Reatta Owners Journal

HVAC Programmer Test

The following test is intended to help determine if the HVAC Programmer is sending a variable output voltage to the blower control module to control the speed of the blower motor as it should.

This test basically takes the readings I got from the programmer in my car to give you a baseline to gauge if your programmer is working properly. There may be some tests in the service manual that are appropriate for testing the progammer but I'm not aware of any.

Put your voltmeter in a position so you can read it from the seat of the car while you operate the climate controls,

HVAC Programmer Test-3

Set your voltmeter to measure 12 volts DC. You will need a small probe for your meter to connect it to the blower module connector as shown in the photo below. I used a paper clip wrapped around the positive lead of my meter. There are small probe adapters made for that purpose. Use them if you have them.

Connect the positive probe of your meter to terminal B (Gray wire) of the blower module connector as shown below. Connect the negative lead of your meter to a good metal ground point.

HVAC Programmer Test-2

Sit in the car and turn the ignition key to the run position. Don't start the engine. My meter showed 0.12 volts with the key in the run position. Your meter might vary from this reading some but I don't think it should vary a lot.

Wait for the brake pump to stop running and then set the climate controls to ECON mode and LOW fan speed. My meter gradually climbed to 8.01 volts and remained there with the fan speed set to LOW. That voltage reading varied slightly when repeating the test.

HVAC Programmer Test-4

Next, select HIGH fan speed. The voltage on my car gradually increased to 9.71 volts and remained there while the fan was set to HIGH speed. The voltage would vary sightly when repeating the test again.

HVAC Programmer Test-5

To confirm the programmer could automatically vary the signal sent to the blower module, I set the climate control to AUTO mode and set the fan control to AUTO. Then I used the UP and DOWN temperature controls to move the temperature setting from minimum to maximum. When the temperature control was set to minimum or maximum the voltage would read highest, about 9.7 volts. As the temperature setting was moved close to the ambient temperature inside the car (68 degrees in this test) the voltage would read lowest, about 8 volts. The readings were a little erratic as the temperature setting was changed. I think the reason for that is because the feedback circuit between the programmer and the blower motor is disconnected in this test.

I think this testing will prove the programmer is sending the proper signal to the blower control module. However, it might not prove the programmer is bad. That would require more testing to determine if the problem is actually the programmer or other factors such as a bad connection or a bad ground.



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