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TR2/3/3A Overdrive Sleuthing

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M

mmgwhite

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OK where would y'all start with this problem?
TR3A OD working perfectly, flawlessly, dependably and praiseworthy. Until yesterday.
Nothing, NADA, upon flipping the switch. Any gear, any speed.
Can't hear a solenoid clicking with the switch but have only tried that with it sitting quietly in my hangar and the electric
fuel pump may be loud enough to drown out a faint click.
I have visually inspected the wiring under the car and all looks OK
Oil topped up. Where to go from here??
Thanks in advance for ideas.
 
Get out the voltmeter/DMM and check the output voltage from the relay. If it is sending a good solid 12v to the solenoid, then it's time to pull off the tunnel. But if not (and you can still hear the relay click), most likely the relay itself is bad. I would double-check that the contacts are getting 12v in though, just on the wild chance that it's a bad connection (or blown fuse, I added a fuse to that line) somewhere else.

FWIW, I found that the relays last a whole lot longer with a solid state diode added as a snubber across the solenoid (although I mounted the diode at the relay). Now that I've had the contacts inside the solenoid go bad after all these years, I also added a diode inside to suppress the kickback from the pull-in coil, but it's really too soon to say if that will help or not. The theory is sound, though.

 
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