bad 190E ignition switch causes AC to fail?

Hello,
The AC stops blowing cold periodically but I can usually get it started by turning the ignition switch off completely and then back on. Just turning
the AC itself off and on or changing any of the modes and settings will not get it started. Is it possible that the cause is a faulty ignition switch and if so can anyone suggest how I would go about replacing the switch (and the tumbler--another problem)?
Many thanks,
Mike
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Yep, I had that problem... reason is worn weak spring on the ignition switch. If you just turn the key back a bit more without shutting the engine off, the A/C fan would kick on.
Ignition switch is done through the underdash... a real pain in the butt to do. As for the tumbler, if you have problem turning on the key... then change it asap!
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Thanks Tiger.
The fan doesn't stop unless I turn the AC off--it's just the cooling that stops. Still think it's the ignition switch? Do I need special tool to replace the tumbler?
Mike

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Just the cooling then I would double check your freon level... pressure probably too low.
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replying to Tiger, Christa4 wrote: I'm having this issue right now. I use to get the ac to function by turning the key back slightly but now when I turn the key back slightly it doesn't do anything. What is wrong?
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Yep, I had that problem... reason is worn weak spring on the ignition switch. If you just turn the key back a bit more without shutting the engine off, the A/C fan would kick on.
Ignition switch is done through the underdash... a real pain in the butt to do. As for the tumbler, if you have problem turning on the key... then change it asap!
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This doesn't sound like an ignition switch issue to me...
Seems more likely the AC is shutting off due to some pressure senser reading and that turning the car off and on again is resetting this?
Just a thought. Marty
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If the problem can only be corrected by turning off engine, then it is either worn/dirty/oily belt, or the tensioner is bad.
On W201 (and many other models around mid 80 to early 90), the accessory belt is a single serpentine type. MB designs the AC relay to compare the engine and compressor rpm. If it senses a difference of 30% (don't remember exactly, may be lower), the relay cuts off the compressor clutch, assuming the compressor seizes so it saves the belt to drive other vital accessories (alternator, water pump, etc.). The logic only re-engages the clutch after shutting off engine.
mharness wrote:

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May have discovered the problem with my AC--probably a bad AC control unit or temperature relay. I have a used control unit coming from Potomac for $75 and will find out soon enough if I'm right.
Thanks

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