A/C Compressor does not kick on.....diode?

[whtailhunter319]

I tried to troubleshoot my ac in my 96ranger 4.0. System was empty, pulled a vacum 29hg held for 30 min, started adding refrigerant. Got enough in to kick on the LPCO. Compressor didnt kick on. Did power checks at compressor harness. Found 12vdc in both terminals. Found a diode in diagram. Isolated diode and tested bad. Ground tested good. Removed diode to give the clutch coil straight ground. Compessor started kicking off and on quickly. Im assuming the diode increases the field in the clutch coil??? Can anyone shed some light on this? Im going to get a new diode regardless and install it.

 

[MAKG]

The diode keeps voltage spikes from going back into the electrical system. All coils (clutches, injectors, fan motors, alternators, etc.) create voltage spikes when the current through them is changed.

Diodes usually fail to shorts, as you found.

Good work diagnosing. Now a standard diode from Radio Shack (oriented properly!) soldered in and heat shrinked will make for a bang-up repair.

And for something like 50 cents in supplies.