Another technician at our company installed a new compressor in a Lennox Heat Pump the other day, wired it up, weighed in the charge and was testing the unit. He said it ran OK for a short time, then the low side pressure started dropping until it went into a vacuum. He said the high side pressure stayed around 110 psi or so while he had it on.

As it turns out, I'm supposed to go out there in the morning to figure out what went wrong.

Any ideas?