Getting down to the nitty gritty with figuring out why my A/C compressor clutch won’t energize. To be more specific, I’m trying to figure out why my Fan Control Module isn’t sending 12V to the compressor clutch.
I finally got ahold of a schematic thanks to 97forumaws6’s access to Mitchel1, and wrung everything out. It all checks out OK.
I got ahold of this diagnosis procedure, which mirrors my schematic perfectly:
How to Diagnose A/C System On 2000 VW Jetta GLS
- Check for an 11-volt reference voltage at pin T14/3. The reference voltage originates in the J293 fan control module and can be grounded by |the power control module (PCM) under certain circumstances (typically wide open throttle or vehicle overheat conditions) to turn the A/C compressor off.
If zero volts are present, the PCM is commanding “compressor off” or the wiring harness is shorted to ground. Raise vehicle idle speed above 2500 rpm and observe compressor operation and voltage at pin T14/3. If the voltage at pin T14/3 returns to 11 volts with the idle speed above 2500 rpm and compressor operation resumes, then a throttle basic setting procedure is needed and must be performed with a factory-compatible, by-directional scan tool. Note: A loss of throttle basic settings will keep the compressor from activating.
Bingo. No voltage. Pin T14/3 was continuous with ground. So I yanked the rain tray and pulled the plugs off of the big box in the middle (ECM?) and no more continuity with ground.
So it seems that my ECM is grounding the signal, keeping the clutch from energizing. According to the procedure I found, this means that I lost my basic throttle settings a year ago. Seems kind of odd. I don’t really know what that means, but I would think it would show up in driveability issues.
So for now, for no reason other than I’m out of options, I’m trying the magical useless unplug the battery overnight procedure.
Anyone have the ability to set my basic throttle settings, whatever that means? I’ll bring beer.