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Hot Expansion Valve

bkeese on Fri June 19, 2009 7:01 PM User is offline

Year: 1984
Make: VW
Model: Vanagon
Engine Size: 1.9
Refrigerant Type: R-12
Ambient Temp: 100
Pressure Low: 55
Pressure High: 250
Country of Origin: United States

Please help a newbie with what I hope is a basic problem. I have just finished flushing and evacuating the system on this van. I had it the vacuum on it for about three hours, then I let it sit for an hour to see if it would hold a vacuum. It did. Then I charged the system with about 36 ounces of R-12. It is supposed to hold about 50 ounces at full charge, but I stopped adding when I saw the readings on the gauges. I let it sit and run for a few minutes to see what would happen. The readings stabilized about 55 & 250. I started reading my HVAC manual and wasn't able to find an explanation that was convincing to me. One that surprised me was the the liquid side of the expansion valve was hot, almost too hot to touch. The vapor side was cold, but not icy. The fan on the condenser was operating fine, and the vehicle's temp was normal.

I'd appreciate any help.

Brian

Chick on Fri June 19, 2009 7:35 PM User is offlineView users profile

You need the full charge in the system.. You're about 14 ounces low, add it slowly and just watch the high side.. wet the condenser if need be.. Do you have a high pressure cut out switch? are you sure there isn't any air in the system/

Also are you using virgin R12 or something that "12' in it's name???

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Edited: Fri June 19, 2009 at 7:36 PM by Chick

bkeese on Fri June 19, 2009 7:49 PM User is offline

Thanks for the input. I'll try wetting the condenser to see what affect that has. I'll have to check my diagrams to see about the high pressure switch, but the compressor never did cycle off. I don't think there could be any air in the system; I went straight from deep vacuum to putting in the refrigerant. Virgin R-12 in 12oz cans.

Edited: Fri June 19, 2009 at 7:49 PM by bkeese

Chick on Fri June 19, 2009 8:23 PM User is offlineView users profile

at 100 degrees, I doubt it would cycle.. the hotter it is the less cycling, and expansion valve systems rarely cycle anyway.. But running it low of refrigerant is not good....

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

JJM on Fri June 19, 2009 8:31 PM User is offline

At 100F ambient, I wouldn't expect anything other than a hot TXV inlet.

I agree with Chick (as always) you do need a full charge in the system. I'm probably in the minority here though about high side pressures, as I typically only get concerned north of 350 PSI when your dealing with high ambient temps.

What concerns me, however, is that 55 PSI reading on the low side. Were those readings at idle or at 1,500 RPM or higher? If at idle, they're probably OK, but if at 1,500+ then I'm a little concerned, and you might want to do some testing on the TXV before dumping more $$$ R-12 in the system.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com



bkeese on Sat June 20, 2009 9:28 AM User is offline

Well you called it. Everything was fine. I somehow missed the significance of the engine rpm. Keeping it at 1500 brought things down into range. It's now fully charged and working just fine. Now I can deal with those ambient temps: I'll just stay inside the van!

Thanks everyone so much!

Brian

Edited: Sat June 20, 2009 at 9:31 AM by bkeese

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