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Old 03-04-2017, 05:15 PM   #1
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1974 20' Argosy 20
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Dash A/C rebuilding tips needed

In the near future I've got two Argosies that need the dash A/C installation completed and I'm looking for advice on how to go about finishing up the installation

On my Argosy I will be done with the hose installation next weekend at which point I will install Peanut's hoses.

A) Both have new compressors, both of which came with the manufacturers recommended amount of oil.

B) Both systems have all new components with the exception of Peanut's evaporator which is original and untouched. My evaporator has been cleaned by a radiator shop.

This is the first time I've dealt with a totally new and empty A/C system so I have some questions on what steps to take next once the hoses are installed. I know one of the next steps is to draw a vacuum on the system and I've got a good vacuum pump to perform that task.

The first question is since the compressors have been pre filled with oil won't pulling a vaccum suck that oil out?

If so then why do manufacturers send the compressors with oil? If not please explain why not!

Assuming it's acceptable to just go ahead and pull the vacuum how long should I vacuum the system and (assuming everythings tight) how long should the system hold the vacuum once the pump is off?

Assuming it holds a vacuum for X amount of time is this the point where you actually charge the system with freon and oil?

Thanks!

Brad
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Old 03-04-2017, 10:30 PM   #2
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Brad when you draw a vacuum you won't pump oil unless the hose connections are below the oil level which they shouldn't be.

The function of drawing a vacuum is to pull the air out of the system and more importantly to remove all moisture from the system. The vacuum lowers the boiling point of water so you must use a proper refrigeration vacuum pump as the cheap units will not draw a deep enough vacuum. This is more important in colder ambient temperatures. Warming the system helps the process.

How long the system has been open and exposed to humidity effects how much moisture may have entered the system. I have built a couple of custom refrigeration systems on boats. Using new tubing just the cutting, fitting and soldering time, I ran my pump for 24 hrs. just to make sure everything was dry. Btw I paid $400 for my pump about 35 years ago. It also requires an oil change on the pump for every use as the vacuum pump oil will absorb moisture and lesson pump efficiency.

Once you are ready to shut off the pump close the valves on your manifold set and the system should hold the vacuum indefinitely but if it holds for several hours it should be good. I realize most auto shops don't operate to these standards but I tend to operate with a bit of overkill and I don't like having to redo a job.

Next attach your refrigerant supply to your manifold set, purge the supply hose to the manifold and open both valves. Allow the vacuum to draw the refrigerant into the system until the flow stops. You need some refrigerant to activate the low pressure switch so the compressor clutch will engage. Close the high pressure side valve and start the engine with the A/C on high and charge the system through the suction side or low pressure side of the manifold. Fill the amount of refrigerant required for the system and if all the components are good and installed properly you will be blowing cold air.
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Old 03-05-2017, 05:56 AM   #3
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Dan, this is the info I was looking for!

So as I understand it, for the two hoses (suction & pressure) at the pump as long as they are above the pump there will be no issues with oil being sucked out of the pump while vacuuming. The fittings I bought for the pump have the hose fitting at the top pointing up. The hose fittings are 90s which places the hose another 1-1/2" above the pump.

The vacuum pump that I have is supposed to be a heavy duty pump rated for continuous use. We'll see if that's true

Thanks again!

Brad
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Old 03-05-2017, 10:53 AM   #4
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Brad it's where the hoses attach to the compressor. As long as they are above the oil level in the compressor. Basically if the oil doesn't run out of the compressor with the hoses disconnected the vacuum pump won't lift it. You would need to have a dip in the hose full of oil and the charging port submerged in the oil and the it would only pump the oil in the dip until it was below the point air could enter, kind of like air entering a siphon.
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Old 03-05-2017, 12:32 PM   #5
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Dan, thanks for the clarification. Sounds like my howe configuration will work out just fine.

Brad
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Old 03-05-2017, 04:06 PM   #6
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Anytime Brad. There are a few little details here and there but on the whole the process is straight forward. The important thing is the system wants to be clean and dry and of coarse sealed.
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Old 03-05-2017, 06:55 PM   #7
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I forgot to mention you want to charge the system as a gas not a liquid, the refrigerant can right-side up. If you want to speed the process a bit warm the can, hold it or put it in a bucket of warm water.
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Old 03-06-2017, 05:34 AM   #8
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Quote:
Originally Posted by Smartstream View Post
I forgot to mention you want to charge the system as a gas not a liquid, the refrigerant can right-side up. If you want to speed the process a bit warm the can, hold it or put it in a bucket of warm water.
Now this one I remember from when i had to recharge an hold Honda!

Thanks!
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