Author Topic: Need some non-W116 technical advice  (Read 248 times)

ptashek

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Need some non-W116 technical advice
« on: 20 December 2018, 02:06 PM »
Over my years here I've learned to rely on the scary amounts of Benz related knowledge you folks bring in, so before I go searching even deeper on other sites here's a question - does anyone happen to know if it's possible to test the electronic throttle actuator on a W124 off-car? If so, what's the inputs it is expecting - especially the actuator motor. I know the inputs it's supplying to the ECU, so that's not an issue.

I've had trouble with mine - the usual, crumbled insulation - and replaced it with a new VDO part, but have since rebuilt the old one and now just need to test it before I declare success and call it a day.

What's confusing me is that the actuator motor is just a dumb DC motor with a 30deg, physically limited, range of movement. If it were a servo I'd give it a DC power supply and a PWM signal to control speed and direction, and off we go. I'm guessing it has direct PWM drive from the ECU, and works in an on/off fashion rather than continuous control. There's a ton of information on how to rebuild one of these (which is dead easy), but none on how to test them other than putting it back on the car which I can't do.

I was hoping to build a test rig on top of a micro-controller.

The part number is A0001416525, non-ASR M104 - as seen below during the rebuild.
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)
1977 "Milan Brown" W116 350SE (parted out)

ptashek

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Re: Need some non-W116 technical advice
« Reply #1 on: 20 December 2018, 03:27 PM »
...and while I was re-reading what I've written, the "you dumbass" bulb went on. It might be a dumb DC motor, but it works in a closed loop system using the throttle plate position sensor as an input into the ECU, which in turn controls the PWMed supply voltage. So, unlike a typical RC servo which integrates all of that, here it's done in the ECU.
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)
1977 "Milan Brown" W116 350SE (parted out)