After spending 7 weeks wrestling with a D2 ('04, 190K miles, total rebuild at 128K miles because of a slipped sleeve) that would start but then stall/die (after replacing a half-dozen parts, turned out to be a vacuum leak at the EVAP purge valve-to-intake manifold connector), now that it is running again, I have an AC clutch that doesn't appear to be working.

Here are the symptoms/observations:

• With the engine running at idle and AC off, the AC compressor clutch plate is static, i.e. not moving at all
• With engine running at idle and AC on, the AC compressor clutch plate is barely engaging, i.e. it is moving but just barely -- maybe one revolution every second or two -- and certainly not at the same speed/rate as the compressor pulley itself.
• With the engine off and jumpering the AC compressor at the relay socket, there no no distinct "click" indicating that the clutch coil has energized and pulled the clutch plate onto the pulley
• Same situation when 12v is applied directly to the compressor clutch coil connector, i.e., no distinct "click" that the clutch plate has engaged with the pulley.

Based on the above, I am suspecting a failing/failed clutch coil. (failing, because when the AC is on at the ACC head end, the clutch plate spins, but just barely and at a fraction of the rate of the pulley itself at idle; I have never seen this before, usually the clutch either engages or it doesn't)

I will put the ohmmeter on the clutch coil it today.

What should it ohm out at?

 

I'd nobody else responds, I'll try to stick a meter on mine when I get home.

 

Thanks. I'll keep an eye out for your reading.

Mine tested out at 4.1-4.2 ohms (the base continuity resistance of the probes when touched together on my multimeter is 0.2 ohms).

Also, checked the harness connector with the AC on, and there was 13.5V on the connector so I assume it is not an electrical issue from relay-to-coil.

Finally, after not "clicking" when either jumpered at the relay socket or with 12V applied directly to the compressor coil (using a 60W 12V power supply, so only 5 amps of current), and further after several cycles of not engaging with the AC on and the engine running, the clutch is now engaging sporadically (beyond the normal on-off cycle) and on such one engagement, the clutch kind of howled before fully engaging and settling down.

So still trying to figure out whether I have a weak coil (the ohm reading of a known good coil would help) or maybe a worn compressor clutch plate.

If it's not a weak/failing coil but rather a worn clutch (based on comparing to the ohm reading of a known good coil), could I take the clutch off and remove one of the spacers to reduce the clutch-to-pulley spacing to effectively get more life out of it?

 

I have seen a few worn clutches, that would be my guess assuming the bolt is still in place holding the nose on.

 

Usually on the Denso AC Compressor the actual clutch surface over time cracks and just eventually can no longer engage. I haven't seen the electrical side actually fail in my personal experience yet. All the units I've seen had pieces missing from the clutch plate itself or it was very rusty and it slipped and caused the rubber ring to melt and render the AC Clutch useless.

 

Sounds like that could be the issue.

I should be able to remove the clutch plate and inspect it without taking off the serpentine below.

Not sure I can get an impact wrench in there?

How would you approach removing the clutch plate to inspect it?

 

Hold the clutch plate with a strap wrench and loosen the 10mm bolt. Be careful not to loose the spacer which will be up inside the shaft of the clutch plate!

 

Since coils inherently have inductance rather than resistance your ohm meter won't tell you much other than you don't have an open or a short.

 

Open or short is all you need to know, 80% chance it is a slipping clutch and not a coil issue.

 

Sorry fro the delay! I was finally able to ohm mine out and came up with 4.2 ohms, same as you.