Getting the overdrive wired and functional is one of the last big hurdles in finalizing the installation of my new B20/M41. The car is perfectly drivable as-is, but I'm just now getting to integrating the OD.

I'm trying to utilize the blue "sequencing" relay from a 240 as well as "pull to flash" function of the indicator stalk as the momentary switch. Ron Kwass and others have both posted very helpful schematics for this setup, which I am trying to duplicate. The only thing I have NOT wired in as of yet is the indicator light.

I have not taken the car out on the road yet. I just have it on stands in the garage. The 4th gear switch, OD solenoid, and relays are all new parts. I've verified with the multimeter that the 4th gear switch has continuity when in fourth, and is open in all other gears.

With the car in fourth gear (not running), when the stalk is pulled, I hear the relays click over and hear the "thunk" of the D type OD solenoid firing. Seems like normal operation.

If I then pull the stalk again, I hear the relays only. I assume this would be the expected result for deactivating the OD. Pulling again (reactivating OD) gets another "thunk". Again, all seems well here.

If I start from forth gear, engage the OD ("thunk"), then shift to any other gear, then BACK to fourth, pulling on the stalk gets another "thunk". This would be consistent with my understanding of how the system should function (OD is deactivated when leaving 4th, needs to be reengaged via switch when returned to 4th).

The last situation is the confusing part for me. I can hear the relays click and the solenoid "thunk" in 1st, 2nd, and 3rd gears as well. However each time the stalk is pulled, the result is the same (unlike the "on/off" sequence in 4th gear). It seems like the 4th gear switch should be prohibiting the solenoid from firing in any gear other than 4th.

I'm planning on getting the indicator lamp wired up this evening so I have a better idea what is going on. Any ideas why I might be "allowed" to engage the OD in any gear, with a known good switch, and wiring that has been triple checked?