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Old 10-04-2002, 06:45 PM
Posts: n/a
blower fan / climate control 260E

My blower stopped working. Have checked fuses. Other posts have suggested checking the control voltages coming off the CCU pushbuttons by disconnecting the connector just under the windshield, behind the power steering, almost at the firewall. Per post black wire is ground, red is battery, and yellow is control. I checked the voltages at the wire side, black to yellow or black to red wires gives no voltage. I also opened up the CCU and checked continuity between the small circuit board for the blower pushbuttons and the main CCU circuit board. What next?

Robby Roll
San Francisco
'88 260E

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Old 10-04-2002, 07:14 PM
Posts: n/a

Well, if you have a real steady hand, you can resolder the board and the connections leading to the deal and fan buttons. Just heat up the solder so it melts and then pull away. Use a 25 watt soldering iron and be careful when heating the solders.

Otherwise, buy one from About 60 bucks.

Good luck,

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Old 10-06-2002, 02:21 AM
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I am a little unclear, does the fact that I had no voltage at the wire harness I checked indicate that the CCU is bad (or the CCU sub board you noted in the reply)?

Thanks for the clarification.
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Old 10-06-2002, 12:15 PM
Posts: n/a
Hi Robby,

Good question:-)

Do you have the service manual for the car? If so, you can print the wiring diagram and follow the power path from the fuse box into the car until you find a fault.

Did you check the relay(s) as well?

There are a variety of fuse locations on my 300E. A small fuse box a little forward of the main fuse box and towards the engine.

Also, replace all of your fuses with new ones. Don't assume by looking at them that they are okay. This solves a variety of ills. Old fuses go bad and it's hard to spot the problem. They look good but are in fact blown. While you are at it, clean the contacts as well.

Check on the retro fit fuse between the aux water pump and the ACC unit. I recall it being a 1 amp fuse.

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Old 10-06-2002, 02:33 PM
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Join Date: May 1999
Location: Sacramento, CA
Posts: 1,565
I've tried checking the wiring harness by the brake booster on two 300E's, and both times I was unable to obtain any voltage signal, even though the CCU was giving a good signal. In both cases, it turned out to be a blower fan related part.

What I have heard is that when the CCU goes, it goes completely. If your A/C compressor is engaging and/or the vacuum elements are actuating the air vent flaps, then the CCU is probably okay.

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Old 10-06-2002, 03:07 PM
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I've tested the blower pins coming out of the firewall, behind the brake booster, after removing the wire harness. From Left to Right, Pin 1 is ground, pin 2 is Battery, and pin 3 is the control voltage. This did vary depending upon which fan button I pressed. I removed the flat fuse, cleaned the contacts, and checked it for continuity. Also removed fuse 7 and checked and cleaned.

From other posts on this subject this now leads me to the blower regulator or blower. From these posts I see that this is somewhat complicated to get to and includes removing the wiper unit then "digging down" to eventually get to the blower and regulator. I think I will leave this to a qualified MB repair shop to perform.

Thanks everyone for the assistance and I will post when it is repaired with the exact problem repaired.
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Old 09-07-2009, 09:53 AM
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Join Date: Sep 2006
Posts: 2
removing the wiper is not complicated. the whole assy comes out in one piece. My problem, I got to the motor but it wasn't the problem. with a voltmeter across the disconnected wires, my voltage did not change with the control buttons. always 11v. ??

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