Does anyone know how to fix a cruise control amp on a W126? it seems to me i read somewhere that there is something you can solder back together.

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• 1993 Mercedes-Benz 400E *146,000 Miles*
• 1985 Mercedes-Benz 300SD Turbo Diesel Biodiesel *SOLD @ 346,000 Miles*
• 1984 Mercedes-Benz 300D Turbo Diesel Biodiesel *SOLD @ 284,000 Miles*

Sometimes cold solder joints are the problem.. you just reflow all the solder joints and add some to any suspect areas.

FWIW I tried this on my car. It worked great for 3 weeks... then it went back to being broken.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

I re-soldered everything and the cruise worked once, then stopped.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

Where is the cruise amp located? My 300D will accelerate using the CC stalk, but it won't hold the speed.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

remove the underdash panel and you should see a big silver box down by the brake pedal. Thats the amp. Its a PITA to remove due to the space.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

As has been explained on this issue in the past here on the forum, the resoldering seems to "re-fire" several capacitors that go bad in these amps. Seems like there are 6 or 8. The soldering causes these caps to work again for awhile, but they will go bad again.
Seems like there is something posted about replacing the caps, including part #'s from Radio Shack or a similar supplier....

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

well it is worth a shot i have a long drive tomorrow so it would be at least worth having it for the weekend

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• 1993 Mercedes-Benz 400E *146,000 Miles*
• 1985 Mercedes-Benz 300SD Turbo Diesel Biodiesel *SOLD @ 346,000 Miles*
• 1984 Mercedes-Benz 300D Turbo Diesel Biodiesel *SOLD @ 284,000 Miles*

It's a lot easier to do if you get the lacquer off. Soak the unit in acetone.

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My Primary Driver - '85 300CD - 4-speed conversion, 2.47 rear, lowered, euro headlights, rebuilding (not restoring so much)

Wife's - '08 Saab Sportcombi Aero

Riding a '03 Yamaha Warrior

Yes, it is! Use a wobble 10mm socket. Take the seat all the way back.

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83 SD

84 CD

Ya that bolt is a PITA to get at! Thankfully I have short arms.

FYI on the W126 at least the buzzer unit is on the same bracket as the cruise amp. The driver's side door switch is connected to the buzzer unit. If you unplug it the dome light and door lights won't work.

a quicker "cheat is to carefully bend the aluminum tabs straight and slip board out since you have to remove it anyway. Get yourself some acetone, and a brass brush. I found mine in Walmart of all places. Dip brush in acetone and gently brush the connection side of the board. You want to see silver color on the solder connections. Once you have the lacquer cleaned off, you can take a pencil type soldering iron approx 25-35 watts and resolder the connections. With a magnifier you will see the "ring" cracks. From years of hot/cold cycles the solder joints expand and contract and crack. Be very careful resoldering around the IC's (black rectangular guys with multiple legs). Be careful of solder bridges, which is where the solder accidentaly flows accross two connections. While your out purchasing things, hit up your local Radio Shack, or Electronics supply house and get a roll of "solder wick" Great stuff! If you do happen to bridge any connections, you will be able to "wick up" the excess solder. When your done, just look the board over carefully and then slide unit back up into the aluminum box. With a pair of needle nose pliers or carefully with a screwdriver you can rebend your tabs back over and it will keep module in the housing!

Happy Turkey day!!!
Rick

Radio shack also has a nice desoldering iron. It's an iron with a hollow tip and a sucker bulb: you can suck the solder right out of the joints.

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Jimmy L is quite correct about this, I've resoldered the amp on my W126 on three separate occasions. First time worked great for about a year, 2nd time for about 6 months, 3rd time was a charm....about 2 weeks! Perhaps time for a professional rebuilt unit if I really want a working cruise control.

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BENZSTER

W123, '81 240D, Pastel Grey/Blue Tex
W126, '88 300 SEL, Artic White/Grey Leather

Something you need to know before resoldering . . . Last time I read the advertisements for the people who rebuild and sell cruise amps and similar things, they won't accept your amp as a "core" if it has been resoldered at home. Without your virgin core they will want more money for their rebuilt unit.

For example, see this link. I am not affiliated with them, just happened to read their blurb.

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

The Official Audiovox CCS-100 Install Thread

It took less time to do this install than it did to resolder (unsucessfully) my original amps ( I tried 2 of them) Works as well as the stock set-up.

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Mike
1983 Mercedes-Benz 300SD 270K
1960 Ford F250 62K
1990 Mazda Miata 156k

The thing is Bob, it's not that I'm lazy, it's that I just don't care.