Could a "tiring", 12 or 13 year-old compressor (Sieko-Seiki SS 1212 DS5, rotary vane type?) be causing 50-60psi Low Side pressure, warmer than last year vent temps at idle, and constant compressor engagement -- yet give vent temps in the lower 30°s at 50-60mph? Obviously the 50-60 psi LS pressure won't let the clutch cut-out at 23psi like the book says.

My "theory" is that at idle RPMs the compressor is weak, but at highway RPMs, with the extra airflow thru the condenser, it seems able to produce good cooling, even though my tell-tale light on the clutch says the pressure is still not getting down to the 23 psi cut-out value.

I've only had this car 2 1/2 years. The AC was inop, but fixed in '03 and OK for that summer. Last year it needed a condenser (OE), new High Side hose, Orifice Tube, and Accumulator to get cool again. OK for the rest of the season.

My local shop is of the "Country Store" variety. The owner/tech is very good with a wide variety of cars, but doesn't see many Volvos. He tried increasing, then reducing, the amount of r134a—with little effect on LS pressure and no effect on the clutch.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.