Refurbing a Very Early A/C System

[DMC-81]

Great work, I'm enjoying reading this overhaul.

May I suggest that as soon as you connect the accumulator, as it also contains the drier silica gel, immediately pull a vacuum in to prevent the gel from absorbing moisture from the atmosphere/ moisture present by air in the refrigerant pipes.

Good luck with the project

Thanks! That is a great tip. I'll definitely do that.

[DMC-81]

Today, I began by cleaning the compressor brackets. I also blasted compressed air through the high pressure hose & condenser, and through the evaporator. The air passed through just fine. That was good news, as it indicates the entire system is free of any blockages.



Next, I began replacing the front seal (Santech MT2043 kit). It was highly recommended to use a special seal protector (Santech MT4024) to stretch the seal and protect it from being damaged by the threaded portion on the shaft when you install the front cover. The parts of the seal came out of the housing in the order pictured, first the felt ring, then the snap ring and the metal retainer/washer, then the O-ring and finally the carbon seal assembly. Once the snap ring was removed, I just tapped the retainer/washer out from the inside using a medium nail punch. It is only restricted from coming out by the tension on the O-ring, so it just needed a firm tap.


New seal parts laid out in order. Before I began installing it, I cleaned the bore area with an old toothbrush and mineral spirits, then blasted it with compressed air to make sure there was no debris:


Next, the carbon seal assembly went in with the metal end to the inside, then the green HNBR O-ring which was soaked in mineral oil. Then I applied extra oil to the O-ring and the bore using a clean artist's brush:


Next came the metal retainer/washer. I just lubed the edges with oil, then pushed it in place evenly using both thumbs. Then came the snap ring, beveled side up:


Finally, the felt ring is pressed into place. This seal package didn't come with a new one, so I soaked my old one in mineral spirits to clean it, let it dry for a couple days, and then re-used it. It came out just like new.

[DMC-81]

Well, it was time to re-install the Front Head Plate on the compressor. In this picture, I had the parts laid out to do the task: a seal kit from Santech ( MT2143 ), and the seal protector sleeve. Besides the large square cut head plate O-ring, the kit also contains the two gaskets for the rear cover/cylinder head, and a green HNBR O-ring for the oil fill plug.


Seal protector sleeve in place (and lubed) on the shaft, and the two sets of thrust bearings on both sides of the driver assembly, lubed with mineral oil and aligned:


New head plate O-ring in place with a little bit of mineral oil around it to prevent it from jumping out of its groove:


I carefully lowered the front seal through the seal protector, and aligned/positioned the front head plate and driver assembly. It is under a little bit of spring tension, so I started 4 bolts in each cornering, gently tightened them equally to draw the plate until it seated, making sure it didn't bind. Then I inserted and tightened all bolts similar to a head sequence. Then I torqued them to 23 inch pounds.
finally, I trial fitted the armature assembly so I could rotate the shaft to ensure free movement. It worked nice and smoothly.

[David T]

Since you are going through all of this trouble and the system is "open", before you put it all back together and close it up, the last thing you should do is run flush through the condenser and evaporator cores. That will remove any residue, old oil, and most moisture. Kind of getting the insides back to like new condition. Don't run the flush through the accumulator or the compressor. Hook them up last. Then immediately fill with Nitrogen to pressurize the system with dry gas so you can pressure test for leaks.

[DMC-81]

Since you are going through all of this trouble and the system is "open", before you put it all back together and close it up, the last thing you should do is run flush through the condenser and evaporator cores. That will remove any residue, old oil, and most moisture. Kind of getting the insides back to like new condition. Don't run the flush through the accumulator or the compressor. Hook them up last. Then immediately fill with Nitrogen to pressurize the system with dry gas so you can pressure test for leaks.

Thanks. Yes definitely, flushing is coming up soon. There was no oil in the compressor, so there's approximately 6 oz of old oil elsewhere that needs to be flushed. I checked on the accumulator today, and Original Air should be done rebuilding it by the 10th. It should arrive sealed and good as new. So definitely, I won't run flush through it.

Now, your advice to immediately fill with Nitrogen is contrary to what NickT said about immediately vacuuming it down to remove moist air.

So, should I do one and not the other, or both. If both, which one is first? I'm thinking an intitial vacuuming to remove moisture (while checking the gauges for any major leaks), and then pressurize with nitrogen to test for leaks. Then a final vacuum before recharge.

[Bitsyncmaster]

Dry Nitrogen would be fine to keep the unit dry until you recharge it. But it's mostly just used for pressure testing. Not many of us keep a tank of nitrogen around.

[David T]

It's a judgement call about the order. If yo have a big leak and you try to vacuum the system you are only drawing in more air and moisture. If it is cool and dry when you do it, it isn't a big deal. If you have clean, dry shop air you can pressure it to about 100 psi but an A/C shop (a GOOD shop) will have a bottle of Nitrogen and pressure test at 200 psi. Not uncommon. Good shops have the right tools and know how to use them. Just saying how it should be done, Different shops use different procedures (read short-cuts).

[DMC-81]

I refurbished the rear cover this weekend. Here is the head gasket removal in progress. I soaked the old fiber gasket in mineral spirits for a week, and then carefully scraped it off using a razor blade, and a dull putty knife, being very careful not to bend the reed valves. I angled the blades at a steep angle to avoid scratching the valve plate surface. I also used Goo Gone after the gasket was torn which dissolved it well.


Interior gasket removed:


Here is the outer gasket separated from the rear cover. I gently pried the plate off the cover:


To completely remove the gasket material from the valve plate, I first dissembled the valves and removed the 2 guide/roll pins, and then sprayed it liberally with Goo Gone and let it sit for a few minutes. Then I scraped it gently with a razor blade, then wet sanded it with 600 grit (with a block) and Goo Gone, followed by wet sanding with 1000 grit and mineral spirits:


Both sides of the valve plate clean and smooth, ready for re-assembling the valve assembly:


I reinstalled the guide pins, coated each part in mineral oil, aligned the valves on both sides, then hand tightened the nut:


Then I torqued the M6 nut to 36 inch pounds:


I used the same process described above to remove the gasket on the rear cover, this time using a longer blade across both sealing surfaces to maintain the flat surface of the thin aluminum material:


Rear cover clean. Here are the gasket kits, rear kit (Santech MT 2143) and a general HBNR O-ring kit (Santech MT 2547) or the DMC O-rings for the rear cover 100747:


Interior metal gasket coated with oil on both sides and placed:


Valve plate placed. I was careful with the orientation:


Outside metal gasket placed with oil on both sides:


Rear cover placed, and the M8 bolts hand tight:


Then, the five M8 bolts were progressively torqued to 26 ft/lbs and the ports temporarily blocked off:


Compressor rebuilt. I discovered that it was painted with an aluminum colored paint so I'll refresh that before reinstalling the clutch, pulley, and armature....:

[NckT]

Excellent

[DMC-81]

Just an update: To prep for painting, I wet sanded the compressor with 600 grit, cleaned and masked it. I also increased the torque for the 5 head bolts to from 26 to 29 ft/lbs:


Here is the compressor after spraying with 3 coats of VHT aluminum caliper paint:


I cleaned up the coil and the armature plate, and wrapped the coil wire around a screwdriver shaft to simulate the original winding:


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Excellent

Thanks!!