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The HVAC cluster is not working. Sometimes when you turn off the car and restart it will start working. You cannot turn on the fan at any speed, cannot turn on the air conditioner, no rear window defroster and so on. The car is a 2003 Pontiac Grand Prix.
Re: The HVAC cluster is not working. Sometimes when you...
The first step is to check all the fuses also check in the engine compartment for another fuse box. the problem may just be a fuse or may be the control.
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Test the electrical circuits ! Manual HVAC or automatic HVAC ?
Do you know the difference ? Heater / A/C blower motor electrical control diffrent . Manual has resistors an a relay for different speeds , automatic has a blower motor control module .Free wiring diagrams here http://www.bbbind.com/free-tsb Enter vehicle info year , make , model and engine size . Under system click on HVAC ,then under subsystem HVAC controls will pop up . Click the search button , then the blue links . First off you need to know what system yours has , manual or automatic. GMC Yukon HVAC Blower Motor Won Turn On Blower Motor Problems Auto Repair Help
Check engine light ,abs , air bag lights etc.... come on when key turned on ?
Fuse IPC/HVAC BATT 10 amp located in the left IP junction block . Do you know where this junction box is ?
Does the heater an A/C work ? If so the fuse isn't the problem .
Speedometer
The speedometer is a road indicator. The vehicle speed sensor (VSS) is a permanent magnet generator which is located on the transaxle. The VSS sends an input to the PCM whenever the transaxle differential carrier turns. The PCM then buffers the VSS signal. The PCM transmits the VSS signal to the following components at 4000 pulses/mile through CKT 817:
• The instrument cluster
• The cruise control module
• The radio (uplevel)
The instrument cluster uses the input in order to indicate the vehicle speed on the speedometer.
Instrument Cluster Indicators
The BCM controls the instrument cluster indicators through the SPI serial data communication bus. Refer to Body Control Module System Check in Body Control System.
IPC/BFC ACC
10A
Instrument Cluster and Body Control Module (BCM)
IPC/HVAC BATT
10A
Instrument Cluster and Heater A/C Control Assembly
You may not have to. If the blower resistor is near the blower motor that should be tested first(cheaper part too). Sometimes they go and the result is a one speed or no speed fan.
Your impala doesn't have a resistor , it has a blower motor control processor and it doesn't work the way you think it does Chevy Trailblazer EXT Blower Motor Won Turn Off
Blower Motor Control Processor
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a PWM signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
the fan relay(resister) that control fan speed is probably burned out.When this occurs it will only blow at high speed because its getting 12volts directly to the fan
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