Negative pressure

[Acrisoft]

Hi fellows

This is an automotive a/c system:
After charging, a student of mine is reporting negative pressure on low side port (about -27 hg) and about 100 psi high side port. I have literature about diagnostic by pressure but no one of them reports negative pressure cases. What can it be ?

Moises

[nike123]

Blocked expansion device, blocked filter-dryer, etc...

[jedax81]

negative indicates vacuum

[chillin out]

No gas in system, also the pressure switch has either failed or doesn't exist.

Chillin:):)

[jdunc2301]

a student of yours?!

[Kaiser]

I agree with nike123, blockage in L/L or TX.

[Gary]

I agree with chillin. An automotive system has a low pressure switch which disengages the magnetic clutch on the compressor if/when the pressure is low. It is not possible for the system to run in a vacuum if this circuit is functioning properly.