I have a 50s Clark with all-contactor drive circuits. It worked fine, you could put the directional stick in forward or reverse and it would go that direction until you hit the brake. All good. Then I made the mistake of washing 50 years of grease out from the inside, now I have an issue with the movement contactors.
If I try to go forward with the directional stick, I have to reach down (with an insulated screwdriver) and push the relevant contactor manually. It then sticks and drives as normal. I hit the brakes, it drops the contactor and stops moving.
I'm assuming something is wrong with the coil, but forward and reverse seem like they're mostly separate, so I'm confused why both stop working at the same time. I'm guessing there's an interlock that prevents one firing when the other does, but I'm not sure.
I did pull a couple wires off the traction motor to clean up the contacts, but they went back on the same studs. And it rolls fine once I manually connect the contactor pads.
Any ideas for troubleshooting this, or a better wiring diagram than the one inside the cover that I can't read anymore?
S/N 14EA189
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Update: Well, at some point of messing with the switches, it seems to have sorted itself out.
On the negative side, it seems like I have a burning thing going on around what looks like a huge resistor underneath. I think it's cracked and might be bad now. Something it's doing that I didn't notice before is that the hydraulic pump seems to be on 100%, I don't think that's how its supposed to work, I think it's supposed to actuate the pump only when needed. I don't have much experience running this thing when it was working to know for sure.
So I've cleaned and tested a few things. First off, here is a link to a cleaned up wiring diagram on the inside of the contactor cover:
imgur.com/a/9ReVA (Copy and paste into browser address bar since I can't post a full URL link here)
I took apart and dried out the direction switch box pictured in that album, on the steering column. I also took apart and dried the brake switch (neither seemed wet, but still gave them a good shot of air).
I tested from terminal 13 on the terminal bar to the bottom (feed side) of the directional switch and get continuity when the brake is not depressed, open circuit when it is depressed which presumabaly breaks the contact, and this works as promised.
Under each contactor is a 4 terminal block that varies it's resistance depending on if the DS is in forward or reverse. If in Neutral, each measure 83 Ohms on the top right terminal, which drops to 40 Ohms if the respective direction is chosen on the DS.
I have no idea what resistance I should be seeing at each terminal except for the obvious GND and +ve closed circuits. I'm inclined to think something is wrong in these latches but no idea what and why both at the same time.
I can't seem to find this Master Switch that is referred to in the diagram, and I'm not sure how it would affect the operation anyway since I don't see any connections to the directional contactors.
good point brewski
some models did engage the dir contactor when directional was selected first.
So yes check directional switch also
If both forward and reverse are not engaging at start up, check the directional switch supply. Do the directional normally close after you select direction or after you press the accelerator pedal?
i would check the start switch in accelerator box/assy, it may have got wet and is now not working correctly.
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