could be the low pressure switch or the wiring to it.. seems like when you messed with it, it started working again, maybe a short? You could try swapping the ac relay with another relay of the same part number in the relay box. How many miles are on the car / compressor? Pressures dont seem to be off too much.. r134 should be about 2.2 times ambient temparature. r12 should be about 2.0 times ambient tempurature.