I posted a question not too long ago about why my fan was not kicking on for my A/C all the time. This was burried in the 5 or 6 other questions I posted as I just picked up the car and I am now like a child with ADD trying to fix things and learn as much as I can in about an hour.

Any way, someone posted an obscure reference to "wiggle the key". I saw it, but did not think much about it until yesterday. I was warm yesterday, so I did miss the A/C a bit. When it did not kick on I figured I would try the wiggle the key thing, no way it could work, right? Wrong; it worked.

Wow, y'all sure are some geniuses out here. Now the question is, why did it work? It must be electrical and have to do with the ignition system, but I am flying blind here as I cannot find a shop manual for the 86 300 SDL.


Thanks,

TOm

If you own a couple of 126's for a while you learn all sorts of stuff that's not in the manual.....

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There must be very slight wear in the ignition module over time where contact only just ceases to be made for the circuit that goes to the blower. Adjust the key a smidgen and contact is made again and voila!

- Peter.

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The tumbler you insert your key into is not the ignition switch. The ignition switch is on the back of the entire column lock, ignition switch and key casting. There is a flat rod that connects the tumbler and the switch.

The possibilities are play in the flat connector, a loose switch (held onto the casting by 3 screws), or a bad switch.

Pulling the instrument panel will help you get your hands on the switch portion, disassembly is required to check the flat rod.

Depending upon the value of the car, just turning the switch ccw slightly after starting can be considered a permanent repair....

jim

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The reason it works is because your problem is the electrical portion of the ignition switch. It is sometimes not making contact and sending power to your climate control system, wiggling it makes contact (until it wears out completely). I had the same issue on my 300D, replacing the switch fixed it completely. This is the part:

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ423Z0O47X4&year=1986&make=MB&model=300-SDL-001&category=All&part=Ignition+Switch

You guys are great! The $%$(*% dealer wanted to charge me $500 to replace the whole blower motor because they found the could restart the A/C by tapping it. I bet if I replace this it fixes the on/off problem.


One other question, I am not sure it matters, but when the A/C kicks on it blows out the vents on top of the dash for a while. This only happens when the car is real warm. Is this normal? The dealer also indicated this was due to the fan being worn.

They do have some oddball vent rules.

Watch that dealer! I did take mine in for a IP timing check and brake flush. I do buy parts there, but I wouldnt count on them for most mechanical tasks. Find an indie who can work on the car.

Is there a diagram or write up on how to do this?


I hate not havng the stupid shop manual.

OK, I have the Ignition module. Is there a write up somewhere on how to put this thing in?

I am not sure how to pull the instrument cluster, so I am flying a bit blind here.

Thanks as always, all help is appreciated.

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Instrument cluster, Odometer, Speedometer, Tachometer links

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