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A/C Vacuum Question

butcher321 on Thu July 02, 2015 10:41 AM User is offlineView users profile

Year: 2000
Make: Chevrolet
Model: S10 LS Pickup
Engine Size: 4.3L
Refrigerant Type: R134a

Bought this truck last November. Only has 64,500 miles and mechanically runs great. However when I went to use air this summer it blew hot. Hooked up manifold gauges and the read 10 psi static. Charged with 2 small cans (no death kits) and put in some UV dye. Blew nice cold air. When I put the light on it there was a leak at lower condenser connection and spots of dye on front of compressor. Compressor ran nice and quiet. Had system evacuated and replaced the compressor, accumulator/dryer, hoses and orifice tube. When I pulled the old orifice tube it looked pretty good, could not see any metal particles. Next I put a vacuum pump and let it run for an hour. However I am only getting a reading of -16. I did let it set overnight and still read -16 in the morning. Question is: Why would I only be getting a -16 reading. To me its does not appear to be leaking as gauge did not move overnight. Due to be retired and on limited income I am using Harbor Freight gauges and pump. Pump is 2.5 cfm, single stage, 1/6 hp motor.

butcher321 on Thu July 02, 2015 12:49 PM User is offlineView users profile

Does this sound like bad manifold gauges?

Dougflas on Thu July 02, 2015 2:22 PM User is offline

Why did you replace the compressor? You stated it ran nice and quiet. You may have a leak at your manifols thus not pulling a full vacuum. You will need to test the pump, hoses, and manifold.

GM Tech on Thu July 02, 2015 4:17 PM User is offline

pull a vacuum on the gage set only- not hooked to truck-- this will test your gage calibration.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

butcher321 on Thu July 02, 2015 6:13 PM User is offlineView users profile

1. Replaced compressor because it was leaking R134a. Did not want to wait until it tanked and got junk all through the system.

Tried pulling vacuum with just gauges and gauges kept vibrating between 0 and -10. So I Rechecked all hose connection and made sure they were snugged down tight. Hooked hoses back up to truck to see if it pulled vacuum to -16 again. I am pleased to say that it now shows -28. Waiting now to see if it leaks.

Edited: Thu July 02, 2015 at 6:19 PM by butcher321

butcher321 on Thu July 02, 2015 9:24 PM User is offlineView users profile

Ran the pump for an hour showing -28. Shut pump down and waited an hour and it still showed -28. Tomorrow will put radiator back in and then charge her up!

butcher321 on Sun July 05, 2015 3:52 PM User is offlineView users profile

Well due problems putting radiator in and then holiday weekend did not get to charge till this am. Pleased to say that I was able to get low and high pressures according to GM service manual and center vent temp of 46 deg is also what service manual said I should get.

Edited: Sun July 05, 2015 at 3:55 PM by butcher321

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