Silverado a/c help!

[Camarowguy]

I'll admit, a/c is not my strongest subject. With that being said, I'm chasing my tail on my truck. 99 silverado 5.3 new body style. Here's what happens: the a/c will run cold and fine for 10-15 minutes and then the compressor shuts off. It will not cycle back on by itself. I can press the a/c button off for 3 minutes (timed it lol) and cut it back on and it does the same thing. Runs for little while then compressor disengages. I noticed it stays engaged longer when I had the fan speed higher. Put the fan speed on low and it may take 10 mins or less to disengage. Here's what I've done so far:

-changed switch on drier
-changed cycle switch up front by condenser
-changed Hugh pressure switch on rear of compressor.
-changed orifice tube. No trash was in it.
-new compressor belt
-sprayed water on condenser in case system was over heating. Compressor never cycled back on.
-lines are not frozen when this happens. Has .8 kg of r134a as per factory specs. Pressure never gets over 250 on high side and around 30-40 on low side.
-I changed the a/c control panel with a salvage yard unit and same result.

Any other ideas? I'm hoping not to have to change the compressor. Could it be the clutch slipping? I've looked at it while engaged and it doesn't seem to be. Also, I cannot get it to cut off at idle and I haven't put gauges on it while this happens. ????? Scratching head!

[Camarowguy]

No one?

[upflying]

Is it humid where you live? I am guessing the evaporator is freezing up and shuts off the compressor until the ice thaws. Is the drain below the evap case clear? Is it dripping a lot of water during the shutdown?

[hypurone]

Originally Posted by upflying

Is it humid where you live? I am guessing the evaporator is freezing up and shuts off the compressor until the ice thaws. Is the drain below the evap case clear? Is it dripping a lot of water during the shutdown?

This ^

You can test this by raising the temp via the temp control to see if you can avoid it freezing up and make it cycle normally...

[Camarowguy]

Originally Posted by upflying

Is it humid where you live? I am guessing the evaporator is freezing up and shuts off the compressor until the ice thaws. Is the drain below the evap case clear? Is it dripping a lot of water during the shutdown?

I'll check and see. What would make it freeze up? It drips lots of water when just idling when it's cold. I finally got it to cycle off at idle, takes a while though.

[SC2150]

What are the pressures (high side & low side when running A/C on)?

That will tell a lot.....

[ShnOmac]

Originally Posted by SC2150

What are the pressures (high side & low side when running A/C on)?

That will tell a lot.....

Originally Posted by Camarowguy

. Has .8 kg of r134a as per factory specs. Pressure never gets over 250 on high side and around 30-40 on low side.

.

[brianko]

I replaced the low pressure A/C switch on an '02 Silverado once, and wouldn't you know the cheap Chinese part was defective out of the box!

Make sure you're checking your pressure switches with an ohmmeter (esp. the low pressure switch near the drier -- this one has always seemed to be problematic on the Chevys I've owned). Just jumper the connector to kick on the compressor clutch and watch with the ohmmeter to see if the switch opens.

[Camarowguy]

Originally Posted by brianko

I replaced the low pressure A/C switch on an '02 Silverado once, and wouldn't you know the cheap Chinese part was defective out of the box!

Make sure you're checking your pressure switches with an ohmmeter (esp. the low pressure switch near the drier -- this one has always seemed to be problematic on the Chevys I've owned). Just jumper the connector to kick on the compressor clutch and watch with the ohmmeter to see if the switch opens.

For some odd reason if I just the connector on the low switch, it won't kick the clutch on. It's not freezing up as I verified the other day.

[derklug]

I have seen clutches with too much air gap that will not engage all of the time. Back probe the clutch while it is running to verify that you are getting power after the clutch has begun to cycle. If you are getting power at the clutch and it is not engaged the clutch or the electromagnet is bad. If no power, check the clutch relay and see if it is getting energized. Beyond that, you are going to need a scanner to insure the ECM is powering up the ac.