A/C re-installed - how much oil / R134a to add and should I change the compressor?

[82DMC12]

A few years back I replaced EVERYTHING in my A/C system except for the evaporator so I could switch to R134a and it's been working pretty well. I bought a kit from Hervey but supplied my own custom parallel flow condenser.

Now, I recently had to open my A/C system in order to do a frame-off. I replaced the accumulator but re-used everything else except for the green o-rings that were exposed to the air when I had various fittings apart. I installed new o-rings and smeared them and the threads with Nylog Blue.

I am waiting on some parts and it looks like I could be 3-4 weeks out of commission before I can bring the car in to get the A/C recharged.

This week I'm going to get one of those compressed-air powered venturi pumps to draw a vacuum down and make sure I'm holding vacuum, plus that will get any moisture out of the system in case I'm stuck for longer than expected.

How much oil and how much R134a should I suggest the tech add when I do bring it in? Should I drain the compressor first or just leave it alone? it's a Sanden SD5 and I have a variable orifice valve .



Also - is the 8 piston Sanden going to have noticeably better performance than the SD5H14? I'm not trying to find stuff to spend money on but if it's a no-brainer to upgrade, now's the time to do it.

[DMC5180]

134a 1.9 -2.0 lbs

Sanden ships SD-5 and 7 series compressors with 135CC of PAG Oil. If your system is clean you can use PAG. If you still have components contaminated with Mineral Oil you should use Ester Oil.

There is no 8 cylinder compressor that I?m aware of. I used the SD-7H15 with QD head and Adapters to go with DPI hoses.
More Cylinders provides for a smoother quieter operation. It really helped reduce the Idle pull down from the OE SD-5. My system has been working flawlessly since doing the conversion in 2016. I haven?t had to touch it since.


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[82DMC12]

134a 1.9 -2.0 lbs

Sanden ships SD-5 and 7 series compressors with 135CC of PAG Oil. If your system is clean you can use PAG. If you still have components contaminated with Mineral Oil you should use Ester Oil.

There is no 8 cylinder compressor that I?m aware of. I used the SD-7H15 with QD head and Adapters to go with DPI hoses.
More Cylinders provides for a smoother quieter operation. It really helped reduce the Idle pull down from the OE SD-5. My system has been working flawlessly since doing the conversion in 2016. I haven?t had to touch it since.


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OK I was probably thinking of the SD7 as you said. I'm not sure what you mean by QD head. Would the hoses and ends I have work on the SD-7H15 without needing extra parts or modifications? Do you just have to swap the back of the compressor over? Is there a gasket to worry about?

Sounds like both compressors will cool but you aren't seeing the RPM's get pulled down when it kicks in.

PXL_20221019_214523881.jpg

[82DMC12]

I found this service manual for the SD-5 compressor, which, on page 27, suggests that if you are replacing the accumulator only, to add 1.5 oz to the compressor to make up for what was lost/settled into the accumulator. That's easy enough.

I'm seeing PAG 46, 100, and 150 oil. I guess 150 is only used on a particular GM compressor from the 90's. Should I add 46 or 100 if I don't know what I've already got?

[DMC5180]

QD head comes with gasket. It is the closest to the the original SD5 head type. The ports are vertical ( inline with Filler plug) Bolt torque is 22 lbf. You can mount the compressor with the ports horizontal like OE configuration. I chose to install Vertical due to the Service port locations. IMG_0596.jpg


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[DMC5180]

I found this service manual for the SD-5 compressor, which, on page 27, suggests that if you are replacing the accumulator only, to add 1.5 oz to the compressor to make up for what was lost/settled into the accumulator. That's easy enough.

I'm seeing PAG 46, 100, and 150 oil. I guess 150 is only used on a particular GM compressor from the 90's. Should I add 46 or 100 if I don't know what I've already got?

I used PAG 100

I bought my compressor and replacement head from www.coldhose.com that was 6 years ago though.


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[82DMC12]

Thanks for the details.

Did you use a regular white GM orifice tube or did you use the black "variable orifice tube" that some were selling back in the day? I have a black one currently installed (I think).

Do you happen to know how long the bolts for the back plate are? That website sells them in 40, 45, and 55 mm lengths but they don't specify on the page which compressor/head uses which. I can call them tomorrow if you aren't sure.

[DMC5180]

Years ago I bought a Hervey hose kit that came with the variable Orifice tube. I used the VO tube but not the Hoses. Some years later DPI offered a Hose kit I preferred using a fitting system I had familiarity with it from my Work.

Unfortunately, I don?t recall the bolt length. I ended up getting the appropriate length bolt at my local Hardware store. You?ll have to measure the stack up dimensions to the face of the head surface and add 10-15mm for length.

Or just buy all three to CYA

My compressor build spec is CO4708C (chinese sanden) double V-belt ( black pulley/clutch assembly)

USA Sanden version is 4708C (I think)

[82DMC12]

Years ago I bought a Hervey hose kit that came with the variable Orifice tube. I used the VO tube but not the Hoses. Some years later DPI offered a Hose kit I preferred using a fitting system I had familiarity with it from my Work.

Unfortunately, I don?t recall the bolt length. I ended up getting the appropriate length bolt at my local Hardware store. You?ll have to measure the stack up dimensions to the face of the head surface and add 10-15mm for length.

Or just buy all three to CYA

My compressor build spec is CO4708C (chinese sanden) double V-belt ( black pulley/clutch assembly)

USA Sanden version is 4708C (I think)

Nice, thanks for the additional info. This one looks like the right thing, right, but it needs the QD head sold separately?

https://coldhose.com/collections/com...35532296126624

[DMC5180]

That looks like the correct configuration. You just have to swap to the QD head sold separately $25

You can also do a cross reference check to the CO4708C P/N I have.


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