Refurbing a Very Early A/C System

[DMC5180]

Are you sure your test lines depressed the service valves and your manifold gauge works? When I do something and doesn't seem to make sense I recheck what I did to make sure I didn't do anything wrong.

Back in post #3 it says the vacuum pulled down to 60hg quite quickly.

Btw, thats a cmHg scale. Normally it would be INHg
30-31 inhg would be normal full vacuum.

Which makes me think that the gauge valves might not be open.

[DMC-81]

Good work there Dana, keep it up

I'd recommend to soak any O rings in air con mineral oil overnight before fitting to aid sealing.

Thanks! I'll do that.

The puzzler here is that it didn't build system pressure. Because it is closed loop, any blockage/restriction should cause the Highside to climb like crazy.

Broken reed valves would cause no pressure to build. But from your teardown inspection all the components appear to be good.

Fwiw, when you reassemble the clutch, be sure the air gap is within spec.
.016"-.031". Adjust or remove shims as needed to bring into spec. When I was redoing my system last year, I noticed the clutch was slipping intermittently. The Clutch Air gap was almost .060. Since I was replacing the compressor anyway with an SD7H15, it didn't matter to me. For comparison the New compressor's clutch was near the bottom of the spec.

Yeah, I expected a failed compressor or a plugged orfice tube, but I have yet to check the evaporator and condenser. Thanks for the air gap specs, I'll be sure to check it during assembly. I checked that during evaluation before disassembly and it was within spec.

Back in post #3 it says the vacuum pulled down to 60hg quite quickly.

Btw, thats a cmHg scale. Normally it would be INHg
30-31 inhg would be normal full vacuum.

Which makes me think that the gauge valves might not be open.

Correct, but I tested the system 3 times before teardown and the high side gauge:
- needed to be purged
- showed readings all 3 times (and some mild fluctuations)
- and went negative during vacuuming.
If either side was not connected, I would expect a zero reading, right?

Good discussion.

Regardless, I'm in the refurbishment process now, which I needed to do anyway to replace the seals, orifice tube and accumulator.

[DMC5180]

In case you didn't know this was an available resource.

Sanden SD AC Compressor Service Manual

https://r.tapatalk.com/shareLink?sha...3&share_type=t

[David T]

If you didn't depress the service valves and tried to pull a vacuum you would see a negative reading on your gauges. It would be the vacuum in the hoses right up to the service valves. You might think you have a vacuum going into the system but it only goes up the the cores of the service valves. It is possible the clip that depresses the cores is missing OR you put the hoses on the manifold on backwards and the clips are on the manifold side. One reason when I pull a vacuum I like to use a core extractor. That way I KNOW I am into the system and I have a much larger passageway into the system.

[DMC-81]

If you didn't depress the service valves and tried to pull a vacuum you would see a negative reading on your gauges. It would be the vacuum in the hoses right up to the service valves. You might think you have a vacuum going into the system but it only goes up the the cores of the service valves. It is possible the clip that depresses the cores is missing OR you put the hoses on the manifold on backwards and the clips are on the manifold side. One reason when I pull a vacuum I like to use a core extractor. That way I KNOW I am into the system and I have a much larger passageway into the system.

Good information. Makes sense. Although in my case, I'm pretty sure I pulled the vacuum right. I used new (tested) gauges that were demonstrated as being effective at depressing the service valves.

[DMC-81]

While waiting for a special tool for the compressor, I was finally able to remove the A/C Accumulator yesterday. I struggled to crack the evaporator to accumulator connection loose, mainly due to space and the angle. I have heard that you can access this fitting via the fuel tank access panel, however, for me, I found the heater and fuel hoses in the way. So this is the position that I was best able to reach it. After trying a special 1 1/16" crow's foot and angled combination wrench, the tool that accomplished the task was an adjustable wrench. Who knew!! I removed the bracket ring first but snugged up the bottom fitting again (which I had already loosened) to keep things as rigid as possible.

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I was very cautious to avoid bending the soft aluminum evaporator tubes. I used the the other 2 tools to gently work the #12 male o-ring fitting back. I also put the liquid line back on to help keep that evaporator tube as steady as possible.

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Success! Here are the tools that I used. 1 1/16" is the proper size wrench on the evaporator end and 1 1/4" on the accumulator side. Same sizes for the bottom tube to #12 suction hose. Although, I found that I didn't need the 1 1/4" wrench on the top fitting as I held the accumulator steady with my hand.

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I packaged it up and sent it away to Original Air in Tampa today for rebuilding. Fingers crossed!

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[DMC-81]

Today, I cleaned the small portion of the frame behind the accumulator.

Before:


After:


Early cars up to a certain VIN don't have a high pressure switch (or safety release valve), so, as part of my refurbishment of this system, I'm going to add them. First to be installed is the DMC high pressure switch wiring harness (110526). One end needs to go through the hole in the firewall. First, I threaded some spare wire that I had through the hole from the inside. Then I taped it to the harness. I put plastic around the connector to protect it from the the gooey cork tape.


I found that it was too tight to squeeze between the biggest space between the 2 evaporator tubes. Because the molex connector was the thing that got caught up, I carefully removed it and taped the harness to the spare wire that I had, then taped it up:


On this second attempt, it threaded through easily. Notice the connector with the jumper attached. This is where it connects on later cars. On my early car, the provision was there in the main harness, but it wasn't used.


After reinstalling the connector, I removed the factory jumper and plugged the harness in, threaded the extra harness back through to the outside, then zip tied it out of the way:


Now I have both low and high pressure connectors ready to go:

[DMC5180]

That is what I had to do when I replaced my Relocated my HP switch to the Outlet adapter on the lower condenser connection.

Btw, is that HP switch harness about 4 ft long? If so, it is intended to reach the HP switch at the condenser. The early version that used the Hub hose assembly that had the switch a few inches away from the accumulator was a much shorter harness.

[DMC-81]

That is what I had to do when I replaced my Relocated my HP switch to the Outlet adapter on the lower condenser connection.

Btw, is that HP switch harness about 4 ft long? If so, it is intended to reach the HP switch at the condenser. The early version that used the Hub hose assembly that had the switch a few inches away from the accumulator was a much shorter harness.

Cool, and thanks for letting me know about those 4 parts. Yes, this harness is about 4 feet long. I trial fitted it and it is long enough to follow the condenser/evaporator line (110525) and connect to the hub/adapter (110527).

[NckT]

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