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Questions about reviving A/C

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Galant VR-4 org Post #: 1245809 posted 04/12/19 01:36 PM     Remind Me!  Send Private Message   Edit Post      
398 does not have operational AC, although it did before I did the engine swap. The lines were left open and so I know the dryer is f'ed, and I plan on replacing the expansion valve. I'm refilling the system with R12. These are my questions:

Is there a drain plug? I'd like to replace the oil (every 27 years seems appropriate), and I'd prefer to not pull out the compressor if possible.
How hard is the expansion valve to get to? I know you can get to it via the glove box and I've read the FSM... maybe I'm making a bigger deal out of it than it is, but it isn't making sense to me.
Does oil only go in the compressor? I read somewhere that 2/3 goes in the compressor, and 1/3 goes somewhere else, I don't recall. I'm inclined to put it all in the compressor, but just checking.


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iceman69510 Galant Moderator
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Galant VR-4 org Post #: 1245832 posted 04/15/19 09:24 AM     Remind Me!  Send Private Message   Edit Post      
When the system is built and originally filled, all the oil is in the compressor. When you replace any component, it is generally assumed that some oil stays in each area of the system, thus you only replace the amount of oil calculated to be in the component being replaced.

There is no drain plug. If you do a full flush of the system and then vacuum it, you can put the specified amount only in the compressor.

When I revived the AC in my 94 about 8 years ago, I replace the o rings on all the connections, replaced the dryer too. Did not flush it, but did add a small amount of oil (don't recall how much) and then did evac and fill with R12. Turned out great and was nice and cold.

I am not sure about the expansion valve question, as I have not done that.

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Galant VR-4 org Post #: 1245844 posted 04/15/19 08:58 PM     Remind Me!  Send Private Message   Edit Post      
The expansion valve was relatively painless. After disconnecting the hard A/C lines from under the hood, its just two 12mm bolts on top of the evaporator, and a 12mm nut underneath. The hardest part for me was finding the stupid evap plate, which is piece of plastic that slides up and down to unlock a notch in order to get the evap out from behind the dash. It's 1-1.5 inches to the left of the vertical electrical connectors. The rest is fairly straight forward.

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Galant VR-4 org Post #: 1245887 posted 04/19/19 08:46 PM     Remind Me!  Send Private Message   Edit Post      
I got the relieve valve on the AC compressor replaced, part number MT1611 from Autozone. It's a two piece with green o rings. At the bottom of my compressor toward the back(near the relief valve), I found three bolts with 10mm heads and o rings. I'm guess this is for oil/freon? But no oil came out. Not sure what that means; maybe all my oil ran out already. So know I'm just waiting for my freon.

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FlyingEagle Galant Moderator
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Galant VR-4 org Post #: 1245892 posted 04/20/19 12:04 PM     Remind Me!  Send Private Message   Edit Post      
Iceman hit the nail on the head, with regards to system upkeep and parts changes that relate to oil.

If you get the system flushed with a machine, the owner/operator should be well versed on how much is going through and or back into the system.
From that point make sure he has the spec for total system capacity and the capacity for compressor replacement.

The relief valve opens when the system pretty much dead heads, like when you cover the condenser with cardboard and the system pressures skyrocket as heat cannot escape through the condenser side of things. It will usually relieve someone north of 350-400psi iirc.

If you have never had the compressor off the car and or it was never filled and checked for system operation during your ownership, it would be best to take it down and completely drain it, and refill it.

If you do remove it and you can catch all the fluid (if the proper amount is going to come out anyways) use a graduated container with 10 ml graduated markings, to say the least.

If the oil removed matches the spec, replace with same amount of oil - fresh.
If the oil removed does not match the spec, IE under - you lost some during processes or it was low to begin with.

Oil should not be in excess in the remainder of the system, because the bulk stays on the compressor and the "mist" is what makes its way around the system during activity - normal and expected but too much due to over fill will cause issues with efficiency.

When you have a sealed and operational system. simply putting the recovery machine into action and performing a complete draw down in the system, can leave you with some decent amounts of oil removed - this has not been the case for you yet, that you know of.
That oil during regular service must be matched and returned to the system (fresh), after vacuum is applied to boil out the moisture, and right before the refrigerant fill that will push the remaining oil in the lines that hasn't been totally sucked in by the system under "pull"/vacuum.

Ninja edit - How long was the system open for? Days? Weeks?

Replace the drier, and confirm the compressor oil capacity (via draining while rotating clockwise on the clutch assembly with the compressor out of the car) you would be changing seals as a matter of course, and see what you come up with. I've seen many system open for days and or weeks and driers not changed and had them vacuumed for like 1+ hours, and they come back quite well, but yes, replacing the drier will guarantee low system moisture content and less chance of internal failure by contaminants.

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Edited by FlyingEagle (04/20/19 12:08 PM)

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Galant VR-4 org Post #: 1245907 posted 04/21/19 05:38 PM     Remind Me!  Send Private Message   Edit Post   
The system was open for . . . months? Maybe a month. For 13 dollars or whatever I paid for the dryer it's well worth it. Part of my problem is that I did basically everything wrong. If there is an AC mistake, I think I made it. The good news (if I can be generous) is that I only operated it incorrectly for a little bit.

My neighbor is a retired engineer with an AC company, and he has graciously offered to lead me to the way of righteousness and goodness. The relief valve has spread it's goodness all over my driveway, his driveway, and probably a little on the 33 highway north of Ojai. I can guarantee that what is left in the compressor is well shy of spec. He found the specs for amount of R12 and mineral oil. High pressure side was on the high end of normal, low pressure side was half of what it should be, so he suspected a restriction in the system. I suspect the drying is over saturated, but did the expansion valve to be on the safe side. On Monday, we will pull vacuum, replace the dryer, and put in the freon and oil (not in this order).

I'll let everyone know how things go.

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