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AC Compressor will not turn on. I can trigger it on manually by jumping the relay, as seen in attached video. I took it to the dealership and they could not find any issues, but suggested replacing the compressor. I found this diagnosis not accurate as the compressor has always worked fine up until now after I have done an engine build and functions within parameters when triggered manually.
I have replaced the High pressure AC sensor in the high side line. And the AC Control Valve in the actual head unit as well.
I have seen a wiring diagram for the AC loom and the only other things I can replace besides the wiring is the ECU, the HVAC Control module, and the Compressor.
What I am asking for is what leads on the wiring harness can I test to make sure everything is getting proper continuity, as the sensors are new and there are no blown fuses. I did replace the relay with another identical one and no luck.
Any suggestions? It's getting HOT fast here in AZ, already saw 105 the other day.
Are there any conditions that need to be met in order to run the compressor that I can test for?
I suggest avoiding business with the Jerry Seiner Chevrolet Dealership in Casa Grande, AZ. I held my car until the date of my appointment and when I brought it in, they had the car for 2 weeks and did not start to work on it until day 10, when they called me to ask what work I wanted done after I had told them in person as the service worker typed it into their computer for the car's paperwork.
Do you have access to a code scanner that is the equivalent of the GM MDI2 used by dealerships? If the compressor isn't turning on there probably is a code indicating where to look. I noticed you removed the relay to use the shorting wire, did you check the relay to make sure it works? Did you check fuses F17UA (15 amp) and F22UA (10 amp)?
Diagnostic Aids
The following conditions must be met in order to turn on the A/C compressor:
• Battery voltage is between 9–18 V.
• Engine coolant temperature is less than 124°C (255°F).
• Engine speed is greater than 600 RPM.
• Engine speed is less than 5 500 RPM.
• A/C high side pressure is between 269–2 929 kPa (39–425 PSI).
• Throttle position is less than 100%.
• Evaporator temperature is greater than 3°C (38°F).
• ECM does not detect excessive torque load.
• ECM does not detect insufficient idle quality.
• The ambient temperature is above 1°C (34°F).
• Blower motor is ON.
What was your ambient temperature reading? The Outside Air Temperature sensor reading can affect whether or not the compressor is permitted to engage. If the OAT is too cool the compressor won't run. One of the issues you run into is a slow update of the sensor over a period of time when the temperature is rising. Outside Air Temperature
The outside air temperature (OAT) can be viewed on the Info Display Module . The Info Display Module shows the outside air temperature as a damped value. The time and rate of the temperature update is based on an algorithm in the instrument cluster. Factors such as last temperature reading, current temperature reading, length of time the vehicle was off, current vehicle speed, and the distance driven effect when the displayed temperature is updated. To get the vehicle to display the most accurate temperature faster, drive the vehicle. Constant moving traffic will update the display to the correct temperature more quickly than stop and go traffic. The OAT uses a filter routine to minimize false updates due to engine heat or road heat.
Vehicle Outside
• Vehicle parked more than 2 hours: The OAT updates to the current sensor reading
• Vehicle parked less than 2 hours AND the new reading is LESS than the vehicle shutdown reading:
--The OAT updates to the current reading.
• Vehicle parked less than 2 hours AND the new reading is MORE than the vehicle shutdown reading:
--The vehicle will startup with the shutdown reading. As the vehicle is driven at speeds over 19 mph (30km/h) the filter counter starts to count up. When vehicle speed is under 19 mph (30km/h) the filter counter counts down. Once the counter reaches a predetermined maximum, the old OAT is updated to the current OAT reading.
• Example 1: Vehicle is OFF for 1 hour, OAT is 70 degrees F (21 degrees C). The ambient temperature has increased during the shut down to 74 degrees F (23 degrees C). The vehicle is started, OAT will still be displayed at 70 degrees F (21 degrees C), the driver drives at a stable speed over 19 mph (30km/h) for a minimum of 3 to 8 minutes with no stops, OAT display updates to current temp of 74 degrees F (23 degrees C).
• Example 2: Vehicle is shutoff for 1 hour, OAT is 70 degrees F (21 degrees C). The outside temperature has increased during the shut down to 74 degrees F (23 degrees C). The vehicle is started, OAT will still be clamped at 70 degrees F (21 degrees C). However, this time the driver is in heavy city traffic driving for 10 minutes of speeds below 19 mph (30km/h), then drives on the highway at speeds above 19 mph (30km/h) for a minimum of 2 to 6 minutes. The OAT display updates to the current temp of 74 degrees F (23 degrees C). This time it took longer to update because of all the stop and go driving below 19 mph (30km/h). Since the OAT sensor is in the grille, the values must be filtered to prevent them from updating to false readings when there is engine heat or road heat.
Vehicle in Warm Garage
• If the vehicle is started in a garage that is warmer than the outside temperature, it may take some time to update to the new cooler ambient temperature. It may take up to 10 minutes to reach the new ambient temperature.
• Example 1: Vehicle is OFF for short time, or for overnight. Heated garage temp is 70 degrees F (21 degrees C). The outside temperature has decreased during the shut down to 60 degrees F (16 degrees C). The vehicle is started, OAT will register 70 degrees F (21 degrees C) (heated garage temperature). When driven outside the OAT will start to update lower to 60 degrees F (16 degrees C) as the sensor cools off, should take less than 8 minutes.
• Example 2: Same as above: Vehicle is OFF for short time, or for overnight. Heated garage temp is 70 degrees F (21 degrees C). The outside temperature has decreased during the shut down to 60 degrees F (16 degrees C). The vehicle is started, OAT will register 70 degrees F (21 degrees C) (heated garage
temperature). However, this time, the driver does heavy city traffic driving for 10 minutes of speeds below 19 mph (30km/h), then gets on the highway at speeds above 19 mph (30km/h) for at least 2 minutes. When driven outside, the OAT will start to update lower to 60 degrees F (16 degrees C) as the sensor cools off. This should take less than 10 minutes to reach 60 degrees F (16 degrees C).
None of the following DTCs will cause a light to be lit. The fact the unit isn't working is a warning that you need to look for them.
The following DTCs may cause the compressor to disengage:
DTC B0173: Upper Left Duct Air Temperature Sensor
DTC B0178: Lower Left Duct Air Temperature Sensor
DTC B0509: Upper Right Duct Air Temperature Sensor
DTC B0514: Lower Right Duct Air Temperature Sensor
DTC B3933: Air Conditioning Evaporator Temperature Sensor
The following DTCs will definitely prevent the compressor from engaging:
DTC B393B: Air Conditioning Compressor Valve Control Circuit
DTC P0532: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
DTC P0533: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage
DTC P0645: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit The compressor could also be locked on all the time with these 3 DTCs.
DTC P0646: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit Low Voltage
DTC P0647: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit High Voltage
The A/C compressor uses a conventional belt driven magnetic clutch to engage and mechanically turn the compressor. When the A/C switch is pressed, the HVAC control module sends an A/C request message to the ECM via serial data. If specific criteria is met, the ECM then grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the permanently grounded A/C compressor clutch. The A/C compressor clutch will then be activated.
This A/C system utilizes a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a (PWM) signal in order to determine the amount of compressor displacement. The performance of the A/C compressor is regulated based on the adjusted interior temperature.
Do you have access to a code scanner that is the equivalent of the GM MDI2 used by dealerships? If the compressor isn't turning on there probably is a code indicating where to look. I noticed you removed the relay to use the shorting wire, did you check the relay to make sure it works? Did you check fuses F17UA (15 amp) and F22UA (10 amp)?
Diagnostic Aids
The following conditions must be met in order to turn on the A/C compressor:
• Battery voltage is between 9–18 V.
• Engine coolant temperature is less than 124°C (255°F).
• Engine speed is greater than 600 RPM.
• Engine speed is less than 5 500 RPM.
• A/C high side pressure is between 269–2 929 kPa (39–425 PSI).
• Throttle position is less than 100%.
• Evaporator temperature is greater than 3°C (38°F).
• ECM does not detect excessive torque load.
• ECM does not detect insufficient idle quality.
• The ambient temperature is above 1°C (34°F).
• Blower motor is ON.
What was your ambient temperature reading? The Outside Air Temperature sensor reading can affect whether or not the compressor is permitted to engage. If the OAT is too cool the compressor won't run. One of the issues you run into is a slow update of the sensor over a period of time when the temperature is rising. Outside Air Temperature
The outside air temperature (OAT) can be viewed on the Info Display Module . The Info Display Module shows the outside air temperature as a damped value. The time and rate of the temperature update is based on an algorithm in the instrument cluster. Factors such as last temperature reading, current temperature reading, length of time the vehicle was off, current vehicle speed, and the distance driven effect when the displayed temperature is updated. To get the vehicle to display the most accurate temperature faster, drive the vehicle. Constant moving traffic will update the display to the correct temperature more quickly than stop and go traffic. The OAT uses a filter routine to minimize false updates due to engine heat or road heat.
Vehicle Outside
• Vehicle parked more than 2 hours: The OAT updates to the current sensor reading
• Vehicle parked less than 2 hours AND the new reading is LESS than the vehicle shutdown reading:
--The OAT updates to the current reading.
• Vehicle parked less than 2 hours AND the new reading is MORE than the vehicle shutdown reading:
--The vehicle will startup with the shutdown reading. As the vehicle is driven at speeds over 19 mph (30km/h) the filter counter starts to count up. When vehicle speed is under 19 mph (30km/h) the filter counter counts down. Once the counter reaches a predetermined maximum, the old OAT is updated to the current OAT reading.
• Example 1: Vehicle is OFF for 1 hour, OAT is 70 degrees F (21 degrees C). The ambient temperature has increased during the shut down to 74 degrees F (23 degrees C). The vehicle is started, OAT will still be displayed at 70 degrees F (21 degrees C), the driver drives at a stable speed over 19 mph (30km/h) for a minimum of 3 to 8 minutes with no stops, OAT display updates to current temp of 74 degrees F (23 degrees C).
• Example 2: Vehicle is shutoff for 1 hour, OAT is 70 degrees F (21 degrees C). The outside temperature has increased during the shut down to 74 degrees F (23 degrees C). The vehicle is started, OAT will still be clamped at 70 degrees F (21 degrees C). However, this time the driver is in heavy city traffic driving for 10 minutes of speeds below 19 mph (30km/h), then drives on the highway at speeds above 19 mph (30km/h) for a minimum of 2 to 6 minutes. The OAT display updates to the current temp of 74 degrees F (23 degrees C). This time it took longer to update because of all the stop and go driving below 19 mph (30km/h). Since the OAT sensor is in the grille, the values must be filtered to prevent them from updating to false readings when there is engine heat or road heat.
Vehicle in Warm Garage
• If the vehicle is started in a garage that is warmer than the outside temperature, it may take some time to update to the new cooler ambient temperature. It may take up to 10 minutes to reach the new ambient temperature.
• Example 1: Vehicle is OFF for short time, or for overnight. Heated garage temp is 70 degrees F (21 degrees C). The outside temperature has decreased during the shut down to 60 degrees F (16 degrees C). The vehicle is started, OAT will register 70 degrees F (21 degrees C) (heated garage temperature). When driven outside the OAT will start to update lower to 60 degrees F (16 degrees C) as the sensor cools off, should take less than 8 minutes.
• Example 2: Same as above: Vehicle is OFF for short time, or for overnight. Heated garage temp is 70 degrees F (21 degrees C). The outside temperature has decreased during the shut down to 60 degrees F (16 degrees C). The vehicle is started, OAT will register 70 degrees F (21 degrees C) (heated garage
temperature). However, this time, the driver does heavy city traffic driving for 10 minutes of speeds below 19 mph (30km/h), then gets on the highway at speeds above 19 mph (30km/h) for at least 2 minutes. When driven outside, the OAT will start to update lower to 60 degrees F (16 degrees C) as the sensor cools off. This should take less than 10 minutes to reach 60 degrees F (16 degrees C).
None of the following DTCs will cause a light to be lit. The fact the unit isn't working is a warning that you need to look for them.
The following DTCs may cause the compressor to disengage:
DTC B0173: Upper Left Duct Air Temperature Sensor
DTC B0178: Lower Left Duct Air Temperature Sensor
DTC B0509: Upper Right Duct Air Temperature Sensor
DTC B0514: Lower Right Duct Air Temperature Sensor
DTC B3933: Air Conditioning Evaporator Temperature Sensor
The following DTCs will definitely prevent the compressor from engaging:
DTC B393B: Air Conditioning Compressor Valve Control Circuit
DTC P0532: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
DTC P0533: Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage
DTC P0645: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit The compressor could also be locked on all the time with these 3 DTCs.
DTC P0646: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit Low Voltage
DTC P0647: Air Conditioning (A/C) Compressor Clutch Relay Control Circuit High Voltage
The A/C compressor uses a conventional belt driven magnetic clutch to engage and mechanically turn the compressor. When the A/C switch is pressed, the HVAC control module sends an A/C request message to the ECM via serial data. If specific criteria is met, the ECM then grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the permanently grounded A/C compressor clutch. The A/C compressor clutch will then be activated.
This A/C system utilizes a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a (PWM) signal in order to determine the amount of compressor displacement. The performance of the A/C compressor is regulated based on the adjusted interior temperature.
What a depth of knowledge! We are all lucky to have him as a member. I enjoy reading all of Mr. Dearborn's responses, whether I fully understand them, or not!
What a depth of knowledge! We are all lucky to have him as a member. I enjoy reading all of Mr. Dearborn's responses, whether I fully understand them, or not!
What a depth of knowledge! We are all lucky to have him as a member. I enjoy reading all of Mr. Dearborn's responses, whether I fully understand them, or not!
He even has his own city. It's in Michigan. They make Fords there.
Not to completely hijack this thread. Pulled the motor on my car and installed and scanned after my ac was not working.
I am planning on checking that I have 12V this weekend. They system needs to be evacuated to change the control valve correct?
I would assume it is throwing it code because it senses it is sending a voltage to the valve and it isn’t sensing it is closing? These valves go bad very often?
Not to completely hijack this thread. Pulled the motor on my car and installed and scanned after my ac was not working.
I am planning on checking that I have 12V this weekend. They system needs to be evacuated to change the control valve correct?
I would assume it is throwing it code because it senses it is sending a voltage to the valve and it isn’t sensing it is closing? These valves go bad very often?
An engine swap is exactly what initiated mine. What must have happened in my case is that the HVAC control must have gotten bumped and messed up the valve at some point during the process, causing an internal short. I got the same diagnostic code as well. Once I evacuated the system, replaced the HVAC control valve, and met all parameters and conditions including charging the system. It worked.
Before testing for 12v go through the parameters making sure everything is met as mentioned above in the responses. If anything is not met properly it will not even supply the 12v
Where did you get the control valve? Did you have to pull the compressor out to change. I haven’t gotten eyes on it or check it out yet. Just took a quick peak after doing the scan and didn’t see it.
Where did you get the control valve? Did you have to pull the compressor out to change. I haven’t gotten eyes on it or check it out yet. Just took a quick peak after doing the scan and didn’t see it.
The HVAC control valve can be accessed in the front right wheel well without removing the compressor. I replaced the control valve with this one https://www.ebay.com/itm/115274859891
Figured I would ask this group. Finally got around to looking at it and the connector to the service valve was hammered. Out of caution, I will also change the service valve. The wires came out of the connector when I tried to plug it. Does anyone have a pin diagram or know if it matters? It is just going to a coil?
C7 AC Diagnosis Help!
