AC SOS

[Vik1318]

(07-10-2024 )walterk Wrote:  What are your pressures off and on?

Pressure stays on. Pressure on and off once it’s cooler outside and compressor will actually start cycling again. Otherwise it says on the whole time.

[Vik1318]

(07-10-2024 )Rawze Wrote:  Does the pipe at the expansion valve (easy to get to and check for) getting nice and cold when the compressor is running?. - could simply be that its getting cold, but the blend doors are hanging up and not forcing cold air thru the evap core properly.

Yes it’s getting cold and blowing cold on the inside.
What is the best way to check if the blend door is getting stuck?

[DVT873]

The compressor clutch is fed directly from the body computer. No relays or external fuses. Body computer monitors amperage going to the clutch. It will shut the compressor off if that amperage goes above or below the parameter. When it does this it does not leave much of a code. IF you have the body computer diagnostic program connected you will see a high side pressure of 6525.3 psi. Some info here.

https://rawze.com/forums/showthread.php?tid=8938&page=2

I do understand that your problem is the clutch doesn't shut off. Is that just in the bay or when you're going down the road? High humidity and ambient temps above 90 can make it tough to diagnose in the bay. Most manuals call for using high volume fans in front of the truck with the hood closed which adds to the fun.

If you haven't replaced the belt AND tensioner do that before going deeper into this. I don't see where you have. It's late and I'm whipped but the short story is belt slippage on the clutch usually doesn't make noise on serpintines. The slippage creates heat on the clutch coil, reduces compressor efficiency and will cause problems.

Post your your VIN and I can probably get you a factory AC manual and chassis wiring diagram. The wiring you can find on the body builder site but not the AC manual AFIK.

Again, change the belt and tensioner.

[Bengy88]

What dvt873 said….. also. Have you tried washing the radiator out? Sometimes it’s the simple things that get overlooked. I’ve never heard of an a/c shutting down because the fan stays on too long…. Even though it shouldn’t be staying on too long. . 275 constant high pressure at 92 degrees with the fan on all the time is high. It sounds like the high pressure isn’t dropping low enough to let the fan turn off and the longer it runs the higher its gonna get Eventually turning the a/c off from high high pressure. This being a pro star have you actually connected a laptop to it to see why it’s shutting down or is this something someone is guessing at. Can we get pictures of the a/c gauges after the truck has been running long enough for the pressures to level off? Also you need to make sure that this isn’t one of these jobs that someone got pissed off at international and started bypassing switches and shi#t. I’ve seen it over and over. But all we can do is throw suggestions at ya since our hands aren’t on the truck

[Vik1318]

Appreciate taking your time and responding to my problem.
Here’s what I found . High pressure been fixed by replacing expansion valve I. The sleeper. Now high pressure goes down as it should.
By replacing expansion valve I have another problem ac runs good on high but when I turn it down or come to the stop it will not engage again unless i unplug a high pressure switch and quickly plug it back in then it work again.
New high pressure switch. What causes that?

[Bengy88]

Maybe the evaporator is stopped up with dust and freezing when you turn the fan down on low, when you unplug the high pressure switch it could be thawing and then it works again. Just a thought

[Vik1318]

(07-23-2024 )Bengy88 Wrote:  Maybe the evaporator is stopped up with dust and freezing when you turn the fan down on low, when you unplug the high pressure switch it could be thawing and then it works again. Just a thought

Brand new evaporator along with freeze probe.

[SquareOne]

How's the drain for the evaporator? Was it cleaned or tested for any obstructions? Are you seeing condensation dripping from beneath the truck?

[Vik1318]

(07-26-2024 )SquareOne Wrote:  How's the drain for the evaporator? Was it cleaned or tested for any obstructions? Are you seeing condensation dripping from beneath the truck?

On humid day looks like someone dumped a bucket of water. Sleeper the same way.