I live in Wisconsin, so this is soon going to be an important issue for me. My blower fan will run awhile, then quit. Doesn't seem to matter which fan speed I use. Is it the brushes in the fan itself, the push button contacts, or some kind of relay? It got down to 28F last night. Hurry!

Try moving your key slightly anti-clockwise and see if the blower picks back up. As these switches age, they can get enough play in them to make the accesory contact intermittent.

Your other guesses are also valid, and it may also be the fan speed controller which is under the blower.

There is a connector behind and above the brake booster in the engine compartment with three pins, disconnect there and apply power to the fan /contoller directly. Two of the wires are for 12V +/-, third wire is the signal from the pushbutton controller that operates a variable voltage for speed.

See your maintenance books or CD for the test voltages and wire color.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Early W124s had the fan fuse in the fusebox and this tended to overheat. Check your fuse and make sure it's getting good contact.

Lots of cars were backfitted to the external inline fuse holder, so if it's not inside the fusebox, it should be to the inside of the master cylinder.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Before you dive into replacing the control, a royal PITA, don't just check the fuse, but replace it. Mine had a hairline crack that I did not notice until after I had the new fan controller replaced. Talk about annoying.

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63 190d (sold)
69 220D (sold)
69 280SL (sold)
76 BMW 2002 (sold)
86 190E-16v (Demised at Laguna Seca Turn 9)
87 300SDL (sold)
87 300SDL 135k
87 300TD 280k (sold)
95 E320W 211k
95 E320w 111k
05 C320 4matic
06 E320 CDI 90k (Totaled by a texting 19 year old girl in a nissan)
2013 GLK 250 Bluetek 4MATIC

Don't know if the CCU is similar to my '83 w123, but mine had the same symptoms -- blower would work right after starting for a while, then quit and would randomly come back on while driving. Only defrost seemed to work on mine, and the center vents never worked ever. Diagnostic was that if I hit on the front of the control unit, sometimes it would decide to come back on in response.

My problem was solved by resoldering the broken solder bridges to one of the wing boards inside the CCU unit. It has fised the cutout problem, the defrost-only, and the center vents never working (that was a suprise). This repair was so easy, I'm still kicking myself for putting up with it for a year.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

I'm the guy from wisconsin. The fuse for the blower motor isn't in the fuse box. Can anybody tell me where it is. For an 87 300TD? Thanks,
Bruce