After getting the overdrive working on the BN4 last week, I felt like I was on a roll. So I went after the non-operational overdrive on the BJ7, a partial restoration that I finished a couple of years ago. The drive train was in the car, although all the body panels, interior, and trim were off of it when I got it. Although the car was repainted and reassembled, it bugged me that the overdrive did not work.
The third reason why the overdrive did not work involved the Overdrive Switch, which I replaced today. Interesting how Healey mounted the Gearbox Switch externally on the center shift BJ7, compared to how it mounts on the earlier side shift cars. That makes it easy to see how it works. The switch still made contact to complete the circuit, sort of; the gear shift lever had to be pushed sideways a bit in 3rd and 4th to make it engage and there was no adjustment left.
That was after setting the Throttle Switch, which was way out of adjustment. And whoever installed the overdrive solenoid just dropped the new plunger in from the top, instead of taking the cover off and fitting it into the right place.
Overall, not a difficult fix. Just glad that the unit did not have to come out.
Three reasons why the overdrive did not work. Now it works fine.