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BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17424
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I have a 2004 silverado with manual ac controls. The mode

Customer Question

I have a 2004 silverado with manual ac controls. The mode door actuator will not budge. I replaced it with a new dorman unit with the same result. I replaced the module as well and it still won't work. I've tried the relearn procedure. temp works, recirculation works, mode doesn't. Flaps are easily moved by hand when actuator is removed. What's the procedure for testing signal voltage from the module?
Submitted: 1 year ago.
Category: Chevy
Expert:  BOBBYSS replied 1 year ago.

Hello, my name is***** for the question. Can you tell me what position the more stays in? What vents does the air come from?

Customer: replied 1 year ago.
The original actuator was stuck on front vent. Both new actuators stayed neutral and did not even attempt to calibrate. Air only comes out the floor vents.
Customer: replied 1 year ago.
I also tested the actuators with a 9volt battery outside of the vehicle and they do work..
Expert:  BOBBYSS replied 1 year ago.

Does the actuator make and noise or attempt to work even a little when you try changing the mode?

Customer: replied 1 year ago.
When connected to the vehicle 3 different actuators do not make noise or move at all. When operated with a 9 volt battery outside of the vehicle they work fine. Is there a testing procedure for the control module? As in "this purple wire should have 5 volts, this one 12 volts, this one varies between 3 and 9 volts"?
Expert:  BOBBYSS replied 1 year ago.

You need to check the voltage between the brown wire and the tan wire. While moving the more knob the voltage should vary. The other wires are positional sensor signals. Typically where he issue lies is in the fuse box under the right side of the dash. There is more than likely a bad connection or a short in that area causing this. If not then it may be the module is defective.

Customer: replied 1 year ago.
I don't recall seeing any voltage fluctuation between those two but I will recheck it in the morning and inspect the junction block on the pass. dash. I'll let you know what I find. Thanks.
Expert:  BOBBYSS replied 1 year ago.

Sounds good. I will look for your response then. If I am not online when you return I will get back with you as soon as I can.

Customer: replied 1 year ago.
I checked voltage between the tan wire and brown with white stripe. It showed 7.2 volts regardless of which mode selected. This was with the engine running and everything plugged in. I looked at the harness where it runs through the dash and towards the instrument panel and there were no rub marks on the wires. Does that mean the control module is crap?
Expert:  BOBBYSS replied 1 year ago.

Did you happen to remove the connection at the fuse box to see if the terminals in the connector were loose at all?>

Customer: replied 1 year ago.
I checked the wiring and the plugs on the right side of the dash, it's just a junction block, no actual fuses. everything was nice and clean, no overheated connections and everything seemed nice and tight. I'm doing a warranty swap on the control module in the morning and I'll be back on it tomorrow afternoon. Something else I should mention. Today I ran the codes and had a c3447 stored which is a mode actuator error if I'm reading everything properly.
Expert:  BOBBYSS replied 1 year ago.

Did you try clearing the code to see if it would come back or if the system would work?

Customer: replied 1 year ago.
Cleared the code and it came back. Module made no difference, another actuator made no difference. I'm out of ideas.
Expert:  BOBBYSS replied 1 year ago.

If you check the voltage of each wire separately at the actuator and see if any of them vary while moving the adjustment what do you get?

Customer: replied 1 year ago.
Here's what I get:
Blue wire 4.8 volts
Green wire 0 volts
Yellow wire 0 volts
Tan wire 2.4 volts
Brown wire 11.9 voltsNo voltage change in any of the above mentioned wires when mode selector is moved. You'll notice the low voltage reading of 11.9, I have an optima battery and did the test with key on engine off.