AC Compressor

[Schurkey]

I hooked up the gauges (following a video) with nothing running... ...Temp was about 85 F and 37% relative humidity.

How warm was the engine compartment? If the engine has been running--or even getting a heap of solar radiation--warming-up the underhood equipment, your pressures will reflect the temp of the system, not the ambient temp.

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Based on the 158-psi indication, the engine compartment must have been about 115 degrees. Seem reasonable?

Flush the system next?

Not my first choice, since it's got refrigerant and enough pressure to run the compressor. Find out why the compressor doesn't work.

perfectly normal for the gauges to read the same pressure when the system has been sitting static

Yup. High side at 158, low-side needle pegged 'cause the gauge doesn't go to 160.

That's not too much pressure to try and run the system?

Nope. When running on a hot day, the high-side can go over 300 psi.

Where is the LP switch connector?

Probably on the accumulator / receiver-dryer. Didn't you replace that? Did you transfer the low pressure cutout switch from the old one? (Or am I thinking of another person with A/C issues?)

Not when ambient temps are high, use the chart posted here,

AC clutch cycling on low fan setting.

Hi guys, I just finished redoing my AC. In my 99 2 door Tahoe with no rear AC. I went with a Delphi compressor, ACdelco dryer, hoses and a rockauto condenser and a 4 seasons orifice tube. Everything went smooth..added 32 oz of Freon and it’s blowing really good. Only issue I am having is the...

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Thanks for that. I've saved that chart for future reference.

 

[MBRZ71]

How warm was the engine compartment? If the engine has been running--or even getting a heap of solar radiation--warming-up the underhood equipment, your pressures will reflect the temp of the system, not the ambient temp.


Based on the 158-psi indication, the engine compartment must have been about 115 degrees. Seem reasonable?

Maybe.

Not my first choice, since it's got refrigerant and enough pressure to run the compressor. Find out why the compressor doesn't work.


Yup. High side at 158, low-side needle pegged 'cause the gauge doesn't go to 160.


Nope. When running on a hot day, the high-side can go over 300 psi.


Probably on the accumulator / receiver-dryer. Didn't you replace that? Did you transfer the low pressure cutout switch from the old one? (Or am I thinking of another person with A/C issues?)

I think that's someone else. I haven't replaced anything yet, once I get a multimeter on that plug I can figure out if I need a new LP switch. I'll check the accumulator area.

Thanks for that. I've saved that chart for future reference.

 

[Ranger550]

Nice to know about the Sanden 4440 compressor. I'd never heard of them before.

 

[L31MaxExpress]

Do you have a volt meter? Now that you proved you have pressure (lots of it), you can start up the engine and turn on the A/C. If the compressor doesn't run, pull the LP Switch connector and see if you have voltage on one of the leads. If so, try to jumper the connector and see if the compressor runs. If so, you probably have a bad LP Switch. If not, go to your service manual and trace down further in the circuit(s) to find the culprit. Good luck!

On a Vortec the low pressure cycling switch on the accumulator is a ground, the high side binary pressure switch on the back of the compressor is the +12V A/C request signal.

 

[L31MaxExpress]

Nice to know about the Sanden 4440 compressor. I'd never heard of them before.

4261 is the same compressor with a smaller pulley. Works well for guys with dual evaporators or a lot of idle time.

 

[Ranger550]

4261 is the same compressor with a smaller pulley. Works well for guys with dual evaporators or a lot of idle time.

Not my 1998 K-1500. It's just a standard two-door, three-person, long bed with nothing extra. Back window behind my head. Old-School, but so am I. LOL!!!

I will indeed keep the Sanden in mind, as I do occasionally work on other people's auto A/C systems, although I am retired now. I have all the A/C equipment like a vacuum pump, gauge sets, and an OBD II Innova, that go can go back to OBD I.

 

[MBRZ71]

On a Vortec the low pressure cycling switch on the accumulator is a ground, the high side binary pressure switch on the back of the compressor is the +12V A/C request signal.

So ultimately I need to check for power at the compressor connector? I did try to run it and jump the relay like it showed in the video and the compressor didn't engage. I'm thinking the compressor is bad, I have no real reason to think I bought it with a good compressor.

A lot has been said about the sanden compressors. South AZ gets hot in the summer and I may want an upgrade. Is there any breakdown on the differences for the sanden compressors that work with these trucks?