Marathon 36v Jerks repeatedly but does not go. I think it is the motor.

biphase · 07-09-2020, 01:58 PM

[QUOTE=kevinclark93;1738621]Alright I have another set of batteries that were reading 38 volts that I jumped over to the existing battery pack in the cart and I am getting the same result with the tires jerking. As mentioned before the studs coming out of the motor are a little loose is that normal.[/QU

When you measure battery voltage while the cart is jerking, you should attach your voltmeter directly to the B- and B+ blades on the controller. Measuring at the controller will take into account any voltage drops in the cables or possibly burned contacts in the solenoid.

If it is not a battery issue, I probably can't help you. I am not an expert on motors but I suppose it could be a motor problem like bad brushes or a fouled commutator. Perhaps others on this thread may have some other suggestions.

kernal · 07-09-2020, 03:14 PM

Quote:

Originally Posted by kevinclark93

Alright I have another set of batteries that were reading 38 volts that I jumped over to the existing battery pack in the cart and I am getting the same result with the tires jerking. As mentioned before the studs coming out of the motor are a little loose is that normal.

No!! You need 2 wrenches. Take the top nut off and tighten the bottom one and hold it there with one wrench and tighten the top nut with the other. May want to remove the motor and check for internal damage.

kevinclark93 · 07-10-2020, 08:28 AM

Quote:

Originally Posted by kernal

No!! You need 2 wrenches. Take the top nut off and tighten the bottom one and hold it there with one wrench and tighten the top nut with the other. May want to remove the motor and check for internal damage.

Does the armature just slide out or are there some tricks to it?

kernal · 07-10-2020, 08:57 AM

Armature is supported on one end with a bearing (brush/commutator end) and other end has the splines that fit on the shaft on the cart. You can't really bench test because you would need specialized equipment.
I can't advise you on motor repair. If it were me on a motor that old I would take it to a shop with capability to service it or just buy an new, better one. But that's because my interest in DIY repair is very limited.
There are people here who have done some motor repair. Hopefully they will comment but if they don't you may want to start a new thread specifically for motor repair to get their attention.

Bama Brad · 07-12-2020, 11:08 AM

Quote:

Originally Posted by kevinclark93

Okay I am looking for a sanity check. I have an old marathon serial no 542608 and manuf. code H13893. It is new enough to have a controller, but not sure of the year.

If you hit the gas in forward or reverse the tires will rotate a few degrees and then bang and then rotate again repeatedly in a jerking motion. The tires will do the same thing off the ground on jack stands. It sounded like something mechanical so here is what have have done.

- Pulled the differential pan off and everything looks good. Nothing stripped and no shavings. Everything works as it should if you spin my hand.
- Pulled the motor off and the spline gears look good. There is a classic burned smell from the motor. If I spin the input shaft of the differential by hand the tires spin as they should.
- At this point I think it is the motor. I un-wired the motor and jumped it with jumper cables to rule everything else out. The results were the same tires spin in a jerking motion a few degrees at a time.

I want to get a sanity check that it is the motor before I buy a new one. The motor is series wound. Also as a side note when removing the cables from the motor the studs spun and that cant be good.

Thanks in advance

Have you looked at outer spines (behind brakes)?

kevinclark93 · 07-13-2020, 03:24 PM

I have not looked at he wheel splines. It is a possibility but I figured they would still spin the tire off the ground as opposed to jerking. I can also spin the tire and back drive the motor so it seems they are transmitting torque, but probably worth checking.

There has to be a check to condemn the motor before I go buy a new one. I guess my next move is to take it apart and check the windings.

JohnnieB · 07-13-2020, 08:09 PM

Series motor check. Wheels off ground.

kevinclark93 · 07-14-2020, 03:04 PM

Quote:

Originally Posted by JohnnieB

Series motor check. Wheels off ground.

I did that test with the same result. Wheels jerking off the ground.

JohnnieB · 07-14-2020, 03:56 PM

Quote:

Originally Posted by kevinclark93

I did that test with the same result. Wheels jerking off the ground.

Time to open the motor.

Bama Brad · 07-14-2020, 04:52 PM

OHH No! I hate it when he says that

07-09-2020, 01:58 PM	#11
biphase Gone Wild Join Date: Jan 2009 Location: Ocala, FL Posts: 384	Re: Marathon 36v Jerks repeatedly but does not go. I think it is the motor. [QUOTE=kevinclark93;1738621]Alright I have another set of batteries that were reading 38 volts that I jumped over to the existing battery pack in the cart and I am getting the same result with the tires jerking. As mentioned before the studs coming out of the motor are a little loose is that normal.[/QU When you measure battery voltage while the cart is jerking, you should attach your voltmeter directly to the B- and B+ blades on the controller. Measuring at the controller will take into account any voltage drops in the cables or possibly burned contacts in the solenoid. If it is not a battery issue, I probably can't help you. I am not an expert on motors but I suppose it could be a motor problem like bad brushes or a fouled commutator. Perhaps others on this thread may have some other suggestions.

07-10-2020, 08:57 AM	#14
kernal Gone Wild Join Date: Jul 2010 Location: Peachtree City, Ga. Posts: 2,759	Re: Marathon 36v Jerks repeatedly but does not go. I think it is the motor. Armature is supported on one end with a bearing (brush/commutator end) and other end has the splines that fit on the shaft on the cart. You can't really bench test because you would need specialized equipment. I can't advise you on motor repair. If it were me on a motor that old I would take it to a shop with capability to service it or just buy an new, better one. But that's because my interest in DIY repair is very limited. There are people here who have done some motor repair. Hopefully they will comment but if they don't you may want to start a new thread specifically for motor repair to get their attention.

07-13-2020, 03:24 PM	#16
kevinclark93 Not Yet Wild Join Date: Nov 2014 Posts: 9	Re: Marathon 36v Jerks repeatedly but does not go. I think it is the motor. I have not looked at he wheel splines. It is a possibility but I figured they would still spin the tire off the ground as opposed to jerking. I can also spin the tire and back drive the motor so it seems they are transmitting torque, but probably worth checking. There has to be a check to condemn the motor before I go buy a new one. I guess my next move is to take it apart and check the windings.
kevinclark93 Not Yet Wild Join Date: Nov 2014 Posts: 9

07-14-2020, 04:52 PM	#20
Bama Brad Gone Wild Join Date: Jul 2018 Location: Ramer, AL Posts: 1,450	Re: Marathon 36v Jerks repeatedly but does not go. I think it is the motor. OHH No! I hate it when he says that

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