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Thread: Overdrive relay

  1. #11
    Junior Member capyjack's Avatar
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    Well, I couldn't stand it and had a few minutes.
    The only terminals that have continuity on this relay are on the same end of the thing and one of them has the fuse.
    So, I am thinking that maybe the fuse is on the (IGN) post of the relay.
    So I hooked those two up (TH and IGN (to the fused terminal))as suggested and the remaining two on the other end of the box also.
    At least now I don't get a click when I hook the battery up.
    I also don't get any reaction when I turn the key on. The rail switch is closed, all I did was put the ohm meter on it so don't know if there is any voltage there.
    Is this a good thing?
    Does the governor have to be spooled up to provide a ground to the solenoid to trigger the relay?
    So maybe I wont know if its working until I drive it again?
    Would a good test be to hook a ground to the governor lead to see if the relay activates?
    Sorry if I am asking stupid questions but having the thing wired up and being able to hook up the battery is kind of a big change here.

    I should also add that I picked up this car as an unfinished project, it had been rewired, the OD harness was not dealt with however, but was included, the relay was missing.
    I am pretty sure that I have the OD harness installed correctly now as there were pretty good instructions for that included in the boxes of parts. Also a new kick down switch which works as it kills the engine if I floor it.
    If I could get comfortable with the wiring installation I would hope that the OD would activate.
    If it doesn't then I will be doing more trouble shooting, I see this as fairly simple puzzle but this unmarked relay has been throwing me.

    Thanks again, Jack
    Last edited by capyjack; 10-31-2018 at 05:16 PM.

  2. #12
    Super Moderator LarrBeard's Avatar
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    You asked:

    A.Would the (TH) and the (IGN) as well as the (SOL) and (BATT) typically be on opposite ends of the relay as you illustrate?

    Close, but not really. Here are two configurations of relays from Willys America.

    https://shop.willysamerica.com/Overd...y-p/916721.htm

    BAT is the terminal with the fuse. TH and IGN seem to be opposite each other at opposing ends.

    B. Also, does the relay need to be grounded to function properly?

    No, none of the terminals is a ground and the metal case is only a mechanical mounting bracket.

  3. #13
    Super Moderator LarrBeard's Avatar
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    Overdrive Relay

    We are crossing emails and asking a lot of questions too fast for my old brain to handle. Before this morning I had no idea how an overdrive worked so I can’t claim to be any kind of authority after just a day of looking. I have looked at Studebaker and Kaiser-Frazier/ overdrives and they look a lot alike. Here are the things I can say with some degree of certainty.

    A. The terminal with the fuse is the BAT terminal. That ties directly back to the battery and has no other overload protection so the fuse is in the high current path from the battery to the solenoid. The fuse is a 20-amp fuse; it is in the solenoid-battery circuit. The terminal with the fuse is neither TH nor IGN.

    B. The vehicle has to be moving for the switch contacts in the governor to close.

    I am enclosing scans of the three pages from the Willys-Overland Shop manual that speak to truck overdrive operation.

    Examine the wiring diagram on page 149 to see the three circuits that control overdrive operation.

    We really need to see a photo of your relay if we are going to get much further.
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  4. #14
    Super Moderator gmwillys's Avatar
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    I agree with LarrBeard. Four wheel drives do not use the automated overdrive units, so this is a new subject for most of us. I know I as well have never looked into how and why the system worked, although it seems fairly straight forward. Testing will require driving, because the overdrive will not kick in until 30 MPH is attained. There are several things that have to coordinate with each other before the overdrive will engage. Once you have everything dialed in, it should work fine. Education by trial and error tends to be the best way to learn.

  5. #15
    Super Moderator LarrBeard's Avatar
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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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  6. #16
    Junior Member capyjack's Avatar
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    OK, I have been spending some time here and I am finding that the only two terminals on the relay that have continuity are the one that has the fuse (batt) and the (TH) terminal.
    Earlier suggestion was that the continuity should be the IGN and TH.
    If I hook the hot wire from the battery to the fused terminal (and other wires accordingly) the relay activates as soon as I hook up the battery.
    Therefore I switched the wires from the battery and the ignition on the relay.
    I drove the car and still have no OD.
    However I am getting some clicking at the relay once in awhile by turning on the ignition.
    So lets assume that the main feed to this relay wants to go to the IGN post suggested in the image and the switched feed goes to the fused post on the relay.

    The trouble shooting page in Jeepster Mechanics manual says to check that the governor wire be "hot" with the ignition on and the OD lever pushed in. The governor lead is not "hot" when I do that.
    I was under the impression that the governor supplied a ground when it is spooled up so I may not be understanding this. It also could be that it does indeed supply a ground to the solenoid which in turn sends power to the relay to activate it.
    This is where I am confused.
    I am hoping that I can attach the info that the vender supplied as well as the pics you guys have been asking for.
    The "6V" was written on the relay when I got it.
    Where you see the "sol" and "ign" I wrote on there from the info in the first image, which is supplied by the vender for the 12 volt unit.

    I very much appreciate the help here and I am in hopes that your wives will consider you to be geniuses. I don't have one so I just want to impress myself.
    Thanks, Jack
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  7. #17
    Super Moderator LarrBeard's Avatar
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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...
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  8. #18
    Junior Member capyjack's Avatar
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    Thanks for this Larr.
    It will be a week or so before I can get back to this.
    I kind of thought that I may have a bad relay. I bought it from this site KW even though it cost a hundred more than the competition.
    I doubt that it has any kind of warrantee as its electrical and I have tried several installs.
    Taking at apart will certainly cost me $250. However that would be worth it if I could get the stupid thing to function.
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  9. #19
    Super Moderator LarrBeard's Avatar
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    Wow! I really like the two tone red. Nice Jeepster.

    If you look at the case for a while, I'll bet you can figure out how to get the can off without hurting the innards. It may take a couple of slits around the edge of a crimp to get some pry room. I'll bet it's built on a insulation base with the lid just as a cover.

    I've done that with the original bimetal oil pressure sensor on the '48. I used RTV sealer to close it back up.

    Oh, by the way, on the truck the primary battery leads are red with 3 white tracers too.

  10. #20
    Junior Member capyjack's Avatar
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    LARR said - Use your meter to find the two contacts that have continuity between them.
    OK, I have continuity between the SOL and IGN terminals as well as continuity between the TH and BAT terminals.
    Applied voltage to the TH and BATT makes the click. The SOL and IGN is more like a short.

    LARR said - Those are the TH and IGN terminals of the relay.
    But one is clearly the fused terminal.

    My Jeepster manual suggests that there be voltage at the governor lead when the OD is turned on. I don't have any voltage there so I cheated some voltage to it and the car drives locked into overdrive. (side note: the car wont go into reverse this way)
    Back to the trouble shooting section. symptoms', "Relay clicks at idle or as soon as ign. is turned on. Vehicle is in overdrive from a standing start. Impossible to shift into reverse. Impossible to pull out of overdrive plunger. Impossible to tow or push"
    My relay clicks when I hook up the battery, also sometimes clicks when I turn the ignition on.
    Manual "probable remedy" "Short or ground in relay control circuit. Check wiring, relay, kickdown switch, rail switch and governor for short or ground. Faulty governor. Replace. Faulty relay or solenoid. Replace.

    Needless to say I am very suspect of this relay that I paid KW $250 for.
    So I took it apart as suggested. Knowing nothing about these it all looks good, No smoked wires, no bad smell, all looks new,
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