Hi,

my 1988 300e AC does not work since I bought it last year. I see a sticker on the car indicating die was added to find leak before I bought it. I have read few of the AC threads and suggestions are to go step by step to find the problem/s. The compressor does not engage and I like to first check its clutch. How can I apply 12V to the clutch short of applying it directly on the compressor terminal. I will do this when engine is not running so no further damage to the compressor may occur.

the other question I have is that the air blower motor is always on at a very low speed when the car is running even when the climate control is off (O button is pushed in). The blower otherwise works properly at all speeds.
where should I start to diagnose the problem?

Thanks

A quick way to test your compressor clutch is to put a jumper across the wires connected to the Freon Pressure Switch (the one without the pigtails) at the Drier. Start the car and turn on the A/C then look to see if the compressor is turning. If your freon is low or empty, the switch will remain open. You have to jumper this switch when charging the system from start-up, (replacing components, etc.).

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Thanks. Most likely this system is low or out of freon and that is why I thought I should do a static clutch test otherwise I may cause more damage to the compressor if it runs dry even for short time. Can I by pass AC relay and energize the clutch? If that is not possible then I would just apply 12V to the clutch terminal on the compressor. BTW, looking at the compressor and noticed a valve with a black cap on it. Is this the high side access connection?