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Discussion Starter #1
Well I replaced the broken AC line that goes through the firewall, and want to evacuate the system before I recharge. Does anyone have a write up on how to do this?
I have a manifold and a vacuum pump, I am just not sure how to do it. IE how long to you keep it under a vacuum, and do you just evacuate the low side, the hi side, or both.

Thanks
 

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DakotaTacoma said:
Well I replaced the broken AC line that goes through the firewall, and want to evacuate the system before I recharge. Does anyone have a write up on how to do this?
I have a manifold and a vacuum pump, I am just not sure how to do it. IE how long to you keep it under a vacuum, and do you just evacuate the low side, the hi side, or both.

Thanks
honestly....you did hte expensive part of the job replacing the line...jsut take it to a shop and have them evac and recharge.....they have the proper machine to do it and it doesnt cost that much and you will know its done right....but most of all it will be done WAAAY faster
 

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Discussion Starter #4
Found a good write up on evacuating and recharging an AC system, it's for a Chrysler Imperial with a R-12 system, but the general procedure is still the same.

Once re-assembled, connect the manifold to the system and the vacuum pump to the manifold. (Blue hose to the valve connection on the back of the compressor [low pressure side]. Red hose to the valve connection on the muffler in-line with the connection on the front of the compressor [high pressure side. Red = danger]. Yellow hose to the pump. Open both valves.) Pull at least 28" for at least 60 minutes. More vacuum for longer is better, since it removes more moisture. Moisture combines with the refrigerant and forms acids. I had to replace the H-valve in my 83 Imperial because Chrysler did not properly evacuate the system, and the insides of the aluminum H-valve corroded and plugged the liquid passage.
Close both valves and turn off the pump. (In that order) Watch the vacuum gauge for 20-30 minutes. If the pressure rises, you have a leak.
Find that leak. To find the leak either: 1) coat fitting with refrigerant oil and see if the leaking stops. 2) Charge to 70 PSI with dry nitrogen and check for leaks with the leak detector solution.
Now you are ready to charge. If you can get refrigerant, connect the yellow hose to you supply, and turn on the tank valve. Slightly loosen the yellow hose's connection at the manifold to let a little gas escape.
This purges the air and moisture from the yellow hose. Retighten the connection. R-12 charges as a gas. Most R-12 substitutes charge as a liquid. Check the instructions for the product you are using.
Weigh your tank. If you are using small cans, I think 3 cans is the exactly correct amount for single unit systems.
If charging as a gas:
Hold the tank upright (usually marked "This end up for GAS." Open the blue hose valve and let the gas flow until it stops. (Gauge should read close to 70-75 PSI.)
Start the engine, A/C on and set to HIGH. Adjust the blue hoses valve so that the charging pressure is no more than 80 PSI. Charge until the correct amount is pulled into the system. (Check the weight of the tank.)
If charging as a liquid:
Hold the tank inverted (usually marked "This end up for LIQUID." Open the red hose valve and let the liquid flow until it stops.
Check gauge pressure. Close red hose valve. Start engine, A/C on and set to HIGH. Adjust blue hose valve open to increase suction side pressure by usually no more than 10 PSI. (The idea is to slowly draw liquid from the tank, but for it to vaporize while it is in the blue hose, so that no liquid hits the compressor, where bad things happen when liquid refrigerant enters.) Oh! You want to pull liquid from the tank because the substitutes are usually mixtures with different boiling point. Pulling liquid pulls them all in equal proportions. Pulling gas pulls mostly the one with the lowest boiling point, then the next when the first is gone, then then next, and so forth. Not what you want to do. Stop charging when the appropriate amount (by weight) is pulled in.
Close all valves. Stop A/C and engine. Remove hoses. Here's a little hose removal tip from some who learned the hard way. Hold the metal tube of the hose end in against the fitting while you unscrew the connector.
Once the connector is completely unscrewed, pop the tube off. If you don't do it this way, you usually get quite a lot of leakage while disconnecting the hoses. On the high side, that mean oil and liquid refrigerant spray out.
Cap the valve ports.
Enjoy the coolness.
http://www.imperialclub.com/Repair/Air/general.htm
 
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