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Overdrive Relay - A New Day
Well, a new day and we still don’t all know for sure just what the relay terminals are and what they do. It is time to do some creative poking around and figure this out once and for all – then we will be “authorities” on the subject. We can awe folks with what we know about an ancient and elusive secret. Our wives will think we are geniuses. Yeah, sure …. .
I suggest that we do some off the vehicle testing. Bring the relay to the bench or kitchen counter and gather up a meter, a couple of clip leads and one of those big square 6-volt lantern batteries. If you have a 6-volt vehicle, one of those batteries comes in as handy as a half-inch box end wrench many times. You can test this or that without trying to connect up to the vehicle battery.
IF, and notice that I highlighted IF, we have the relay we think we do - it is a simple single pole, single throw relay with a 6-volt coil and normally open contacts rated at about 15-amps or so. It’s a big relay, but in no way is it exotic.
Use your meter to find the two contacts that have continuity between them. I would guess that the resistance of the relay coil would be about 10-12 ohms, but that is just a guess. It won’t be zero and it won’t be several thousand.
Using the clip leads, connect the battery to those two terminals. You should hear the relay armature clunking on and off. Once you get the “clunk”, we’ve found the coil of the relay. Those are the TH and IGN terminals of the relay.
The other two terminals will be the BAT and SOL terminals. Everything I see anywhere says the BAT terminal has the fuse tied to it. Use the meter set up to measure continuity or low ohms and verify that when the relay armature goes “clunk”, the fused terminal connects to the remaining terminal.
Now, if this doesn’t happen, we have a different relay than anything I’ve seen described in the literature or something is bad. Once we figure out just what is where on the relay, we can move on to looking at something else if needed.
A picture of the relay would be a help, and of course a picture of the Jeepster!
Hang in there, we’ll figure this out too.
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Overdrive Relay- Close of Day 2
The pictures show a lot of info I was wondering about. It helps that you have a replica original wire harness. Hopefully whoever did the harness made a faithful copy, including wire colors.
In the picture of the relay on the fire wall, there is a red wire with three white tracer strands. That is a fairly heavy wire. In the wiring diagram I scanned and sent you, on p. 149, the wire identified as “Red-3 White trs” goes from the battery terminal to the upper left corner of the relay in the illustration. That is the terminal with the fuse on it. Incidentally a “Red – 3 White trs” goes to the upper terminal of the voltage regulator as well. “Red 3-White trs” is the color code for a primary battery lead. Red- 3 White Tracers is the BAT lead.
There is another wire, Blue with 2-white tracers. That is the wire corresponding to the SOL wire in the wiring diagram.
I see a green wire, I cannot see what the tracers are, connected to the relay. In the diagram the green wire with 2 blue tracers should go from the (–) side of the ignition coil to the bottom terminal of the kickdown switch. It should not be connected to the relay.
On the left lower corner of the relay is a wire that looks yellow(?) with multi-colored(?) tracers. I can’t find anything like that in the wiring diagram. Did a wire list come with the job? See if you can find a Yellow – whatever wire in the list and see where it might go. The guy who put the harness in my ’48 wired some things together that got wires really hot – fortunately nothing damaged.
One of the Jeep rules – trust no work that someone else did before you got the vehicle.
What I don’t see are a couple of black wires with 2-white tracers. One would go from the (+) side of the coil to the IGN terminal of the relay, the other would go from the relay (TH) to the kickdown switch. Is there an extra wire on the + terminal of the coil?
Just looking at pictures, I would guess that you have the relay shown on the right, the one called “Overdrive Relay 1948 to 1955”
Here would be my guess at terminal layout and wire colors:
TH IGN
(Black, 2 wht tracers) (Black, 2 wht tracers)
BAT SOL
(Red, 3 wht tracers) (Blue, 2 white tracers)
That attempt at a diagram didn't turn out well ... stinkin' editor tool ...
I can’t explain the odd continuity from BAT to TH. Internal failure or damage? I'd be about ready to carefully pry the case off and take a look inside to see just what is going on in there.
I would suspect that the 6V on the case was just someone’s way to identify that as a 6-volt relay. And, oh by the way, I really like the color! It looks familiar...