The compressor wil blow cold air if I run a hot wire directly to it, but will not work with the switch.

 

A bad switch, maybe? Have you tried jumping the low pressure switch?

 

Is that a diode, capacitor, or a resistor. Mine does not have one. In fact, my connector looks entireley different!

A didoe is like and electrical check valve. Lets current flow one direction only.

Barrel shaped diodes are normally clack with a silover stripe around one end. Resistors can come in any config. What are all the numbers on it and any symbols like the "Omega" symbol?

More info on your truck may help........did you check electrical diagrams?

If you jump the compressor and it runs, it indicates tha something inthe control circuit is not making. Possibly high or low refrigerant, etc.

 

Diode snubbers
Main article: Flyback diode
When the current flowing is DC, a simple rectifier diode is often employed as another form of snubber. The snubber diode is wired in parallel with an inductive load (such as a relay coil or electric motor). The diode is installed so that it does not conduct under normal conditions. When current to the inductive load is rapidly interrupted, a large voltage spike would be produced in the reverse direction (as the inductor attempts to keep current flowing in the circuit). This spike is known as an "inductive kick". Placing the snubber diode in inverse parallel with the inductive load allows the current from the inductor to flow through the diode rather than through the switching element, dissipating the energy stored in the inductive load over the series resistance of the inductor and the (usually much smaller) resistance of the diode (over-voltage protection). One disadvantage of using a simple rectifier diode as a snubber is that the diode allows current to continue flowing, which may cause the relay to remain actuated for slightly longer; some circuit designs must account for this delay in the dropping-out of the relay. This delay often leads to greatly decreased life of the relay contacts due to arcing.

 

Don't recall seeing a diode on harness to compressor on my truck. Going to look now.

 

Mine does not have one. Nor does any of the other 6 vehicles I have that have AC. 12v and the minimal load of a clutch would not create an issue where a snubber would be required. DOn;t know why it is on there, as it is not necessary.

If it fails, it would fail open, and not interrupt the circuit. The problem ou are experiencing is due to something in the control circuit not making. That is why jumping it will bring it on.

 

I don't have one on my 2000 1500 either. They are pretty common on GM vehicles.

 

sorry I haven't gotton back sooner. The freon is where it should be. I've tried jumping the high and low pressure switch. I also jumped all the wires on the switch on the dash. I've switched the relay with a known good one from the horn. I'm at a loss. I do not get fire to that harness plug. By the way the truck is a 95 3.9.

 

Check the horn fuse......

 

The horn fuse is good.