We just acquired our "new" 84 300SD this past weekend and I've been doing the routine checks and replacments and found out that my cruise control will NOT take hold until the speed is at least 50mph and was wondering if this is normal. My 82 300D turbo cruise takes hold at 30mph but I haven't found anything in the owners manual for it on this one.

I will be posting some pics this weekend of my WIFE's "new" diesel, when I have enough daylight after work to take them.

Not normal. My cruise will hold down to around 30mph too.

__________________
past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

Jake1222,
Unfortunately that is one of the signs of the Amplifier starting to fail. It should hold fine at 30 mph and up. My SDL was doing the same thing. A new amp cured it.

__________________
D. Blake
86 300SDL 340K (for sale)
83 300SD 205K (gone)
06 Chevy K3500 LBZ CCLB 50K
94 Chevy K2500 6.5L TD 250K (gone)

If you have to replace the amp, forget the new at about $350. I picked up a rebuilt from an outfit out of San Diego for $129 with a three year warranty. Works great!

Happy Motoring

RBM

I figured it was the amp. I've found some rebuilts with warranty for about $99. I may also just rebuild it myself. I am an electronics tech by trade anyways so I may as well do it myself like everything else on these two.

Thanks for all the replys.

Hi Jake.

You know the saying.


If you want something done right,you have to do it yourself.

Louis.

Hey, keep us posted on how that goes. I used to be a tech, but that was a long time ago,and have forgotten more than I used to know But I'm not afraid to dig into things.

__________________
past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

I purchased the CD that the guys at RepairFlix.com sell and it was well worth the $11 bucks I paid on E-Bay. Basically, to repair you just resolder the cold solder joints on the circuit board. They suggest doing ALL of them which takes a couple of hours, but if you're feeling lucky, just do the ones of the several largest components on the the circuit board. These tend to go first since they will be effected most by the deisel vibration. To get the board out of the silver box, just bend the metal tabs. There is no neat way to do this unfortunately.

I was also very lucky at my local bone yard and got a working amp for my 82 300D for $10 bucks, but this was unusual.

Good luck and let us know how you made out.

PS... this technique also is what they recommend for repairing the climate control unit and the tachometer sending unit (see my post on tachometer fix for a tool-free first try though)

__________________
Mr Goodfahrt (pronounced FAIRT... means "good trip" in German)

1982 300D Turbo Pastel Gray (off-white) 200k+(?)
newbie but willing

Jake1222,

If your cruise control works fine above 50mph than forget all the good and correct advice above. It happened to my car too.
When I acquired it about 15 months ago, the CC didn't work under 50 mph. The previous owner never used the Tempomat at lower speeds! As I started to use it on every speed, slowly it began to respond on lower speeds. After a few months it worked and works still as it should. For my W 124 it starts working at 40 kmh ( 25 mph ? ) and cuts out under 40 kmh.
I can easely feel it : if there is, say 70 mph in the memory and I engage it at say 10 mph, nothing happens. When I continue to accelerate slowly I can feel at 25 mph the "kick" when Tempomat takes over control. Mine is a 300TD turbo and I assure you : you feel it when she accelerating !
So with a little luck your problem will solve itself. It only will cost you a little patience!

Danny

I've gotten the amp removed this past weekend and opened it up without any problems. It was a rebuilt unit from a previous owner and from visual inspection of the circuit card I found three of the capacitors were looking a little burnt up. Underneath thier coating it was evident that they were leaking thier dielectric and now I am in the process of determining thier values so that I can order some if I need to or replace them if I already have them in my stash.

If anybody has the parts listing for these amps or schematics let me know and maybe we can work out a deal. I do have tools and equipment for soldering/desoldering and other test equipment available for most electronic equipment.

Hello again, Jake,

Take a look at this :

http://gdl-online.com/differences.html

http://www.mindspring.com/~houlihan/merc/cruise.htm

Danny