Model: 124 Spider
Engine Size: 2000
Refrigerant Type: R134a
Ambient Temp: 78F
Pressure Low: 40
Pressure High: 180
Country of Origin: United States
I replaced the compressor the other day on my custom built A/C system. The previous compressor leaked after swapping heads. I don't think I'll ever tear into a compressor again. Not like I would a turbocharger.
Anyway I asked an AC tech about charging the system for me and he was like "If you can put together a custom A/C system I'll tell you how to charge it yourself", so he gave me some tips. He didn't know about the volume either so he said try pulling a vacuum and see if it wlll hold for 30 minutes and add two 12 oz cans and see what happens. He said the least amount he has ever put into a system is 24 oz or as he said pounds.
I added a can and the temperature coming out of the vents eventually dropped to around 50F. Unlike with my previous attempt I started out with 70 PSI right off the bat. This time the pressure started out low and increased as I added more refrigerant.
Pressures were 45 on the low side and 180 on the high side. I added a second can but no change in the pressures or temperature. So I quit after 2 cans. But the temperature dropped an additional 5 to 10F (40 to 45F) while driving down the road. I have the radiator fan relay wired up so the fan kicks on when the compressor does but I suppose the greater volume of air going through the condenser helps it more than I thought it would.
In order to read both the high and low sides I connected my manifold guage to the high side but used the trigger type connector with gauge for the low side. Otherwise the hoses wouldn't reach both ports at the same time.
I shut the engine off and the static pressures are 65 PSI on the low side and 145 on the high side.
So between the engine running and not running there is a 5 lb difference between the two.
My only complaint is the evaporator unit is under the glove box so I have to aim the vents toward me but the fan does not produce enough volume of air to hit my face. I'm concerned my wife is going to get too cold because the unit is in front of her. But it seems to drop the temperature to a comfortable level even if the cold air is not hitting my body.
So what do you guys think about the pressure readings?
Here's some pics of my system.
Yeah we took my father's 98 Chevy van to the beach last week and we were in a constant battle with the thermostat.
I'm going to get one of those three guage pods that mounts on the windshield pillar and cut them apart and see if they will cover the vents and aim the air directly toward me. Except for the one vent next to the door.
The curvature of the evaporator unit is made so I think they will work using some 3M adhesive tape.
My wife grew up in Canada. We live in Las Vegas. Know what I hear in July?
"We are taking your truck? Let me go get a sweater."
Just the way it is. If the turbo is working right, she will be more worried about the road than the cold air...
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Quote:"I shut the engine off and the static pressures are 65 PSI on the low side and 145 on the high side"
That should not be. The pressure throughout the whole system should equalize. With R12, the resting pressure was close to the temperature in F.
Did it eventually equalize, or did you just measure immediately after shutting it down? I think that the low should be lower than it is when running, and the high, a little higher also.
simplificate and add lightness
I left the hoses connected for about 15 minutes after I shut the engine off before disconnecting the hoses. These are all new components so if the pressures did not equalize what would this be an indication of?
Sorry, I didn't see that you had a TXV. I just read that some will hold the pressure, so consider ignoring my comment...
simplificate and add lightness
I'm considering doing an ac system myself. Did your car have ac before? If no, what did you pull the system out of?
No this is a custom home built system. The evaporator unit I got off Ebay. Mainly because it was the largest unit I could find that would actually fit. The compressor bracket is for a FIAT twin cam engine but I modified it for a 505 compressor. I think the original dealer add on systems used a 508. This compressor wouldn't fit because of my custom turbo system.
I tried swapping heads off the 505 to go to a vertical port style but after I put the compressor on the car it leaked and I had 70 PSI on the low side. So I ordered a new 505 compressor. The condensor is a 12X20 I got from Nostalgic air. I had to custom cut all the hoses and make my own brackets.
So far after a month, the system is still working great. It's blowing 45F air out of the vents but the car's poor insulation is a factor. Also I have the vents aimed at me but can't really feel any air flow. So air just recirculates through the cabin.
I taped some bubble foam type insulation to the roof between the bows. I measued the temperature of the roof the other day. At 88F the insulated portion was around 95F. The uninsulated portion measured 140F!!!
Looks like crap for the moment but I need a new top and I'm hoping an upholstry shop can sew me a liner over top of this stuff when they install a new top.
No pics of the insulation but here's some more pics of the system:
You might want to consider the foil faced sheets, perforated, that are sold as radiant heat blocking insulation at the big box home repair stores. You could attach them to the underside of the top temporarily to see the effect. It will truly block infrared heat and weighs close to nothing. I have it installed in a room over the garage, and do not have the standard 'hotter than the rest of the house' feeling because of the radiant heat being blocked.
I would also suggest aluminum foil tape on the exterior of the evaporator case and on the lines to reflect exhuast radiant heat. I put it on the evaporator case when I put A/C into my Ranger. The exhaust manifold is about 2 inches from the case... well maybe more, but its close enough and I had the tape already.
simplificate and add lightness
Edited: Sun June 26, 2011 at 12:48 PM by tomw
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