Constant Idle Lifting Magnet M129 Auto 250SE

[mylittlefintail]

Does anyone one know where the switch for the Constant Idle Lifting Magnet exist? Its the electro magnet that sits on the inlet manifold that is connect to the cross-rod over the engine. According what I've read when you put your car into drive the magnet is activated so as to counter act the drag from the automatic transmission so the engine doesn't stall.

The minute I turn on the ignition the magnet is activated. I've looked my column shift and even pulled the shifter lever out but the magnet remain constantly on? The wiring diagram says the switch should be somewhere on the column shift lever??? I can't see any wires??

The engine is a Auto M129 250SE in a W111 saloon. (YES I know it's not original but the 220 motor was gutless!)

Thanks
Moses

[Larry & Norma]

On an automatic pagoda it is switched from the auto gearbox. It is switched to ground i.e there is permanent volts on one terminal the other being switched to ground when it is put into gear. I also believe aircon if you have it will also switch it on.

[ja17]

Gnuface is correct. Earlier cars used the pressure switches on the transmission.  In later years a dashot was added to the USA cars and the A/C switch was used to activate the likage magnet

[tuultyme]

I had a similar problem when I first got my car.  The Constant idle switch was always on.  I discovered that the wire that went from the left transmission pressure switch over to the right transmission pressure switch was grounded to something.  I disconnected this wire but could not pull it out so I just feed another wire between the two switches and now it work as it is suppost to.

[al_lieffring]

The swith on the shift lever shown in your service manual would have been for the Hydrac automatic clutch models. The switch activated a vacuuim servo that disengaged the clutch whyle the (manual) transmission was shifted. Many of the 111 chassis cars came equipped this way. Volkswagen used this system too in thier automatic stick shift cars. 

[mylittlefintail]

Ah I've disconnected the A/C and not reconnected it as I've still not got round to re-gassing the system yet. Plus I did have an extra wire when reconnecting the auto transmission cables back up that I wasn't 100% sure where it should have gone. I'll give it all a try and report back my findings. 

Strangely enough I have driven a finnie with a hydrak transmisson in and thought it was very cool bit of engineering. I really didn't realise how rare that transmission was!!