fuse in the resistor that smokes when you start up the blower motor because it draws too many amps at startup because the bushings in the motor get stiff from getting moisture in them because the motor is mounted in the housing horizontally. Moisture drawn in the fresh air inlet settles in the motor and eventually causes it to fail. That's why I make the wife put the system into recirculation when she goes through a car wash.