Diagnosing AC Trouble

[16FujiDisco]

Had these symptoms on my Silverado and it was the compressor. Turning A/C off then on worked for a bit, but it finally conked out for good.

 

[RoverTide]

I’m actually experiencing the same exact problems. Have also put a set of manifold gauges on and checked pressure with my IID tool.

IID showing around 140 driving.
Manifold gauges were showing 55/240 at around 100° F.

I haven’t added any refrigerant or done any leak testing.

I also only experience the problem after my car has been running a long time, however, my AC compressor hisses after I shutdown my car now. It hisses for about 30 seconds after shutdown.

I’m pretty sure it’s the compressor but it seems like it’s a royal pain in the ass to replace, and not exactly cheap.

I’m going to see if it’ll go for the rest of summer here and proceed from there. It does seem to be getting worse though.

For that temperature, your low side pressure looks correct, but your high side does look a little low..... Have you confirmed the HVAC blend doors are in the correct position using the gap tool?

Regarding the hissing, my research tells me some hissing is normal when you shut the car off... its basically the low side and the high side pressure equalizing when the compressor shuts off. Not sure how to tell if its normal or abnormal though.

On mine, I am really hoping for the expansion valve to be the culprit, but I am afraid I have a weak compressor. I have watched the 2 youtube videos on compressor replacement, and the pain in the ass factor is really high on that job.... even for a land rover.

Anyone know of a way to diagnose the electrical components using the gap tool? I have been monitoring the various HVAC ventilation live values, and I really can't make sense of the ones that seem important. i.e. compressor amps shows 0.75 amps constant???.... seems oddly low. Compressor psi shows readings all over the place with no relation to the cold air blowing from the vents or the ambient outside temp???... Makes me wonder if there is some sort of sensor problem, even though its not throwing any fault codes.

 

[Rover Range]

Make sure your motor mounts are not sagging.
This will cause the engine to drop down, causing the mechanical fan to hit the fan shroud and not turn.

 

[f1racer328]

For that temperature, your low side pressure looks correct, but your high side does look a little low..... Have you confirmed the HVAC blend doors are in the correct position using the gap tool?

Regarding the hissing, my research tells me some hissing is normal when you shut the car off... its basically the low side and the high side pressure equalizing when the compressor shuts off. Not sure how to tell if its normal or abnormal though.

On mine, I am really hoping for the expansion valve to be the culprit, but I am afraid I have a weak compressor. I have watched the 2 youtube videos on compressor replacement, and the pain in the ass factor is really high on that job.... even for a land rover.

Anyone know of a way to diagnose the electrical components using the gap tool? I have been monitoring the various HVAC ventilation live values, and I really can't make sense of the ones that seem important. i.e. compressor amps shows 0.75 amps constant???.... seems oddly low. Compressor psi shows readings all over the place with no relation to the cold air blowing from the vents or the ambient outside temp???... Makes me wonder if there is some sort of sensor problem, even though its not throwing any fault codes.

Our vehicles have variable output compressors.

Diagnosing Variable Displacement Compressors | MOTOR

In earlier air conditioning systems, the compressor ran at full capacity whenever its cycling clutch was engaged. If the engine was running and the clutch was engaged, the compressor was pumping. And the faster the engine turned, the more pressure the compressor developed. The only way to...

www.motor.com

I think this is why the pressures vary a bit, and we can’t rely on using a standard chart of pressure vs temperature to diagnose.

I did a little searching on some of the Facebook groups and it seems like faulty compressors are the majority of these problems.

 

[lmwong]

My AC has been acting up much like OP describes. I have to turn off and on the AC, maybe multiple times to get AC to blow cold. When I run the faults with the GAP tool I get the below HVAC errors. Will replacing the compressor fix the issue(s)? Thanks.

 

[powershift]

I'd replace the battery unless it is known good and reset the codes to see if they come back.

 

[jlglr4]

@lmwong Most of these codes seem to relate to the instrument panel. If you haven’t already done it, I would clear all of the codes, then use the car and run the codes again. See if anything shows up. Then try to reproduce the problem, and run the codes again and see what shows up. You might have a short or a bad switch in the instrument panel someplace.

 

[lmwong]

@lmwong Most of these codes seem to relate to the instrument panel. If you haven’t already done it, I would clear all of the codes, then use the car and run the codes again. See if anything shows up. Then try to reproduce the problem, and run the codes again and see what shows up. You might have a short or a bad switch in the instrument panel someplace.

I ordered a replacement HVAC instrument cluster and installed it today. It fixed the issue! All codes cleared. Thank you!

 

[jlglr4]

That’s great. If you could post the part number that you replaced, it might be helpful to someone in the future. I’m guessing it was HVAC Temperature Control Panel - LR070848.

 

[lmwong]

That’s great. If you could post the part number that you replaced, it might be helpful to someone in the future. I’m guessing it was HVAC Temperature Control Panel - LR070848.

That is indeed the part number. I bought one off eBay from a wrecked 2016.