In this thread http://www.peachparts.com/shopforum/tech-help/315339-inside-box-vdo-cruise-control-actuator.html over in the gas forum, JamesDean shows how to disassemble and test a cruise actuator.

I went through the testing steps and determined mine was showing open circuit between pins 4-5 which is the motor winding. Normally the problem is excess current; my problem turned out to be zero current, infinite resistance, and no motor action at all.

So following JamesDean's photos, I managed to get the actuator opened up. I discovered that the reason for the open circuit on the motor is that one of the leads from the motor brush holders had broken off the printed circuit board.

Unfortunately this is on the "back" side of the actuator and can only be seen by removing the "can" that protrudes out the back side. The solder pad is on the back of the circuit board and so cannot be accessed from the front (the side exposed by removing the cover through which the shaft protrudes).

The motor is a permanent magnet type, so there is no field winding. There are strong magnets inside the "can". Pins 4 and 5 from the cable go directly to the brushes and energize the armature winding directly.

Has anyone (Army??) taken one of these apart far enough to remove the motor armature, solenoid, and pc board completely from the housing? I cannot see how to remove it without fear of damage.

I grabbed another actuator from another 83 240D at a p-n-p that has the exact same symptoms, so I do have one to practice on. However I would rather not trash an otherwise good actuator trying to figure out how to get it apart.

I tried to reply with my situation to JamesDean's thread, but got no responses after several days. I also tried PMing JamesDean but he had only gone as far as what was shown in the thread. So I am serving this up on the Diesel forum...in case someone who knows missed it over there on the gas forum.

If I get this figured out I promise there will be pictures...I suspect that this may be the cause of many dysfunctional actuators and it would be great if they were easy to save.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Do you need to contact JamesDean? I have recently been the beneficery of his fine expertise. My 1988 190E which I converted to a D with a 2.2 dsl. engine lost it's cruise amplifier. He directed me through the trouble shooting, I ended up swaping out the amp. and am now up w/cruise again. He knows his stuff on these units. Very fair and prompt to deal with also.

Yes I have contacted him, unfortunately, he has replied that he has not taken his further apart than what he shows in the pictures in his post above.

I have to take it completely apart in order to fix what's wrong with it and I don't want to break something trying to take it apart.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech