Troubleshooting Astro Van Heating Problemsby Don Bowman
The heating system on an Astro van starts at the water pump, where the water is picked up and transferred through a hose to the heater core. The water runs through the heater core and returns to the Astro's intake manifold on the engine side of the thermostat housing. The heater core and the air conditioning evaporator share the same housing under the dash but are in separate compartments.
The blower motor is located in the part of the housing located under the glove compartment. The motor is on the bottom of the housing with the drive shaft extending upward with a circular fan attached to it into the housing. Slightly to the left and behind the motor is the blower motor resister that controls the fan speeds in conjunction with the fan speed switch on the dash.
There are several doors in the housing that turn the air on and off and control the location of the airflow on the dash. These doors are controlled with the control panel on the dash that in turn sends a signal to a series of electric motors or vacuum solenoids, depending on the year of the vehicle. The function of these motors or solenoids is to open or close the appropriate doors in the housing to direct the air to the desired location.
If the fan does not come on, check the fuses located in the van under the driver's side dash or on the driver's outside of the dash between the door and the dash. If they are good check the relay for the interior fan. Check the fan itself with a circuit tester and make sure the fan is getting power. If it is getting power, then the fan motor is bad. If the fan motor only worked on one speed, the blower motor resister is bad and needs to be replaced.
If the fan motor works but the location of the airflow can not be changed, the blend door motors or vacuum solenoids must be checked for operation. Pull the glove compartment box out and the motors or solenoids will be visible. With the engine running, move the controls and watch for them to move. If they fail to swing the arm for the doors to open, check to see if they are getting power or vacuum. For power check with the circuit tester, and for vacuum simply pull the line off and check for vacuum problems. If there is no power and the fuses are good, then the control unit on the dash is bad. If there is no vacuum, check the vacuum source--a small vacuum line running through the firewall to the engine manifold or T'd into the power brake vacuum booster.