Automotive Air Conditioning Information Forum

JohnHere wrote: ↑Mon Jul 18, 2022 7:46 am Adding to what has already been said:

70monte wrote: ↑Sat Jul 16, 2022 3:41 pm Well, the AC charge was evacuated, and I vacuumed the system down for 30 minutes and then let it sit for 30 minutes. The pressure decayed slightly so I vacuumed again for about 20 minutes and let it sit for about another 20 minutes and the pressure held. I recharged it with 45 ounces.

The vacuum dropping slightly was a sign that air and moisture were still present in the system. Hopefully, you got them all out with the additional 20-minute evacuation.

70monte wrote: ↑Sat Jul 16, 2022 3:41 pm I had him do this again a little later and the low side would drop to about 22 and the high side about 250 and then the cycling switch would kick the clutch off.

We're not concerned with idle-speed pressures because the compressor isn't doing very much at such a low RPM. But at 1,500 RPM and an ambient of 96°F, that's fairly normal operation, and the pressures look pretty good at this point. Earlier, though, they're fluctuating abnormally. The question is, why?

The cycling switch and/or the PCM are turning off the compressor so that the evaporator doesn't freeze up, blocking airflow.

70monte wrote: ↑Sat Jul 16, 2022 3:41 pm The lines coming out of the accumulator were cold and so was the line that was going into the heater box or whatever it is called that attaches to the firewall and houses the blower motor. I did notice that there was cold air coming out around that line which did have some foam around it but was missing some at the top. I don't think air should be coming out of there but I don't know. The other side of that line was hot after the connector, and I believe the orifice tube is located in that portion of the line.

The lines you mention being cold is good. The line from the condenser up to the OT being hot is also good. However, you shouldn't feel any cold air coming out around the line extending from the blower housing. I would seal-up that opening with a suitable caulking or foam.

70monte wrote: ↑Sat Jul 16, 2022 3:41 pm Vent temps at 1500-1800 rpms got down to 57 degrees and at idle were around 60-62 degrees out of the center vent with AC on max and high blower. We took the truck for a drive and vent temps stayed around 69-73 so I'm assuming the clutch is cycling on and off pretty rapidly. Not sure why it's cycling so much at higher rpms. Could the cycling switch be going bad?

Those vent temperatures are not acceptable for a properly operating system. The compressor on your truck doesn't have a control valve, either. It's possible that the cycling switch is going bad, but it seems to me that it's doing its job as intended.

70monte wrote: ↑Sat Jul 16, 2022 3:41 pm So basically we are back to square one. Not sure what the next step is.

At this point, with a truck that has about 230,000 miles on it, I would recover the charge, pull the OT, and examine it. If the OT screen is full of gunk and even some metal particles, that would indicate the compressor is on its last legs. In such a case, I would replace the compressor with a brand-new unit (not rebuilt), the condenser, OT (specs call for a red one), accumulator, and flush or replace the liquid line between the condenser and the evaporator depending on whether it has a muffler. If it has a muffler (I don't believe it does), you'll need to replace the line because mufflers can't be flushed.

70monte wrote: ↑Sat Jul 23, 2022 9:35 pm Prior to me going out of town, I told him it was possible that his compressor is weak and needs to be replaced because of the mileage of the truck and he has no idea if it was ever replaced. He has already bought a replacement compressor and accumulator and plans to install them at some point. The location of the compressor is at the bottom of the engine and is not very accessible at all so it's not going to be a fun job.

JohnHere wrote: ↑Sat Jul 23, 2022 10:59 pm

70monte wrote: ↑Sat Jul 23, 2022 9:35 pm Prior to me going out of town, I told him it was possible that his compressor is weak and needs to be replaced because of the mileage of the truck and he has no idea if it was ever replaced. He has already bought a replacement compressor and accumulator and plans to install them at some point. The location of the compressor is at the bottom of the engine and is not very accessible at all so it's not going to be a fun job.

With such high mileage, it's a good idea to replace the compressor, especially because we don't know the history of the existing compressor. I would also replace the condenser at the same time. Most compressor manufacturers require that the condenser be replaced along with the compressor to maintain the compressor's warranty. In addition, the condenser acts as a filter for any debris that the old compressor might have shed. Any such debris can and does block the small tubes in the condenser and will compromise system performance. There's also a high probability of ruining the new compressor if any debris is left in the system.

Don't forget to replace the orifice tube as well. I don't remember anymore, but have you pulled the old one to check its condition?

tbirdtbird wrote: ↑Thu Aug 11, 2022 2:10 am John had already suggested to replace comp due to high mileage, guess it grenaded anyway before you could get to it.
Unless you have specialized flushing equipment from HECAT, condensers need to be replaced, and the hoses flushed well or replaced. You have been on here before so you already know this.

https://www.ackits.com/pulsator-kit-the ... hine-31646

There is also the flushing forum.
BUT the problem is the owners, don't allow it to become YOUR problem...just replace it

tbirdtbird wrote: ↑Thu Aug 11, 2022 7:43 am "The compressor did not make any noise so if it grenaded, it did it quietly."
They can do that. No where else that trash on the OT can come from

JohnHere wrote: ↑Thu Aug 11, 2022 12:05 pm If it's a parallel-flow condenser--and it most likely is--it really can't be flushed. Good decision on replacing it especially since you've taken it this far. Would be a shame not to replace it, and then the compressor gets ruined again. I also advise replacing the accumulator because moisture will contaminate the desiccant inside while the system is open.