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TR2/3/3A Overdrive Wiring

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ckeithjordan

ckeithjordan

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This is primarily for Geo or Barry, but anyone can chime in!

Several years ago, Randall Young (RIP) suggested adding two things to the overdrive circuit: 1) A in-line fuse (AGC 10 or 5) in the brown/white feed from the ammeter and 2) a diode to prevent to help absorb the inductive kickback from the solenoid.

If I understood him correctly on the second part, you would wire the diode at C2 on the relay (in addition to the yellow/purple wire from the solenoid) and a ground point. Is that correct? I was thinking about doing that, with a double spade plug to accommodate the diode and the Y/P wire, then tie to the screw holding the relay to the battery box underneath. He also said to "point" the diode to ground if +ve or to the relay if -ve. Is there a particular diode current rating I should be considering?

Thanks for any clarification.
 
Correct,the diode goes from C2 to ground -- of course 'from C2' means anywhere on that yellow/purple wire.

I did it along the way at a connector on the harness, substituting a double bullet for a single bullet:

J84wCaF.jpg


This is the diode I used (though by no means the only choice):

1wIXzkA.jpg


The wiring diagram showing the diode for a positive ground car:

X3F5jIp.jpg


Randall actually installed the diode on top of the solenoid, fitting it inside the rubber cap:

efk42iN.jpg


For the fuse I just put connectors on a fuse holder to fit it between the brown wire and its lug on the relay (C1):

b2NVrSL.jpg


WDomXRw.jpg


All I can offer is 'what I did' - no theory or tech explanation. I just followed Randall's instructions.
 
Same here.
This is how I did it. Works so far and the fuse let me know that the solenoid was not switching from pull in to hold in by blowing. Got a new solenoid.


Diode pack s.jpg
The diode I used. It looks smaller physical than Geo's diode.
OD wiring diagram s.jpg
Fuses and Relay.jpg
The 10 amp fuse is for the OD.

David
 
Be sure that the cathode of the diode--the end with the line around the diode's body--is connected to the solenoid, with the opposite end grounded. If you get it wrong, you'll find out really fast, but it may take a while to get the burned smell out of the car.
 
Sarastro said:
Be sure that the cathode of the diode--the end with the line around the diode's body--is connected to the solenoid, with the opposite end grounded...
Click to expand...

That is true if the car is negative ground. The OP has a TR3 which will be positive ground unless it has been changed.
 
Yes, my car is negative earth, so the cathode end is pointed to the relay at C2, with the Y/P wire.
 
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