Equal (70 lb) high and low side pressures part way into charging rebuilt ac:

I have resurrected my 1981 300D's ac with rebuilt compressor (Napa - done by Four Seasons), parallel flow condenser with custom made hoses, new receiver drier, new o-rings everywhere. I also flushed individual lines and the evaporator prior to all the new parts. Goal is R134a - way good enough for Seattle.

I used the BG Frigi-Quiet oil that Diesel Giant likes so much: 4 oz in receiver drier, 4 oz in compressor (with hand rotation). Also rotated about 12 times with compressor lines attached.

So, I take it the shop for leak test and recharge. Holds vacuum very well. After evacuation, shop guy added one can of R134a and we had enough pressure to engage the clutch. But the high and low side pressures stayed equal at about 70 lbs. Hmmmm ... guy suspects clogged expansion valve or compressor not pumping.

I'm poised to replace the expansion valve as the path of least resistance. I did not replace this originally - my replacement from a certain firm in Arizona was of such poor quality that I decided to try to clean the old one (probably the MB original) and hope for the best. Old one had some small grunge particles in it probably from previous seized compressor.

Can a clogged expansion valve cause equal high and low side pressures like this? Did we put enough refrigerant in to adequately test the pressures? My limited knowledge says that this sounds more like a compressor problem. ??. Other causes?

ACC controller works fine as far as we exercised it. Pushbuttons "A", "B", and "C" all engage the clutch, "D" and "E" disengage clutch.

Thanks
(going to be low 90s here in Seattle on Saturday!)

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Erlend
1981 300D 202K daily driver

No. It would cause the high side pressure to be high and the suction side to be low.

What are the static pressures?

Static Pressures are both 65-70.

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Erlend
1981 300D 202K daily driver

Then you compressor isn't compressing.

I had that problem, too. I installed it anyway and it leaks slightly. Again, I relearn the "you get what you pay for" lesson.

Got my system working. Replaced Compressor, Drier, and Expansion Valve. Got parts from Polar Bear. $300 for all.

This is a plug for Polar Bear, Inc out of Ft Lauderdale.They rebuild A/C compressors. 800-365-3516. Speak with Gretchin. She's very helpful. Prices and service are great.

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92 300D 2.5L OM602 OBK #59