[TR] Perplexing A-Type OD Problem

Bill Brewer billbrewer59 at yahoo.com
Fri Jun 26 19:59:51 MDT 2020

Hi Listers,

     I was on a trip driving my TR3 that has a TR4 overdrive trans in it.
The OD had been working fine and then suddenly nothing would happen when I
threw the switch. I checked the relay with a test lamp and the C2 output
terminal (yellow/purple wire) lights up fine but the solenoid wouldn't
actuate. I tested the solenoid (Moss - aftermarket) on my workbench and it
seems to pull in fine. It probably only has 5,000 miles on it and looks
almost new. I put it back in the car and it doesn't actuate. I ran a new
wire straight from the C2 terminal on the relay to the installed solenoid
and it still doesn't actuate, although I can move the actuation lever by
hand. Evidently the solenoid is bad again. It seems like I go through OD
solenoids fairly regularly. Randall (does anyone know how he is doing???)
had me install a small "bounceback resistor" on the from the C2 output
terminal on the relay to ground to eliminate bounceback voltage spikes. Any
idea why I would be going through solenoids so regularly? I seem to change
them out about every 10,000 miles.

     Could it be a grounding issue for the solenoid? It seems like there
would be plenty of electrical continuity from the transmission to the engine
and chassis, so that shouldn't be it.

     Thanks in advance,


     -Bill Brewer

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