Dear Chuen
I think that the mechanic that told you that, did not consider one electrical control issue which is important on the pagodas. That is the fact that automatic transmissions for mechanical fuel injected cars, provided some signals to the fuel injection system to increase iddle speed if the engine was about to quit. (stalling).
There is a connection strip terminal with 4 wires on the automatic transmissions, designed to work with Mercedes mechanical fuel injected cars control logic. That connection block has the following signals, which for sure were not present on a w123 since the control approach was absolutely different:
1. Iddle switch positive signal. Active whenever throttle butterfly at intake manifold is clossed
2. Low transmission oil pressure, trigger signal for the iddle increase selenoid (negative signal)
3. Kickdown signal (for sure this one should be present on a w123)
4. Ground
I work a lot on wiring harnesses, and love also to produce practical solutions for classical Mercedes Benz owners.
I have been asked once by a customer to fabricate a wiring harness to convert his Manual transmission w113 to automatic as per original design.
Since that request, I have made that product standard on my listing on
www.wiredoktor.com web page.
See here the link to that:
https://wiredoktor.com/products/mb-w113-manual-to-automatic-harness-conversion-kitBest regards
Eng.Leonardo Peterssen
Classic car owner and CEO for
www.wiredoktor.com