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I hooked up the a/c on my 79 this weekend and all was well. Holds vacuum with no leaks, and compressor engages with the switch. New drier, filled compressor with ester oil to lubricate it. Compressor is a bit noisy, sounds like dry bearings. Anyway, after a fresh charge of freon, it won't blow cold. I think it may be the expansion valve. Any suggestions?

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Yellow 74 LUV. Factory a/c
Blue 79 LUV. Factory a/c almost there
Silver 78 LUV. California emissions donor car now gone
White 79 LUV. Factory a/c

My trucks run perfect 60% of the time all the time
Tucson, AZ

With the noise indicated i would be checking that the clutch is truly engaged and not just slipping. Make sure the entire center of the pully is in fact turning the compressor internals. Just my thoughts.

As egg suggested identify the rattle first. Once that's addressed, see if things improve. If not, a clogged expansion valve could be an issue. If you have access to gauges it's pretty easy to determine if the compressor is building pressure and if there's a restriction in the system.

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Tom
'81 Luv diesel 4X4 - daily driver

What Freon are you using?

Need to know what the high side and low side pressures are.

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Certified pilots, looking down on people since 1903.

I'm using 134a for now, until I know the system is fully functional. Then I'll put r12 in it. I placed an order for a new compressor today, but the guages indicate that it could be the expansion valve. Compressor seems to be working correctly, as there is a lot of head pressure in the system. I'll see if I can't get some guage figures up soon. Does anyone know where the expansion valve is located and if there is a way to free it up for now without replacing?

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Yellow 74 LUV. Factory a/c
Blue 79 LUV. Factory a/c almost there
Silver 78 LUV. California emissions donor car now gone
White 79 LUV. Factory a/c

My trucks run perfect 60% of the time all the time
Tucson, AZ

Assuming that you do have an expansion valve. Some do and many don't, just use a metered orfice/tube instead.
If it has one it would be located at the evaporator, which means either at the firewall or inside the heater/ac unit itself.
Normal pressures at about 70 deg ambient would be 180-240 psi on the high side outlet and 26-35 psi on the low side connection. These are of course approximate with the ratio being the key.

Where did you order the compressor from? Those are hard to find. I had to have mine rebuilt and it's broken again now.

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OK, I'm over it. Where's the beer?

I found a few on eBay right now. They're remans though, but all I did was search sanden sd508 and a bunch came up

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Yellow 74 LUV. Factory a/c
Blue 79 LUV. Factory a/c almost there
Silver 78 LUV. California emissions donor car now gone
White 79 LUV. Factory a/c

My trucks run perfect 60% of the time all the time
Tucson, AZ