A/C unit is blowing warm air

Tiny
BWILKINSON05
  • MEMBER
Roy,

We retested the battery, pressure sensor and relay with a different multi-meter:

Battery = 12.4V
Pressure sensor = 4.8V
Relay = 13.8-14V

I reviewed the "air conditioning not working" summary on your website and the pressure sensor test results indicate the climate control computer is bad. Do you agree? What do you recommend at this point?

Best regards,
Bret
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Saturday, July 18th, 2020 AT 7:49 AM
Tiny
ASEMASTER6371
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Okay, did you test the 2 wire sensor or 2 wire? The 2 wire is a low pressure switch. It should have 12 volts with the key on.

The 3 wire sensor run on 5 volts. The reference and signal wires should both have 5 volts. The remaining wire is the return wire to the module.

Please tell me how you determined the module was the failure?

Roy
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Saturday, July 18th, 2020 AT 7:56 AM
Tiny
BWILKINSON05
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Roy,

We tested the pressure sensor near the fire wall which I believe is the low side pressure sensor. It has two ports and read 4.8V with the key on. Where is the 3 wire sensor?
Bret
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Saturday, July 18th, 2020 AT 8:04 AM
Tiny
ASEMASTER6371
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Okay, I stand corrected. The 2 wire you checked should be 5 volts. Jump the terminals together and see if the compressor runs.

The 3 wire is at the compressor. It should be on the high side line. It could also be at the front as well. I attached pictures for you. That will have 2 5 volt feeds.

Roy
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Saturday, July 18th, 2020 AT 8:22 AM
Tiny
BWILKINSON05
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Roy,

We double checked and confirmed the high side connector was two pins. When we jumped I notice a slight draw on the motor but the clutch did not turn on.
I test the three pin connector near the compressor, see attached picture and it read 5V. I also noticed but did not test a connector on the compressor.
Bret
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Saturday, July 18th, 2020 AT 8:28 AM
Tiny
ASEMASTER6371
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Okay, did you jump the 2 wire on the low side? It should be by the dryer assembly.

Were there 2 5 volt feeds a the pressure sensor?

Roy
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Saturday, July 18th, 2020 AT 8:38 AM
Tiny
BWILKINSON05
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Roy,

We jumped the low side pressure sensor connector in the attached picture, I noticed a slight draw on the motor but the clutch did not kick-on. There is a second connector near the low side sensor, see blue connector in picture but I do not see a place to plug in.

Bret
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Saturday, July 18th, 2020 AT 8:45 AM
Tiny
ASEMASTER6371
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Okay, that connector is for another option.

Did you verify both powers to the other sensor?

Roy
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Saturday, July 18th, 2020 AT 8:49 AM
Tiny
BWILKINSON05
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Roy,
I just tested the blue connector in the picture and it read 0V. I just noticed it this morning, not sure why it's there.
Which other sensor are you referring to?
Bret
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Saturday, July 18th, 2020 AT 9:05 AM
Tiny
ASEMASTER6371
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LIke I said, forget about that connector.

The 3 wire sensor on the high side line by the condenser in the picture I posted.

Roy
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Saturday, July 18th, 2020 AT 9:16 AM
Tiny
BWILKINSON05
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Roy,
We tested the high side pressure connector which read 5V, see picture which I believe matches the location #4 and #5 in the #3 diagram you sent at 8:22 this morning.
Please advise.
Bret
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Saturday, July 18th, 2020 AT 10:04 AM
Tiny
ASEMASTER6371
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The picture is dark.

How many wires in the connector?

Roy
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Saturday, July 18th, 2020 AT 10:06 AM
Tiny
BWILKINSON05
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Roy,
I have attached a close up of the wires on the high side connector. I see red, grey and white.
Bret
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Saturday, July 18th, 2020 AT 10:15 AM
Tiny
ASEMASTER6371
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Okay, that matches the diagram.

Do you have 2 wires that show 5 volts with the key on?

Roy
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Saturday, July 18th, 2020 AT 10:36 AM
Tiny
BWILKINSON05
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Roy,
Yes, we tested with two paper clips and it read 5V.
Bret
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Saturday, July 18th, 2020 AT 10:37 AM
Tiny
BWILKINSON05
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Roy,
For reference, on occasion (over 2-3+ years), the HVAC system would blow hot air when set to cold. The immediate fix was to turn off the vehicle and turn back on. Most of the time this reset the system. This issue could have been caused by the Climate Control Module but we thought it was the driver blend door because the driver side was the only side running hot, passenger was normal. This is why we removed the blend door when we started diagnosing the current problem. As you recall the HVAC unit without the blend door blew warm air on both sides with the blend door manually set to the cool position.

Also, the blower motor resister would burn out approximately every 1-2 years which would turn off the fan. Either the replacement blower motor resister was not a quality part (BWD from Advance) or I figured the unit was frying due to another component.

Based on our testing and the low side connector reading 5V versus 12V comparing to your websites "Air Conditioning not working" instructions, I thought this may indicate the Climate Control Module needs replacement or further testing:

"A pressure sensor is used to measure the amount of refrigerant is in the system. When this sensor goes bad the compressor will not turn on. To test this sensor remove the wiring connector and insert a jumper wire between the two terminals of the connector. If the compressor turns on the sensor is bad or the system is low or overcharged. If nothing happens use a test light to see if there is 12 volts at one of the wires. If no power is present suspect the climate control computer being bad."

Is there another test we can run to isolate the Climate Control Module to evaluate? All other tests seem indicate the system is running properly from an electrical perspective. Let me know what additional tests you recommend we run.
Thank you for your input.
Best regards,
Bret
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Saturday, July 18th, 2020 AT 11:44 AM
Tiny
ASEMASTER6371
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Please, I asked you for the voltages at the 3 wire sensor. Do you have 2 5 volt wires?

I know you are stuck on the module but we are not there yet.

As far as the resistor failing often, that happens from a blower motor drawing too much current. when I find a bad resistor, I replace both the motor and resistor.

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

Roy

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Saturday, July 18th, 2020 AT 12:05 PM
Tiny
BWILKINSON05
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Roy,

I tested the high side connector with 3 wires. I show 5V from one point and 0V from the other two.

Bret
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Saturday, July 18th, 2020 AT 12:25 PM
Tiny
BWILKINSON05
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Roy,

We ran another test to check the compressor. We jumped the relay with a paper clip and the compressor clicked. With the jumper in place the clutch also engaged while the vehicle was on.
Bret
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Saturday, July 18th, 2020 AT 2:12 PM
Tiny
BWILKINSON05
  • MEMBER
Roy,

Here is the latest update:

1. I jumped the compressor relay with the paperclip
2. The Freon had run low so I added a new can 12 oz and the remainder of the A/C Pro can, approx 6-8 oz.
3. Allowed the system to run for awhile, please see charge levels which I believe are spot on per the gauge manual.
4. As a test, I removed the paperclip and the compressor clutch stopped, kept jumper clip installed.
5. The air in the cab was cool but not extremely cold at the lowest setting of 60 F
6. I believe this rules out the climate control module and indicates a switch is bad, I guess I would start with the low side.
7. Is it a fair estimate the relay is okay, if I switched with the horn relay and the horn works with both?

Thank you for your comments.

Bret
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Saturday, July 18th, 2020 AT 3:36 PM

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