Inside the box: VDO Cruise Control Actuator - PeachParts Mercedes-Benz Forum

michael cole · #1 04-15-2012, 03:43 PM

the reason my cruise is not working.with 12v across the pins to the actuator i can hear the motor spinning and i can actuate the solenoid but its been in there for 25 years.i thought a look inside might be prudent.i have replaced all the caps on the CC board as per James instuction.the rest of the board looks pristine.no charcoal.i have tried a spare board to no avail but cant verify if its any good.i have tested all the pin outs on the board while installed in the car to see if signals are present from the column stick and brake pedal.i have tested the brake switch and it is good.yesterday i cleaned up the left rear stop light assembly,replaced the bulb and cleaned all the grounds which show no abnormal amount of omhs.the history is the cruise was working albeit intermittanly and with some surging.then it just cut out.that was it

Bio300TDTdriver · #2 04-15-2012, 04:47 PM

If you remove the washer fluid tank you may be able to get to it.

JamesDean · #3 04-15-2012, 10:29 PM

Quote:

Originally Posted by michael cole

the reason my cruise is not working.with 12v across the pins to the actuator i can hear the motor spinning and i can actuate the solenoid but its been in there for 25 years.i thought a look inside might be prudent.i have replaced all the caps on the CC board as per James instuction.the rest of the board looks pristine.no charcoal.i have tried a spare board to no avail but cant verify if its any good.i have tested all the pin outs on the board while installed in the car to see if signals are present from the column stick and brake pedal.i have tested the brake switch and it is good.yesterday i cleaned up the left rear stop light assembly,replaced the bulb and cleaned all the grounds which show no abnormal amount of omhs.the history is the cruise was working albeit intermittanly and with some surging.then it just cut out.that was it

Can you post the part number on your amplifier box? I can look it up and make sure that you've got the right box.

Did you re-solder all the contact points, that also helps.

Are you having any speedometer problems? Bouncy needle,etc? The 124s are mechanically driven speedometers, a problem like that might cause inconsistencies/oddities in the output of the hall-effect sensor and confuse the cruise control.

michael cole · #4 04-16-2012, 07:15 PM

there are 2 #s on the box 004 545 2432,412 205/7/8 production date 12/87.i have done no soldering on this board except for changing the caps.the speedo shows nothing unusual.i tried to measure the output of the hall sensor at the amplifier whilst the car was at rest no voltage either ac/dc but as i drove the car a voltage seem to be generated but a precise reading was difficult.i assume because my DVM is limited.thanks for your help so far

JamesDean · #5 04-17-2012, 01:53 AM

Quote:

Originally Posted by michael cole

there are 2 #s on the box 004 545 2432,412 205/7/8 production date 12/87.i have done no soldering on this board except for changing the caps.the speedo shows nothing unusual.i tried to measure the output of the hall sensor at the amplifier whilst the car was at rest no voltage either ac/dc but as i drove the car a voltage seem to be generated but a precise reading was difficult.i assume because my DVM is limited.thanks for your help so far

The part number is correct for the 300TDT.

It sounds like your hall-effect is working, at rest nothing is generated as it will only generate when the speedometer cable spins. It will show a varying number as the cable will spin relative to the car's speed.

Try using some stripper and remove the conformal coating on the PCB, then solder every contact point.

When you installed the capacitors, did you be sure to observe proper polarity?

michael cole · #6 04-18-2012, 08:28 AM

ill take a good look at all the solder points on the board with a magnify glass.so your saying strip the coating right off the bottom of the board?is there any one particular area that could be involved?id love to get hold of schematics and associated theory of operation.give me a car i can tinker with and im happy.