325i AC question about low side pressure
 

I have taken my AC down and had the compressor rebuilt and resealed and put a new dryer on. When I put the vacuum pump on it there was no problem holding 30 lbs. of vacuum, but when I started charging the system, after adding 4 oz. oil, my low side would not come down below 65-70 lbs., even though the high side went up to 250-275 like it should. The car doesn't cool very well at all and I suspect that I have a defective expansion valve.

Can anyone verify this to be the case, or let me know where else to look for the problem.

Thanks in advance.

Jake,

Expansion valve is a high probability but stop by a local dealer and try asking a tech about it. (I don't have specs handy - sorry) :dunno

How much refrigerant did you put in it? The pressure gradient relies on ambient air temp also. Pressures will vary, somthing to do with boyls law or something. The low side seems high but this could be due to over charge. Did the a/c get cold while charging? A lot of times if you know you had a good 30 inch Hg vacum, charge using the low side gauge. Depending on your gauges the R-134 ring should be charged up to 30 psi or degrees F, ignoring the high side due to its relience on temp. If it is not overcharged I would also be inclined to think it was the expansion valve.