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#1
07-02-2006, 10:54 PM
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Cruise control quits if disengaged by brake pedal (83 240D)
The cruise control wasn't working on the beater (1983 240D). So I did the check on the cc switch - all good, so I then did the ol' standard resoldering the cruise control amp connections and whoopee! it worked!
But my excitement was short lived. It stopped working until I turned the car off and started up again. I later discovered that it is only when I pushed the brake to disengage the CC that it wouldn't reengage. I checked the connections to the brake pedal switch. The switch is fine - closes when the brake is actuated (as the Krauts put it in the manual). However, the wiring in the manuals doesn't match the wiring in my car, so I don't know what the deal is. But none of the wiring seems to match, yet it works fine, so I think I must have some different wiring becuase it was a later model and they changed the wiring but didn't change the diagrams. Anyway, mine looks like this - 4 wires (2 green, 2 black I think) come down to the brake pedal. One goes to one pin of the connector, the other 3 go to another connector and are basically all connected together and back to the other pin of the connector that goes on the brake switch. Basically, I don't think the wiring at the brake pedal is right. Any ideas about how it should be? Anyone feel like getting under the steering wheel and seeing what there brake pedal wiring looks like? Or maybe you've had the same problem and fixed? Calling all gurus....  Before you ask, yes, the brake lights work and the ground is good! I checked that one. Thanks! 
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#2
07-03-2006, 02:27 PM
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Pressing the brake pedal, or disengaging the clutch will disengage the cruise control. Pulling the cruise lever to wards the driver ("resume") will re-engage the cruise control and resume the previously set speed.
Is your cruise control resuming when you pull the lever after hitting the brake? if so than this is normal. Dave
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1970 220D, owned 1980-1990 1980 240D, owned 1990-1992 1982 300TD, owned 1992-1993 1986 300SDL, owned 1993-2004 1999 E300, owned 1999-2003 1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD 1988 560SL, 100,000mi, owned since 1995 1965 Mustang Fastback Mileage Unknown(My sons) 1983 240D, 176,000mi (My daughers) owned since 2004 2007 Honda Accord EX-L I4 auto, the new daily driver 1985 300D 264,000mi Son's new daily driver.(sold) 2008 Hyundai Tiberon. Daughters new car
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#3
07-03-2006, 03:32 PM
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No resuming!
DAve, that's just the thing. After I press and release the brake,the CC releases, but then it won't switch on again. It won't set, accelerate, decelerate, resume. Nothing. I have to swtich the ignition off and then on again. Then the CC Works until I use the brake. If I use the "off" on the CC lever, I can resume again without restarting the car.
That's why I think it must be some bad wiring in the brake pedal - the system only becomes non functional after the brake pedal is pressed. Paul
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#4
07-03-2006, 04:43 PM
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An interesting problem
Well, interesting to me, frustrating to you. I don't think it is the switch at the brake pedal but rather something in the cruise amp (the board that you resoldered) that is causing this problem. My suggestion is to again remove the board and inspect it carefully for any solder bridges you might have accidentally made while resoldering the board or any points missed. I know from my own experience resoldering this board (twice) that it is easy to miss one and that's all you have to miss is one.
My schematic of the wiring that is common to the brake lights and the cruise control shows pretty much what you have described -- one wire to one pin of the switch on the brake pedal (brings +12 Volts from the fuse panel) and three wires tied together on the other pin. Of these three wires, one goes to the cruise control amplifier board, one to the cruise control actuator (the mechanical thing that operates the throttle), and the third to the brake lights. There's nothing in the actuator that would "latch" off so it has to be in the amplifier. Jeremy
__________________
 "Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970
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#5
07-03-2006, 05:17 PM
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Thanks Jeremy - you might well be right on that.
Is it possible for you to send or post the schematic you have for the brake pedal switch? the one I have is wrong I am sure - it shows 2 wires connecting to each of the pins on the brake pedal switch, which is not what it is doing. I am still a little suspicious of the wiring there. Logic and probability indicate the amp, but emotional resisitance to the work and bent neck involved have a powerful influence on the situation....
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#6
07-04-2006, 12:36 AM
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Schematic
Quote:
http://mb.braingears.com/ You must access this site with Internet Explorer, it does not work with Firefox. The schematic is page 111 of the factory electrical manual; braingears calls it "83_300.pdf." You can download the entire pdf file, in which the schematic is page 22 of 30 pages. Jeremy
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"Buster" in the '95 Our all-Diesel family 1996 E300D (W210) . .338,000 miles Wife's car 2005 E320 CDI . . 113,000 miles My car Santa Rosa population 176,762 (2022) Total. . . . . . . . . . . . 627,762 "Oh lord won't you buy me a Mercedes Benz." -- Janis Joplin, October 1, 1970
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#7
05-24-2013, 11:52 AM
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From the wiring diagram, check to see if you get +12Vdc when the brake pedal is pressed at:
Pin 8 of the Amplifier Pin 6 of the Servo (The copy of the diagram, on page #1 of this thread, is a little fuzzy on my computer.)
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Sam 84 300SD 350K+ miles ( Blue Belle )
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