95 monte a/c recharge

My 95 3.1 monte just got a new compressor I can't get it to work unless I run dircect current to it .. It runs fine when hot wired .. any ideas.. and where is the low pressure switch ?

It's definately a leak or undercharge. The Low pressure switch is on the accumilator (Silver tank slightly larger than a coke can) Unplug it and jump out the contacts on the plug with a paperclip. If the compressor runs then it's a low charge. Get some 134A and a guage and recharge it or take it to someone who can find the leak.