A/C no power to the compressor

[khalil235]

I have a 95 Pontiac GA it's blowing hot air.
I check the compressor PSI is O.K. and the clutch can be turn by hand.
When I turn on the dash switch the clutch does not engauge.
I got no power at the compressor (using a test light w/the connector unplug) I have a three prung low pressure switch (located on the high pressure hose) not sure how to test it. Also is there any other relays I can check (checked A/C - Heater fuse O.K.) When I take out the A/C fuse and put it back in, I hear a clicking sound near the master cylinder.

Any advice where to check next........

[ctesla]

khalil,
Welcome to AF.
now you say on the hi-side AC line the switch/sensor is three prong?
somewhere, located on the hi-side AC line heading back to the firewall and evaporator is this switch the one you're talking about?
the more common cycling switch from GM is two wire.
some systems have more than one.
if you do have a two-wire switch in the line, unplug it, and with a solid wire, jumper the plug quickly.
if the clutch cycles on, you may just have a bad switch.
most all of these are in the $10-20. range.
when you say: check compressor psi, do you have a manifold set?
can you check hi and lo side simultaneously?
if you have a clogged orrifice tube (expansion valve), the system isn't flowing properly, and the compressor clutch would not kick on.
if you do not have a manifold set, pay the $40-80. for a technician look at it for an hour, as then with a proper diagnosis, you can (while it is in the shop) have it done, and they might cut a deal (being they've already troubleshot), or come home, knowing what precisely you need to do to get it operational.
with the cost of 134a(unless you have your own evac machine to re-use your old 'freon'), sometimes the cost of having the shop do it (since they will evacuate, purge, and recharge the system) is almost the same as out of pocket.
hope this helps