7 car Cottrell trailer, electric pto

Got a 7 car Cottrell trailer, self contained 12v PTO.

Battery is always dying, and when I jump it to the tractor battery box (because time is money) the negative gets hot enough to melt thick cables.

Come to think of it, it works the same way if I only jump the negative terminal, so I'm sure the positive is connecting right.

I have checked the ground connections and all the visible wiring. No problems seem to present themselves there.

My question is this... Is there any place in particular that I should be looking? I know every type of trailer has their problem areas, and if anyone out there knows where inside this particular type of trailer I should check, I'd be happy to know about it. It's the easy loader model.

Thanks everyone.
 
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Duck

Quack
Supporter
Battery is always dying, and when I jump it to the tractor battery box (because time is money) the negative gets hot enough to melt thick cables.

Come to think of it, it works the same way if I only jump the negative terminal, so I'm sure the positive is connecting right.
Are you saying that connecting a cable from tractor battery negative, to trailer battery negative, melts the cable?

:headscratch2:
 

Hammer166

Instigateur №166™
Supporter
Sorry, been a bit busy. Does the trailer have both a hot and ground running to the truck? And melting the cables, is that while running the pump, or just sitting there?
 
I'm not sure. I know it uses the 7 pin as well as a separate single pin cable run from the rig.

The negative heats up the jumpers to a melting point during operation of the PTO (on/off switch engaged and any set of pistons pushing up). When at rest, nothing.
 

RamblingPete

Well-Known Member
Could be two things . One is there's no restrictor between battery and switch , which in that case I'm surprised switch isn't burning out prematurely. So that means the electric solenoid running the pump is likely going bad . In many ways it's like a starter ... it to will heat cables and kill batteries in same way when going bad .
Guess third possibility is a bad ground but with that kind of heat you'd see where it is because it would at the least give a puff of smoke .
 
This was happening with both the old and new solenoid (yes, I thought it was this too, so I had it changed).

The mechanic checked everything out, said he had no idea where the problem was coming from.

I'm thinking there is some sort of short coming from someplace unseen like in a design defect... And my mechanic is making every excuse in the book not to rewire the whole PTO/hydraulic systems.
 

Hammer166

Instigateur №166™
Supporter
It sounds like it's not grounding properly, so it's not charging the battery, and running all the current through the jumper cables.
 

Duck

Quack
Supporter
I'd try running the motor directly with jumper cables and see if they get hot.

Do it with the trailer unhooked from the truck so there's no ground path through the 5th wheel or the light cord. Make sure the polarity is correct. DC motors will run backwards if it's reversed and I don't know what that would do to the hydraulic pump, if it would blow out the suction side or something.
 
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