I need a sanity check before I start using this circuit on a daily basis.

First, the back story is that I have a 140 with and M41 that has a relay-less system I wired myself. 12V to a column switch which then goes to the 4th gear switch, and finally to the relay. The column switch and 4th gear switch both have to be closed to complete the circuit and give the solenoid 12V. Very simple, and has been working great for 2 years.

Now, moving to my rebuilt 242. I have the old style slider switch and wanted to wire a similar system without a relay. For the most part, it works the same, except that I have a grounding 4th gear switch on the M46, not a pass through.

So, to compensate, I have 12V going to the shifter switch, then directly to the solenoid. The ground side of the solenoid goes to the 4th gear switch. Thus, 2 conditions still have to be met to complete the circuit; the shifter switch and 4th gear switch.

I have heard that not using a relay requires the inclusion of a reverse biased diode across the solenoid terminals, but I don't know why. I certainly don't have this on my successful 140 design.

Does anyone see a problem with this setup on the 242 as it stands? I haven't yet tested this or driven the car.