A/c clutch wont engage. the compressor and clutch are good i jumped the pins on the pressure switch,didnt work. i checked the relay.i jumped the pins where the relay goes and got it to engage.

Is the system full of refrigerant ? Low pressure cut out switch could keep the compressor from engaging > The PCM/ECM -engine computer controls the engagement of the compressor clutch. Rather then jumping the relay, test for power an control . If you pull the relay out of the fuse box an look on the bottom of the relay , you will see 4 sets on numbers 30 & 87 - 85 & 86 . you proved 30 has battery voltage by jumping it to 87 , now you need to check the control side of the relay . Pin 86 should have battery voltage while pin 85 supplies a ground through the PCM/ECM .

The low pressure switch is just a sense input to the PCM - powertrain control module > Grantit , it is needed for the PCM to know the pressure in the system . But the PCM must energize the compressor clutch relay for the compressor to engage . Finding the compressor clutch relay in the under hood fuse / relay box an testing there would be the best place to start . Pull the relay out of the fuse box , look on the bottom ! You should see four set's of number's ,30 & 87 plus 85 & 86 . 30 & 86 should have B+ voltage . Use a multi-meter to test . 85 goes to pin # 1 connector 3 at the PCM . The PCM supply's a ground here to energize the relay if condition's are right . You could jump pin's 30 & 87 an if the compressor clutch coil is good ,the compressor clutch will engage . Video's on youtube showing how to do these test .

Probably the high pressure switch on the accumulator - try disconnecting the connector and jumping the pins to see if the clutch will engage. If that is the problem, DO NOT leave it jumped - replace the switch.
If that is not the problem, you will have to check the clutch wiring, relay and fuse for continuity back to the HVAC controls. If that is OK, the problem will probably be in your HVAC control module.

Put a jump wire in the high pressure switch plug. If the compressor works. replace the high pressure switch. Let me know and we can go from there.

the ECM supplies the ground circuit for the a/c clutch. the high pressure switch also needs to be closed to engage the clutch. when the low pressure switch and the high pressure switch are closed that completes the power circuit to trigger the relay.then the power on the #30 terminal can connect to the #87 terminal to send power to the a/c clutch.

This could be a few things. The freon could be low, one of the switches (high or low pressure) could be bad, or you could have a bad compressor clutch. You can test the clutch by checking for battery voltage and ground at the two pin connector with the A/C on if you have both power and ground, then the clutch is bad. You really should start by hooking up pressure gauges to the A/C ports to check the pressures, and these vary depending on ambient temperature and whether the A/C compressor is engaged or not. I am willing to bet that the freon is low though and may be just as simple as recharging the system.
Hope this helps. Good luck!

you need to check to see if your refrigeration didnt leak out or the check the the clutch on the compressor

Did you try jumping where the Clutch relay plugs into the fuse/relay box ? Pin 87 & 30 are the compressor clutch coil power supply . If you look on the bottom of the relay you will see four set's of numbers 30 & 87 , 85 & 86 . If you take a piece of wire an jump 30 to 87 this will send B+ voltage to the clutch coil engaging the compressor . Is the PCM turning on the relay ?
The Trainer 40 When the compressor won compress

Check the connections on the plug going to the compressor clutch and on the pressure switch on the low side. Also check the gap on the clutch. It may be too wide after where to engage correctly. Good luck.

the control unit is no good.i had a similar situation with a 98 tracker,and installed a switch to give it a ground for the compressor relay that comes from the a/c computer module.
it works good and goes on and off with the a/c switch.