A/C blows warm only at low RPMs or at idle, blows cold while accelerating?

Hi,

It could be a few things. The first thing that comes to mind would be it is low on refrigerant. You may still have a small leak.

Next, is there anything blocking airflow from the accumulator? Also, do you hear the compressor engage when the A/C is requested? Does it seem to work at all?

Let me know as much as you can. Also, take a look through this link, you may find it helpful:

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

Let me know.

Take care and God Bless Texas (From PA),

Joe

Thanks for the input. I had a chance to look at the truck a little more and noticed that the compressor was kicking off and on constantly, probably every 20-30 seconds. Normally I would have thought that meant low refrigerant, which I suppose it could be, but that would mean a fairly significant leak, since the system was fully charged very recently.

Hi,

If that is what it's doing, suspect a leak. It doesn't take long even with a smaller leak. If it wasn't cycling like that, I would feel the same as you. However, even if it is cycling that fast, you should feel the A/C working if it was fully charged.

If you have a chance, check both high and low side pressures and let me know what they are.

Let me know.

Joe

Hi Joe. I spent some more time trying to diagnose my A/C today. One thing I should mention is that I am hearing a loud hissing sound that gets louder after the A/C is on for a few minutes, and the hissing continues for about 30 seconds when the engine is turned off or when the A/C is turned off, and slowly dies down. I'm not sure if the hissing is the actual sound of a leak, or if there is anything else that is malfunctioning in the system that could cause the sound, but the hissing is definitely related to the A/C in some way.

I also noticed that the condenser fan is not turning on. I assume that at idle, when the A/C is turned on, the condenser fan should come on immediately, but it does not seem to ever come on.

Here are my A/C pressure readings:
All readings are with engine running.

When the A/C is first turned on, the A/C quickly jumps to about 200PSI, but within a few seconds it is rapidly climbing, and within 20 seconds or so it is all the way up to 400-450PSI, and pretty much maxes out on the gauage. The low side is holding steady at 58PSI with the A/C turned on.

When turning the A/C back off and letting it settle for a minute or so, the low side is maxed out on the gauge, which is about 130PSI, and the high side sits at about 140PSI. The previous time that I turned off the A/C, the high and low side went to about 125PSI, so they seem to be consistently sitting at the same PSI as one another when the A/C is turned off.

Hi,

Unless it's about 140 degrees F, we have a blockage. The high pressure shouldn't go that high. Be careful. It could be a blockage at the orifice tube.

What is the temperature when you check it? Also, turn the system off, shut the engine, and allow it to sit for approximately an hour. Then, check the static pressure. It should be near equal on both the high and low sides.

Let me know if that is what you find. Also, if possible, record the noise you are hearing and upload it for me to hear.

Let me know.

Joe

It was around 55F when I checked the pressure, so not hot at all.
I will check the static pressure and record the sound for you.

Hi,

That is certainly off. I know when it's around 60F, the low pressure should be around 25-35PSI. High pressure should be 135-150PSI. I have a feeling there is a blockage. Either that or the system is overcharged or there is too much PAG oil in it.

Let me know what you find.

Take care,

Joe

Fixed. The issue turned out to be the condenser fan. It was completely dead and no longer came on at all. I stuck a box fan right in front of the condenser and ran the system, and the high side pressure immediately began to rapidly lower, as much as 150-200 PSI, and the A/C began to blow cold.
As soon as I would turn the box fan off, the high side pressure would quickly rise back up to 400-450 PSI.
This also explains why the A/C was able to blow cold when the truck was moving, since the natural air flow was enough to cool down the condenser. The loud hissing seems to have been a symptom of the high pressure in the system, due to the condenser overheating.

Hi,

First, I'm glad you got it taken care of. Interestingly, I was under the impression the fan was working. To add, I was having a conversation with the site owner and one of the things he mentioned was the fan. LOL See pic below from our messaging.

Regardless, take care and feel free to come back anytime in the future.

Joe

See pic below.