corvette95

Got my old actuator back together, gonna try to jump it to battery tomorrow to verify actuator or programmer. I did plug it up tonight and it would again move, but only to hot

corvette95

Took the programmer apart, seems one of the capacitor was burned , I resolder it and test both of the blue corner resistors, both show 12.5 volts in 12.5 +/- out. I can GROUND tan/black and yellow wires at actuator, it moves both ways, I can ground the same wires at the programmer and the actuator moves (so no broken wires) again, now that programmer is fixed, swapped control head again, still no change, will only move to hot!

engle1147

Good to hear your actuator was not totally trashed. Now it just sounds like you've just got a stuck button or problem in/on the control head. Take it apart to see what is up or swap it out with a "good" spare if you have one.

SunCr

What's the outside air temp? At anything but 60 or 90 on the Controls, it's going to work the Door depending on what the Outside and Inside Temp Sensors are showing. So, if the signal is particularly cold, you'll get heat, even at the lower settings. Now at Auto 60 or 90, it's suppose to ignore the Temps Sensors and default to a/c or heat. However, if it's really cold - or just below 50 degrees - the Low Pressure Sensor contacts on the a/c low line are going to be open and the compressor isn't going to engage - at least not until there's some engine heat to raise the static charge of whatever gas it's using. If it doesn't have a full charge - or any gas, it's probably not going to come on at all.

davesabo

same car- 1989 - same issue
blend door doesn't move.
I am going to check the rod, but where is this programmer? and can it be replaced ( is the part available? )

when you say ground the tan/ black wire and then the yello wire, this is at the connection for the blend door motor correct? the door should move when grounded,, does the car have to be running> or just ignition on. thanks

Cliff Harris

There are two 140 ohm resistors that affect the movement of the blend door motor. If one of those resistors is open then the blend door will move to one extreme and stay there. Measure the resistance of the two resistors on the 200 ohm range of a digital meter. They are the two large resistors in the lower left corner of the HVAC programmer PC board (they get very hot and discolor the PC board):



The programmer is mounted on the firewall above the gas pedal. It is held in place by one 7mm screw.

There is a hidden clip or nut buried in the middle of the colored vacuum tubes that must be removed to unplug the vacuum harness. Here's a picture of the vacuum harness after it is unplugged (clip buried in the middle of the tubes):

davesabo

are there any forum members that do blend door 'programmer' repairs?

Cliff Harris

I found a HVAC programmer and actuator from a Buick at the junk yard. They are the same as the Olds and Cadillac units and mount directly on the heater housing (behind the glove box). There is no PC board on the motor like the Corvette units. There are several wires that solder directly to the motor and position feedback potentiometer. The wires plug in to a connector on the HVAC programmer PC board. I thought it was interesting that the part number on the label on the motor is the same as the one in my Corvette.

The motor, gear train and lever appear to be the same, so it should be just a matter of some unsoldering and soldering to make it work. "Just" is relative, I guess -- I've been soldering for over 50 years.

Justin Schmidt

Just took my system apart inherited an 89 grandpa could never figure out what was wrong. Turned out program board one of the resisters had a bad solder to the board simple clean off and flow new solder fixed! (If everything tests right look at the back of the board would have been super easy to miss.