Recharging system

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wattalife54
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Joined: Sun Feb 10, 2019 3:45 pm

Recharging system

Postby wattalife54 » Sun Feb 10, 2019 3:54 pm

I replaced the compresser and drier on a class A diesel pusher motor home. The system has not been used for ten years. Following a good vacuum result do I need to add any oil or just add the R-134A.

Thanks,
Bob
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bohica2xo
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Re: Recharging system

Postby bohica2xo » Sun Feb 10, 2019 4:29 pm

Was the new compressor shipped dry? Or full of oil?

With 10 years out of service there must have been a reason. Gross leak? Dead compressor?

How much oil was in the old dryer? That is a big clue about lube in Class A pushers. Always drill & drain them when replacing one.
wattalife54
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Joined: Sun Feb 10, 2019 3:45 pm

Re: Recharging system

Postby wattalife54 » Mon Feb 11, 2019 9:45 am

The compressor was filled with oil. Just did not need/use the dash air for 10 years. Have not replaced the dryer yet, but will before putting the system back in service.
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bohica2xo
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Re: Recharging system

Postby bohica2xo » Mon Feb 11, 2019 11:17 am

When you remove the old dryer, lay it flat & drill a small hole in the bottom corner of it A 1/8" hole is plenty.

Then prop it up over a measuring cup, and let it drain overnight to see how much oil was in the dryer.

If no oil comes out the system was not returning oil very well, and you should add 2 ounces of oil to the new dryer before installing. If you get less than 2 ounces out, put at least 2 ounces back. If you get more than 2 ounces out, put the same volume recovered back in to the new dryer.

Class A pushers all have different oil balance requirements depending on the plumbing routing. The oil has a long way to go in the suction line to get back to the compressor.
wattalife54
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Joined: Sun Feb 10, 2019 3:45 pm

Re: Recharging system

Postby wattalife54 » Wed Feb 13, 2019 12:34 pm

The drier is empty.
The coach manufacturer states to add 1 oz PAG 10 or 20 for every 10' of coach length, if the system lost it's charge completely due to severe leaks. (broken comp. discharge header) This is in addition to the oil(PAG 150) in the compressor. In my case that would be 4 oz. Can I add the oil to the drier anywhere or through a specific port. Is the PAG10 or 20 outdated technology? Should I use PAG 150 instead?

Thanks,
Bob
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bohica2xo
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Re: Recharging system

Postby bohica2xo » Wed Feb 13, 2019 1:10 pm

So it DID have a Gross Leak. Why would you withhold information like that? AND it has been open to the environment for 10 years.

So the PAG that is in the system has been soaking up water for a decade. Did you flush the entire system before you closed it up?

There is no PAG 10 or 20. There are SP10 & SP20 PAG oils, which are Sanden oil designations. Both are lower viscosity than PAG 150, and the last thing you want on a pusher is thick oil. SP10 oil would be my choice. SP10 is equal to PAG46 for viscosity.
wattalife54
Posts: 4
Joined: Sun Feb 10, 2019 3:45 pm

Re: Recharging system

Postby wattalife54 » Wed Feb 13, 2019 1:32 pm

I found the break recently. As I am always doing something on the coach I am certain it has not been very long. When I bought the coach the system did not cool. I have decided to restore it as I will now be using the coach in conditions that will require use of the defroster. Do you recommend flushing the system and is there information on what to use and how to do it?

Thanks,
Bob
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bohica2xo
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Re: Recharging system

Postby bohica2xo » Fri Feb 15, 2019 10:44 am

If the system was inoperative when you got the coach, it likely had a smaller crack that had released the refrigerant.

Hopefully the previous owner did not try any "Magic in a Can" sealer products in the system.

This message board was rebuilt when the software for the old one became obsolete. We have an archive of old threads, and this one you should review because it contains good posts & pictures that relate to your coach:

https://autoacforum.com/messageview.cfm?catid=2&threadid=20705

We also have a forum dedicated to flushing questions:
https://autoacforum.com/viewforum.php?f=5

Basically you need to flush any MVAC system by breaking the system down to individual parts & flushing them one at a time.
A solvent that dries completely should be used, and you need to get it ALL out. Back to bare metal or rubber on the inside of things. It can take a lot of dry air to blow out a 30 foot line properly.

Since the dryer was empty, cut it open & see what it looks like. Break some connections & look at the inside of the plumbing.

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