86 CC won't move

[La Serna Regiment]

Our high school band has been using an '86 CC everyday for years. We use it to tow a 3,000± pound trailer with the pit instruments and a few band members to keep things from rattling around. Saturday at a field show it just quit. No odors, no burning, just relay clicks in forward or reverse.

It has a 36v resistor system. The batteries are a year old and show 39 volts. We did add a gallon of water to cover the plates. Most cells show a full charge with a hydrometer, but some will not float the last ball indicating a 75% charge.

All connections look good. No wires are burned. Each relay clicks on cue from the micro switches (square can with red ends). The F/R switch has clean contacts with no signs of burns or voltage loss.

The first relay (drivers side) energizes the bus bar at battery voltage in reverse (19V).

In forward, the 5th relay shows battery voltage (39V) opposite the bus bar.

The relays show 0.3 ohms or less when closed. The resistors are not much higher.

Jumping the resistors does not make the cart move.

The motor spins freely when the cart is pushed.

Can I get this thing going for our show on Saturday? Where should I look for the trouble?

 

[HotRodCarts]

Welcome to the forum.

Jack the cart up and put it on jackstands and jump the master solenoid. If the cart runs replace that solenoid. Just because the solenoids are clicking doesn't mean they're good.
Also check the connections at the motor and see if you're getting power there. If you're getting power to the motor and all the solenoids are good it could be the motor. I believe the test procedure for the series motors is posted in the resouce section here. If not just ask.

 

[La Serna Regiment]

The stud melted off the windings to the field coil. The problem is identified.