A/C unit is blowing warm air

Tiny
BWILKINSON05
  • MEMBER
Roy,

I tested pin 43, it read 9.5v which indicates the relay is sending power to the ECM (I will charge the battery). What triggers the ECM to communicate with the high side (pressure) sensor?
Bret
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Friday, August 14th, 2020 AT 8:05 AM
Tiny
ASEMASTER6371
  • EXPERT
The ECM will ground that pin once it gets the correct signal from the pressure sensors. That leads us right back to the beginning. Without power at the sensor, that wire will not be grounded by the ECM.

Roy
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Friday, August 14th, 2020 AT 8:12 AM
Tiny
BWILKINSON05
  • MEMBER
Roy,

The two components I see sending signals to the ECM currently are the low side sensor and climate control module? Does it make sense to replace the low side sensor as a process of elimination? If not, what is my next step?
Bret
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Friday, August 14th, 2020 AT 9:01 AM
Tiny
ASEMASTER6371
  • EXPERT
No, we have been over this so many times. The issue is the pressure sensor that has not voltage to the one pin we have been discussing.

Roy
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Friday, August 14th, 2020 AT 9:05 AM
Tiny
BWILKINSON05
  • MEMBER
Roy,

Yes, I understand. What signals the ECM to generate 5V at pin 14? Based on the schematic, I see three signals sent to the ECM - from the HVAC control module, from the low pressure sensor through the HVAC control module and the fuse block. We confirmed the a/c comp relay is working by testing pin 43 which leaves the other two as options unless there are other inputs that send signals to pin 43. Please advise what you recommend as your next step?
Bret
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Friday, August 14th, 2020 AT 11:50 AM
Tiny
ASEMASTER6371
  • EXPERT
The internal circuitry inside the ECM is what generates the 5 volts.

Roy
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Friday, August 14th, 2020 AT 11:56 AM
Tiny
BWILKINSON05
  • MEMBER
Roy,
FS1 did not provide any comment or support on pin 14. Since the ECM's are providing the same result i.E. 0v at pin 14, I wonder if the ECM is not receiving the correct data at pin 58 or upstream from the ECM.
Bret
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Friday, August 14th, 2020 AT 12:08 PM
Tiny
ASEMASTER6371
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Pin 58 has nothing to do with the 5 volt signal at all.

Roy
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Friday, August 14th, 2020 AT 12:14 PM
Tiny
BWILKINSON05
  • MEMBER
Roy,

After considering all the circumstance of my HVAC unit, I decided to replace the climate control unit and fortunately it solved the problem. We did have to add a little Freon but afterwards everything seems to be running well and we have not detected any leaks. I will keep you posted and appreciate your help with this project.
Bret
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Monday, August 17th, 2020 AT 10:59 AM
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Roy
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Monday, August 17th, 2020 AT 11:56 AM

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