my 2000 3.9 dakota, ac clutch wont engage? freon level is right between red and green, 55psi on ac pro gauge. i have 13-14 volts at compressor conection and 0 continuity at low pressure switch with voltage going to it. the switch on passenger side on top of big aluminum can looking thing i think hi side,continnuity was 1. and when i added thelittle shot of freon comp was not running. any help thanx in advance, i did swap relays allso

 

If you have 13 volts or so at the compressor clutch, it should engage.

You should have continuity at the low pressure switch though. The PCM receives a signal from the low pressure switch and engages a relay (in the PDC under the hood)to turn the compressor on/off.

As to the 55 psi, if the compressor isn't running it isn't much of a help. Pressure are measured when the compressor is engaged and you really need both high and low to determine how well it is functioning.

Jump the low pressure switch and see if the clutch engages and read the pressures while it is running.

 

thanx dan, i put paper clip in wire going to low pressure switch, still no clutch action. when i put olhm meter in low switch it said 000 wich means i have continuity,is that good.

 

0 ohms resistance means the switch is closed, has continuity. In your first post when you said "0 continuity" that would mean it was open.

You are measuring with the connector off, right? You don't want the rest of the circuit to screw up your readings. The switch isn't keeping the clutch from engaging.

Have you checked continuity on the compressor clutch?

Try using a test light at the clutch, not a meter. It puts more of a load on the feed/ground.

 

00dan thanx,i used ohlm meter at compressor and read 000 same as low psi switch. have voltage at comp with test light and meter. all controls in cab also seem to be ok

 

If you have voltage at the compressor clutch, 12 volts, it should engage. Using a test light it illuminates? You are using the connector for the ground too?

You say you have 0 ohms resistance when you test the clutch coil - something is wrong then. You are unplugged when you are checking this right?

The clutch coil should not be reading 0 ohms. It's a coil of wire and has resistance and should measure between 3 and 6 ohms resistance. That would give you a current of about 2-4 amps at 12 volts.

You can always try just running 12 volts to the clutch direct from the battery to see if it engages.