Tom M'Guinn

Are you sure your gauge set is air tight? My cheap harbor freight gauge set won't hold a vacuum....

Dan Martinic

Hmm.. I bought an cheap one too.. and I remember you said that in your notes lol. It does hold 70 psi though (?) but I'm not sure if that's "easier" to hold than vacuum?

I guess I'll have to take a chance and get someone to come fill it. Too bad we can't buy 134a cans here. All we have is that hydrocarbon 12a stuff...

Dan Martinic

Almost forgot: the Hong Kong compressor doesn't have the two threaded ears on top; it only has one--the one for the M10 bolt. The smaller M8 bolt can't be used. The compressor does have the bottom two ears, but if you install the manifold properly with the S side the connections end, with the shape and length of the AC hoses you can't use the bottom ears.

So.. my compressor is held by the M10 on top and the adjustment turnbuckle on bottom, both at one end only!

Spring44

Someone correct me if I'm wrong but decades ago, when I was studying refrigeration in the Army, they always said that it was sometimes hard to hold a vacuum for a long time in a system that was designed to hold pressure. An ac system is designed to operate under pressure, not a vacuum.

The only reason that you pull the vacuum at all is to lower the boiling point of water in the system down to ambient temps so that it will vaporize and, along with the air, be drawn off by the vacuum pump. The rest of its life, the system is operating under pressure.

So, it seems that if your system holds pressure at this point, maybe you should just draw it down with the vacuum pump, add some leak-detection dye and charge the system with refrigerant. If it holds pressure, then you're done. If there is a leak, you can spot it from the dye and know what to fix.

Alternately, you could just take to a pro and let him check it with his equipment, charge it and have the peace of mind that would bring.

Dan Martinic

After calling a couple of these "we come to you" R134a-fill guys, I realized pretty quick that the $70 is labour only to come out; added to that is cost of R134a (both guys I called are asking $40 for that) and $80 per hour.. minimum 1 hour. So, here I am with gauges, vacuum, new compressor, and a system that may or may not be leak free, and I have to spend a minimum of about $200 just to see what happens.

For the three days of hot and humid, forget it. I went and bought what our country deems is DIY: 2 cans of propane (12a). Each can is 6oz and by a chart is says 3-to-1 vs R134a. So, if you need 30oz of R134a, you put 10oz of 12a.

While I was gone to the store, I shut the vacuum off. It had been running for well over 2 hours. This time, I took it out of the equation, making sure the gauges were closed, and low and behold I only lost a little bit of vacuum over about an hour (from 30inhg to 20inhg).

I did my best to put in 10oz of 12a. It's very difficult to weigh: I can't disconnect a not-empty can to weigh it. I used a kitchen scale to estimate the weight of the second can while still connected to my gauges. With an outside temp of 25 deg C and normal humidity, I ended up with 35-40 psi low side & 150-175 high side. Blows cold. Good enough!

Very curious how long this will last

Dan Martinic

PS.. I'd love to know why Porsche put the low side connection on the bottom... taking it to a shop means having them raise the car, remove the cover, remove the driver's wheel, remove the alternator air duct, then replace all that, and most won't let you watch or near the floor so it's behind closed doors.

Charlie

I would recommend isolating the condenser first. Around 20 years ago one of my 944's had a leak. I plugged one line of the condenser and used my vacuum pump to pull a vacuum on the other line. The pressure would not hold. I bought a new condenser and pulled a vacuum to -20psi and left it for several hours and the pressure did not change. Seems as if I used an old expansion valve to hook the line up to the pump but that was many years ago.