hi i have a problem with my 2000 gmc sierra. my temp and duct controls on the dash are not working. I bought a new panel and pluged in both plugs and no difference,the fan selector switch works. but the temp is stuck on hot and the vent is stuck on defrost. any help?
Year: 2000Make : GMCModel: sierraEngine: 5.3
Greetings, my name is Mark.You most likely have an "Actuator" problem. Your control head is the switch that controls motors that turn the doors on your HVAC case. There is a separate actuator for the temp door and a separate actuator for you mode selection. What I need from you is the last 8 digits of your VIN. I can then punch in the exact AC system you have for your truck. There are several models of the Automatic AC and several models of the Manual AC. This is a fairly common failure and a relatively easy repair. Let me know your VIN numbers and I look forward to working with you. Oh, and by the way. Did both of these failures happen at the same time? Did you lose the temperature control at the same time you lost the air outlet issue?Thanks,...... !!
the truck was struck by lightening,I have replaced everything all computers, like 6. dash cluster haadlight switch 4x4 selector, I have everything working execpt ac summer is coming it is time to fix it. I thought it would be the damper actuator so I pulled it off took it apart checked the motor , motor is ok saw that the bord had a burnt resistor on it. so I will send you the vin for correct replacement. does this actuator fix both problems or are they 2 different problems.2gtek19t4x1540047
Okay and thanks for getting back to me. You VIN indicates you have C60 by your RPO codes. That would be manual with the actuators.It would help to have to have a diagnostic scanner to be able to give some output commands, but considering the work you have done so far, I sure you can handle the repair. By the way, did I mention I am impressed you "restored" this vehicle from its "cardiac" arrest ? Well, I am. You should have a DVOM to measure your 5-volt reference signal to the actuators, but again, you can figure this out. Below I have included the description of your system. And below that, 2 "flow-type" diagnostic work sheets to walk you through the process. Pretty simple really. You need voltage, signal, and ground to the actuator. If the vehicle was a normal repair, I might just tell you to go after the actuators, but considering you had the massive electrical storm invade the vehicle, it could be anything. And to answer your question, you have 2 separate actuators. One controlling the heat and one controlling the "mode" door operation. I don't want to assume both are faulty, especially with the spike that you had. I am going to post 2 different posts. This one is rather lengthy with the diagnostics. The other post will include the electrical schematics and repair for the actuators. Thanks for letting me help !!Mark HVAC Air Delivery/Temperature Control Circuit Description
The HVAC air delivery electrical system consists of a control module, blower switch, mode and temperature potentiometers & (motors), recirculating outside air control push button, temperature, mode and recirculating motors that operate their respective actuators and doors.
The mode, recirculating and temperature door motors are powered by ignition 3 voltage when the ignition switch is in the RUN position. The ground path is provided by the body wiring harness junction block to ground located in the left hand upper plenum area. The HVAC control module is powered by ignition 3 voltage from the HVAC fuse located in the fuse block when the ignition switch is in the RUN position. Grounding for the module is through the same circuit utilized for the door motors.
The recirculating door motor is controlled by a signal from the HVAC control module via recirculation actuator control when the push button is activated on the control head. Also, the recirculation door motor can be controlled by the PCM/VCM which monitors the automatic recirculation switch activity (located at the bottom right hand side of the air conditioning (A/C) condenser) and will signal the door motor to the recirculating mode when the switch closes due to high refrigerant pressure. This will allow cooler air from inside the vehicle to flow over the A/C evaporator thus cooling the refrigerant temperature.
Pressing the recirculation button activates several different modes in the HVAC system. An A/C request is made anytime the recirculation button is selected. Recirculation is only available in vent or bi-level modes only. Vent and bi-level are the first 8 of 17 detents on the mode switch. Recirculation can be selected with the blower motor in either the ON or OFF position.
The mode and temperature door motors are positioned in proportion to the variable voltage signal received from the HVAC control module. Adjusting the temperature dial (potentiometer) in the control head provided a variable voltage to the door motor via temp actuator control. There is a constant 5 volt reference sent to both motors via 5 volt reference from the control module. The module uses this reference voltage to accurately determine the door motor position through a feed back temp actuator signal which also varies from 0-5 volts (Pickup). The Utilities with rear A/C and Heat use Mode and Temperature door motors that operate from the front or rear control (non-sunroof vehicles) using a 0-12 volts signal.
The mode switch will allow A/C to be directed out of any discharge vents. Even with the HVAC system off, the mode switch can still direct the ram air out of any discharge vents.
Did you review the description and operation and perform the necessary inspections?
Go to Step 2
Go to Symptoms
Verify that the fault is present.
Does the system operate normally?
Go to Testing for Intermittent Conditions and Poor Connections
Go to Step 3
Does the test lamp illuminate?
Go to Step 4
Go to Step 18
Connect a test lamp between the ground circuit of the temperature door motor and the ignition positive voltage circuit of the temperature door motor.
Go to Step 5
Go to Step 19
Does the voltage measure near the specified values when in each position?
0 V: HOT
4.9 V Cold
Go to Step 15
Go to Step 6
Measure the voltage from the door position signal circuit at the HVAC control module to a good ground.
Does the voltage measure within the specified range?
Go to Step 7
Go to Step 8
Does the drive shaft of the temperature door motor rotate?
Go to Step 17
Go to Step 14
Does the voltage measure near the specified value?
Go to Step 9
Go to Step 11
Measure the voltage from the door position signal circuit of the temperature door motor to a good ground.
Go to Step 10
Go to Step 12
Go to Step 13
Test the 5-volt reference circuit of the temperature door motor for a short to ground, a short to voltage, or an open.
Did you find and correct the condition?
Go to Step 22
Go to Step 17
Test the door position signal circuit of the temperature door motor for a short to voltage.
Test the door position signal circuit of the temperature door motor for an open, a high resistance, or a short to ground.
Test the control circuit of the temperature door motor for an open, a short to ground. or a short to voltage.
Inspect the temperature door for the following conditions:
Did you find and correct the condition
Go to Step 16
Inspect for poor connections at the harness of the temperature door motor.
Connect a test lamp between the ground circuit and the ignition positive voltage circuit of the mode door motor.
0 V: Defrost
4.9 V Floor
Go to Step 7
Go to Step 8
Does the drive shaft of the mode door motor rotate?
Go to Step 14
Measure the voltage from the door position signal circuit of the mode door motor to a good ground.
Test the 5-volt reference circuit of the mode door motor for a short to ground, a short to voltage, or an open.
Test the door position signal circuit of the mode door motor for a short to voltage.
Test the door position signal circuit of the mode door motor for an open, a high resistance, or a short to ground.
Test the control circuit of the mode door motor for an open, a short to ground. or a short to voltage.
Inspect the mode door for the following conditions:
Inspect for poor connections at the harness of the mode door motor.
Go to Step 20
Inspect for poor connections at the harness of the HVAC control module.
Go to Step 21
Repair the ignition positive voltage circuit of the mode door motor.
Did you complete the repair?
Repair the ground circuit of the mode door motor.
Replace the mode door motor. Refer to Temperature Actuator Replacement .
Did you complete the replacement?
Replace the HVAC control module. Refer to Control Assembly Replacement and Control Assembly Replacement - Auxiliary .
Operate the system in order to verify the repair.
Did you correct the condition?
34+ yrs Dealership Exp. - Fully State & ASE Certified - GM Master & GM World Class Tech
Okay, so here are some wiring schematics along with some repair procedures. Mode Valve Actuator Replacement Removal Procedure
Notice: In order to avoid actuator damage, DO NOT apply power to the actuator when it is not installed in the HVAC module.