Only happens on a cold start.. compressor won’t engage. If I shut the engine off then start it up again the ac works. Had it at the ac shop for recharge a month ago. Been working beautiful till this week. What should I look at first to diagnose? Rpm sensor?

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

You can get the error code from the 16 pin diagnostic connector in the engine room.

It will be the oldschool blink type code.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

How do I get a pin 16 since the +side decoder uses pin 16?

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1993 e300
1995 e320
1994 e320
2006 s500 4matic
2004 Jeep wj overland
2001 Ducati 748
2004 Honda shadow aero

the diagnostics port is 16 pin itself.

You need to make a the blinker with a moment switch to read the codes from pin 7 and 10 (did similar to diag my old E300D - and found that the clutch gap was large and was also oil soaked which was causing an RPM error).

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)