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Intro & Question

MikeC5 on Sun July 19, 2009 11:12 PM User is offlineView users profile

Year: 95
Make: Subaru
Model: Legacy
Engine Size: 1.8
Refrigerant Type: R134a
Country of Origin: United States

Hello, I'm Mike, new to the forum and new to doing auto A/C. I used to fiddle with older R-12 systems years ago when you simply added freon until the bubbles went away in the high side sight glass. Reading up on R134a it seems it's no longer that easy. So I bought a (cheapie) gage set and have been practicing with it. It all seems to make good sense excpet that I'm a little confused on just how the quick disconnect fittings (with valve) are intended to work.
The gage instructions say the valve on both low and hi fittings should be closed (CW) until all is hooked up tot he car and then open both valves to get the pressure readings. So far so good. In order to add freon, everything is the same except now the low side manifold valve is opened to let freon flow into the system. When I first tried it, the low side gage quickly went up to 90 psi and sat there. No freon appeared to be flowing (manifold site glass). A bit of head scratching - the valve at the QD fitting is open (full CCW) so what gives? I close the low side manifold valve and pull off the QD fitting and look at it closer. It seems that when the thing is in the 'closed' position (full CW), it will be pushing the schrader valve open more than when it is full CCW. I suspect at full CCW it was not opening the schrader valve at all. Is this just what is to be expected with a cheapie gage set or did I miss something? Also, if I set this valve somewhere between open and closed, I then read normal pressure on the low side (approx 30 psi). Does anyone have a cross section that shows what the inside of the QD/valves look like?

Chick on Mon July 20, 2009 6:28 AM User is offlineView users profile

Your instructions appear to be wrong. You ccw the couplers to connect, then turn them cw to depress the shrader valves.. You always keep the wheels on the manifold closed except the low side when charging. NEVER open the high side wheel while the car is running and the AC is on, you can blow up the can. The high side wheel should only be open when pulling your vacuum or a couple other reasons which you are not ready for yet.. So keep that wheel just the couplers once connected... Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

GM Tech on Mon July 20, 2009 8:29 AM User is offline

You don't use the sight glass in the manifold gage set for anything other than observing refrigerant going in or out of the system during a recovery or recharge--the gage set valves need to be closed during system operation- otherwise you are bypassing the cars system- don't try to do the "bubbles cleared" charging method- it is not like a sightglass on a car that you are used to....

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......

MikeC5 on Mon July 20, 2009 10:18 PM User is offlineView users profile

Thanks for the replies guys. I really do think the instructions are wrong. Probably due to poor translation.... I thought I would try testing it with compressed air but I see there is a collar/ring in there that appears to be depressed by the tip of the service port. I believe this is what opens the valve itself and the knob simply moves the schrader valve pusher in and out. I'll have to get a spare low service port fitting to test this theory out though.

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