Voltage on frame.

[ab46501]

In the process of changing out a headlight bulb I accidently found out I have voltage running through the cart itself. The bulb was only connected to the negative and was hanging down and touched the cart and lit up. I checked with my meter and sure enough had about 38 postive volts running in the frame.

My motor recently overheated so I assumed that was where the problem was and I unhooked the motor from the controller. Sure enough the voltage dropped but only down to 10 volts?

One other thing I found and I don't know if it is normal or not but I have voltage on both sides of the solenoid as well.

All this is happening with the key off and the FNR in neutral. This is a 1991 36v Marathon series cart.

[chloe]

Since it's a metal body cart. I'm guessing someone direct wired something to the body thinking it was a grounding conduit. Get a copy of a proper wiring diagram and start tracing wires. The cart should have no power in the body/frame at all. Might tickle a bit when you put your foot down to exit! :)

In re-reading, I think I would start with the lighting. Most likely they wer not factory original items.

[razor1]

If someone used automotive lights on the cart that would be where I would start. Usually those lights ground to the frame and if they're not altered the mounting hardware will ground everything to the frame. Remove the lights and see if you still have voltage on the frame.

[JohnnieB]

The good news is that having a positive voltage on the frame means the frame isn't "grounded" (connected to B-).

Car type lighting fixtures can put B+ on the frame when the lights are on, or maybe all the time if the lights are wired with B+ on the socket instead of the center contact.

Carbon dust from the brushes can create a conductive path between the studs the cables connect to and the motor case, which connects to the frame via the axles and springs. This is typical, unless the motor is new or recently cleaned. However, it is a high resistance current path and won't pass much current (Micro and Milli Amp range), but can be measured with a DVM due to the high input impedance of the DVM.

The fact that a light bulb lit, indicates a bare wire, or something similar, is touching the frame someplace. Leave the cable(s) off the motor so you only have the 10V and go looking for where the 10V is coming from.

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There is a 250 Ohm resistor across the solenoid contacts, so voltage will be measured on both sides of it. You should get full battery pack voltage on the battery side and 3-5 volts less on the controller side.

[ab46501]

Thanks for the replies. I wired the cart myself and installed the lights. Lights run thru a 36 to 12v converter. Nothing was wired to ground on the frame.

I did unhook the cables from the motor and the voltage dropped to 10v. This was right after charging. Over the weekend the voltage dropped down to about 6.5v which makes me think it is one battery someplace.

I thought it had to be a bare wire too but this really has me scratching my head because the wiring is all heavy duty 2/0 gauge cable reaplaced just a little over a year ago. With running my hand over each one and visually inspecting them I cannot feel or see a problem.

I have checked every wire and unhooked the pack from the motor, controller and all other accessories. I guess the only thing left to do is unhook all the batteries from each other and test each battery idividually.

[razor1]

Check your battery tiedowns if you're getting exactly 6.6 V it may be that a bare wire touching the tiedown and transferring the voltage to the frame

[gornoman]

Dirty batteries can allow voltage to leak to the frame. Keep them full, charged, and CLEAN.

[ab46501]

Originally Posted by gornoman

Dirty batteries can allow voltage to leak to the frame. Keep them full, charged, and CLEAN.

Good call. What fried the motor was my 13 year old son riding it hard in the mud. I cleaned the mud off the batteries and bingo......no more 6.5v on frame. Thanks!

I still have full pack voltage on frame when motor is connected but a new motor should fix that.

[simple man]

Originally Posted by ab46501

Good call. What fried the motor was my 13 year old son riding it hard in the mud. I cleaned the mud off the batteries and bingo......no more 6.5v on frame. Thanks!

I still have full pack voltage on frame when motor is connected but a new motor should fix that.

Beware of that because a full short in your motor can be very expensive! It is possible to burn out the controller!

[ab46501]

Yeah I am not running the cart and have the motor disconnected. Good advice though.