A/C unit is blowing warm air

We do not close. There is normally someone always here to assist but normal turn around time for questions will vary depending on your location.

Couple questions about your system. Do you have an automatic temperature control system or manual? Also, do you have dual temperature zone, meaning can you change the passenger side temp different then the driver side?

I suspect you are correct with the actuator but we just need to identify what system you have in order to confirm it. Thanks

Good afternoon.

Do you have a set of gauges that can give me the high side and low side readings of the system? I need to see those readings in order to be sure the pressures are correct.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Is the compressor clutch engaging?

As far as the blend door, can you hear it move when you command cool to hot?

https://www.2carpros.com/articles/replace-blend-door-motor

I attached a wiring diagram in case the compressor is not working.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Roy

Roy,

Thank you for getting back to me. I do not have gauges and am considering buying one of these sets the Kozyvacu ($119.00) A/C repair set or the Xtremepower set ($129.00) or do you recommend a different set? I found the link to Amazon in one of your articles.

To provide some additional information, I initially thought the driver blend door wasn't working and removed from the vehicle. I manually switch from hot to cold setting and could tell a difference. Before removing the driver vents ran hot only and now I can switch from hot to cold which on the cold setting the air is warm.

After removing blend door, I watched the video and decided to add some R134a although my gauge that came with the R134a indicated mid to upper green range. I did this to test the compressor which cycled on then stopped. I felt the tubing at the high side tube and it felt cold but then warmed up when the compressor stopped running. Tomorrow evening I will test the relays and fuse to eliminate. Please advise on the A/C repair set and I will order. At this point, my best estimate is the compressor needs to be replaced.

I appreciate your time and input.

Best regards,
Bret

The ones for 119 are fine.

Do not assume the compressor is bad at this point. That is an expensive guess as it may not be that at all.

https://www.2carpros.com/articles/replace-air-conditioner-compressor

If the compressor is coming on line when adding the freon, most likely not electrical. I attached the wiring diagram for the compressor circuit for you as well. It is in the first on my responses.

Let me know the results of the gauge readings.

Roy

Roy,

Good evening! I received my gauges this evening and completed the following:

1. Tested, 0 psi on both blue and red.
2. Vacuumed system for 30 minutes.
3. Let system rest for 30 mins, gauges held at -30.
4. Attached gauges and attempted to add Freon which would not take.
5. Started truck.
6. Removed blue adapter from low side, attached hose that came with the refill bottle, added Freon up to approximately 50 psi.
7. Low side line into firewall got cold.
8. Compressor did not cycle on.
9. Reattached blue adapter to low side.
10. Some Freon escaped, quickly closed valves.
11. Observed blue gauges decline to approximately 20-25 psi, estimate this occurred because the compressor did not turn on and pressurize system.
12. Red gauge held at approximately 20-25 psi.

Please advise as to the next step. Thank you for your time and advice.
Best regards,
Bret

Okay, the compressor did not kick in because the pressure is too low. 20 pounds on the low side and the low pressure switch will not close and turn on the compressor.

You need more Freon for the compressor to come on line.

I am concerned you had 0 pressure when you started. Did you check for a leak?

https://www.2carpros.com/articles/air-conditioner-leak-detection

Roy

Roy,

That's what I thought regarding the compressor but the low side gauge read 60 psi after filling from the can which was more than the acceptable range provided. I was concerned about overcharging even though I have only used 11 oz from the can. Should I add the remaining 9 ounces and see if the compressor kicks on?

I read the check for leaks after vacuuming is confirming the gauge holds at -30 which the system did. How do I check for leaks?

This morning we tested the system again and attached a picture for your reference.

Best regards,
Bret

The gauges are showing 0. The compressor will not come on until there is pressure.

The system holds 1.6 pounds.

Fluid Types


Refrigerant Type .................... R-134a

Important

Do not mix R-12 refrigerant and R-134a refrigerant, even in the smallest amounts. R12 and R-134a are incompatible with each other. If the refrigerants are mixed, compressor failure is likely to occur.
Capacities


Refrigerant Charge .................... 0.7 kg (1.6 lbs)

Refrigerant Charge with Front and Rear A/C .................... 1.13 kg (2.5 lb)

With the engine off and fully charged, the high and low side should read the same pressure. That pressure will be close to the ambient temperature of where you live.

Start by charging the system.

As far as a leak, I attached the guide for checking the leak with either a UV light or a bright LED light.

Roy

Roy,

Sorry I missed the leak link which I have now read. Assuming no Freon has leaked, so far I have added approximately .69 lbs. Should I finish the can (.55 lbs) or buy a second one and add until I reach 1.6 lbs? Do you recommend buying a leak detector (Elitech WJL-6000 on Amazon) before adding additional Freon?
Bret

I would continue the charge until full. Leak testing is done with a fully charged system.

Yes, the UV would be good to get. You can get them at most parts stores.

Roy

Roy,
I just send a message but not sure if it went through, please confirm.
thanks,
Bret

Just this post. Nothing from before.

Roy

Roy,

This email did not go through earlier:

I added 12oz of 134a which should be a total of approximately 1.44 lbs of Freon and enough to kick-off the compressor clutch but it has yet to turn on. Is there a way to reset the system i.e. by disconnecting the negative wire? I switched the compressor relay with the horn, the horn worked with both and inspected the compressor fuse which appears good. The low and high side gauges read 100 psi, I have attached a picture for reference. I will test the pressure sensor next in approximately 30 minutes. A reminder, I know the compressor clutch turned on, not for long, last Saturday when I added Freon but it hasn't since. Let me what you advise next.
Best regards,
Bret

Okay, first, no to the reset. There is no reset.

Go to the diagram I posted in the beginning. See the ac clutch relay. Check for 2 power with the key on. There should be 2 terminals with power.

If there is, then you need to test for power to the pressure switches as well.

Check those and let me know.

Roy

Roy,

I am having trouble testing the clutch relay, the probes on the multi-meter are too large to insert into the relay slots, same with the pressure switch. I tried inserting a wire, same problem. any suggestions?
Bret

Use paper clips into the terminals and then the probes to the paper clips.

Works very well.

Roy

Roy,

Great tip.

1. We jumped the pressure switch with a paper clip and the compressor did not kick on.
2. We then measured and had 9 V DC at the pressure switch.
3. We measured and had 10 V DC at the relay on both sides of the relay switch.
Per your websites instructions the next step is a pin to pin test.

Please advise.
Bret

Okay, your battery is very low. You need to charge it. There should be 12 volts at the relay and the pressure switch.

https://www.2carpros.com/articles/how-to-charge-your-car-battery

https://www.2carpros.com/articles/car-battery-load-test

When you install the relay and turn on the A/C, does the relay click?

Roy

Roy,

The battery (Interstate) is about a year old however the truck has been in my garage for approximately 3 weeks, except for last Saturday after I removed the blend door actuator and drove it to Advance as a test run. Other than that short hot trip, I have only run during testing so the battery may be low. The multi-meter maxed out at 10V, I will look for a different setting in the morning.

One question, I removed the driver side blend door actuator and have not replaced the part. Would not having one in the vehicle skew our tests? We may have a open circuit without the part in the vehicle which could explain why the compressor did not turn on when I jumped the switch.

Regarding the relay, I have not heard a click anytime we turned the A/C on or off. I will test in the morning.

Bret

No the blend door being removed will not effect the operation of the compressor.

Roy

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

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

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

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

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

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

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

Okay, that connector is for another option.

Did you verify both powers to the other sensor?

Roy

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

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

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

The picture is dark.

How many wires in the connector?

Roy

Roy,
I have attached a close up of the wires on the high side connector. I see red, grey and white.
Bret

Okay, that matches the diagram.

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

Roy

Roy,
Yes, we tested with two paper clips and it read 5V.
Bret

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

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

Roy,

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

Bret

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

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