124 A/C compressor won't kick in

[pdrayton]

The wife has a 92 300D 2.5D W124. The a/c worked fine last summmer, but now when she switches it on, nothing happens, ie the compressor clutch doesn't engage.

I know what you're thinking - check the regrigerant level. It is a conversion to R134a BTW. The only way I know how to check the refrigerant level is to plug in a gauge on the low side, which I did and got a reading of 55 (ie a bit high).

Since the compressor isn't on, is this a reliable reading? I remember recharging my truck and the pressure was high when the compressor wasn't on, but would drop way down when the compressor was on.

Sorry to babble here. Basically, is this a reliable way to check the refrigerant level, or should I get another can of r134 and plug it in and see what happens?

I read the merc manual 8-604 about checking 21 different electronic components in the ac system and almost screamed when the last test, #21 is for the compressor and it doesn't show a picture of the part N6 you're supposed to test. Or I'm confused.

Oh yes, I checked the fuses - all good.

Anyway, any assistance in getting the cold air blowing (we're in florida and already need the air) would earn me lots of brownie points with the boss......