Anyone here had any experience with a defective AC expansion valve in a W123? What were the symptoms?
Pressure readings? Is it possible for an expansion valve to stick wide-open, reducing the pressure difference between the high and low side enough to prevent cooling? Thanks in advance.

Happy Motoring, Mark

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DrDKW

I think I had that happen once. I was traveling and had my system blow up, ended up taking to some indy shop for repair. After he replaced most of the system, it wasn't cooling at all. When he put the gauges on it, there was little difference between the high and low side pressures. I suggested he replace the valve again, which fixed the problem (until it blew up again because he didn't do a good job flushing the system).

My '82 240D had a rebuilt compressor, new rec-drier and R12 last summer, but unfortunately, the expansion valve wasn't replaced at the time.
Since then it often starts out cooling fine, but anywhere from 5 minutes to a half-hour later, cooling starts gradually dropping off. Then if I park the car awhile, it may start working OK again - maybe even for the rest of the day. When I pressure-checked it during a non-cooling phase, it had nearly equall pressure in the high and low side. Some are saying that I need another compressor. But I think a defective compressor wouldn't gradually weaken, then fix itself and work fine until next day. So I'd like to try and rule out the expansion valve first before going in to replace anything else, and risk losing any of my precious R12.

Happy Motoring, Mark

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DrDKW

I would start with the expansion valve.