O.K. MB gurus I need your help! I searched the forum and couldn't find a problem quite like mine.The car in question is a 1990 420SEL which I have owned since September. It started out intermittent. Sometimes when I got in the car the air conditioner would work, sometimes it would not. It was like that for a little better than a week, and then it just completely died. No blower in neither air, heat, or defrost modes. However, sometimes when you put your hand up to the vents it might feel cold, or hot or nothing at all. What mode the climate control is in has no bearing on the temp that you feel inside the vents. The other day it was nearly 90 degrees outside and there was Extremely hot air inside the vents. This was with the temp control turned to Max. cool, and the "off" button engaged. Today is a nearly identical day temperature wise, and with the controls in the same configuration, I can feel that the air inside the vent is nice and cool. Again, the blower does not work in any case. The only trouble shooting I have done is to replace the #5 fuse. It looked good but I know that appearances can be deceiving. I am not a DIY guy when it comes to cars, so it will be going to a garage for repair, but I wanted to be able to talk with the mechanic with some degree of intelligence. Also, I need to be prepared for just what I am in for. Again thank you all for your help.

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87 300SDL 278,000mi - RIP
82 300SD 260,000mi - RIP
84 300D 178,000mi - SOLD
90 420SEL 178,000 - Daily Driver

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you could have burned out the climate control head. I'm pretty sure, the aux pump failure applies to your car. unplug the aux pump on the driver's fender, and check to see if it's seized. when it does, the extra amp draw can burn out the climate control. or it could be simple solder rings failure. pulling out the control is a pain, but once you get it out, pop the cover off, and see if anything is burned, or if there are any white rings on the joints.

Strip fuse for blower is out, or the motor is bad or the regulator. I am betting on the fuse tho.

I had that intermittent problem for a few weeks on my 400E. It eventually did not blow air at all. It turned out to be the blower regulator. The good news is, if yours turns out to be the regulator, it looks like it would be easier to get to than on my 400E.

http://www.peachparts.com/shopforum/showthread.php?t=71166&highlight=420sel+blower+regulator


http://catalog.peachparts.com/ShopByVehicle.epc?q=1990-Mercedes--Benz-4--0sel-Climate--Control&yearid=1990%40%401990&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6266%3AMBC|1533%3AED|10000055%40%40420SEL&catid=242213%40%40Climate+Control&subcatid=242297@@Blower+Regulator&mode=PA

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

Could be regulator, but that strip fuse is cheaper to check first.

Thanks to all who responded. Macdrone hit the nail on the head. It was the fuse, the hidden one on the fender.

__________________
87 300SDL 278,000mi - RIP
82 300SD 260,000mi - RIP
84 300D 178,000mi - SOLD
90 420SEL 178,000 - Daily Driver

This message was generated using 100% recycled electrons.