AC Compressor Clutch. Volts but no Amps?

[James Forrest]

Hi all. I have a 97 Merc Grand Marquis with 12V from the harness to the compressor but no clutch engagement. When I check volts and amps through the harness to the compressor I get 12v and no amps – not even enough to light up my test light. Shorting the contacts at the connector on the low side of course makes no difference.

But with the plug on the low side switch removed I can run a lead direct to the 12v batt post and get solid clutch engagement and a 3 amp draw with my multimeter. Everything I know of points to something upstream from the low side switch that will not allow enough current to close the clutch. Any idea what to look for and where? Could it be a bad ground? If so where? I’ve checked contacts on the high *and* low side switches, relay box and ECM and they look clean.

I’m stumped. And hot.

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[James Forrest]

Anyone have or know where I can find a wiring diagram for the AC system?

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