AC Trouble Shooting, 2005 Suburban LT

[project_x]

I have a new to me 2005 Suburban LT 4x4 with Auto HVAC and rear air

The AC is blowing hot air.
1. Fuses and relay are all good and tested.
2. AC clutch isn't working.
3. I jumped the low pressure switch to see if the clutch engaged, it did not.
4. I put a set of gauges on the system...pressure was 0...so system is empty.

Should I put a vacuum on the system and see if there are any leaks before changing the clutch/compressor?

What would be the best plane of attack?

 

[OR VietVet]

Put the vacuum pump on it and check to see if it holds vacuum and while you are doing that trace the wires from the low pressure switch and check for problems. Apply 12 volts to the clutch to see if will engage. If you get it to engage, see if the compressor turns with the engine. If holds vacuum, after being on vacuum at least an hour, finish finding the problem at the low pressure switch harness. If you find the problem, you can charge the system but you still want a good low pressure switch on the system. pay close attention to the high and low readings on the gauges. Look at a you tube video or two about what to expect. The readings will be effected by the ambient temperature and the condition of the system. Check the condenser for any debris clogged in it. If you have the a/c on, you should have the electric fans turning at same time.

 

[project_x]

Thank you

 

[project_x]

Put the vacuum pump on it and check to see if it holds vacuum and while you are doing that trace the wires from the low pressure switch and check for problems. Apply 12 volts to the clutch to see if will engage. If you get it to engage, see if the compressor turns with the engine. If holds vacuum, after being on vacuum at least an hour, finish finding the problem at the low pressure switch harness. If you find the problem, you can charge the system but you still want a good low pressure switch on the system. pay close attention to the high and low readings on the gauges. Look at a you tube video or two about what to expect. The readings will be effected by the ambient temperature and the condition of the system. Check the condenser for any debris clogged in it. If you have the a/c on, you should have the electric fans turning at same time.

When I find the problem and open the system (i'm assuming it might be open already...) should I replace the dryer?

 

[OR VietVet]

IMO, on these systems, any time you open the system, you should replace the accumulator/drier, the orifice and flush it. If the accumulator is relatively new, make sure you leave on a vacuum for at least an hour.

 

[project_x]

That's what I thought... I have not idea when anything was done... but figured it would be prudent to switch them.

 

[OR VietVet]

That's what I thought... I have not idea when anything was done... but figured it would be prudent to switch them.

And flush it. That means opening up the lines and flushing out wherever refrigerant travels. Have plenty of seals on hand.

 

[project_x]

And flush it. That means opening up the lines and flushing out wherever refrigerant travels. Have plenty of seals on hand.

I verified my compressor clutch engaged.
I'm putting a vacuum on the system.. if it doesn't hold vacuum what is the method used to find the leak? I see lots of ways to find the leak with systems with refrigerant...but not empty ones

 

[OR VietVet]

If empty and leaking, then you inspect every seal junction. Look for wet oily stains where refrigerant oil came out with leak when did have refrigerant in it. Or charge it and use a leak detector.

 

[project_x]

If empty and leaking, then you inspect every seal junction. Look for wet oily stains where refrigerant oil came out with leak when did have refrigerant in it. Or charge it and use a leak detector.

How long should i leave it holding vacuum to think there is no leak? I kept a vacuum on for 2 hours..and now the system is sealed and under vacuum... waiting to see if it leaks