Mysterious Loss of Power

[Mako]

I have a EZGO 36 volt Series car with a upgraded 8hp motor and controller! The car will run and then loose all power. You can wait and it might start again or not. When it looses power it appears that the load voltage is lost. I have check all connections by disconnecting from batteries and cleaning with wire brush. Once I clean then I re install and tighten. My load voltage is approx. 39 volts and each battery is approx. 6.2 volts. I have 37 to 39 volts across the resistor at the top of solenoid. I also have 37-39 volts on 2 wires from controller to motor. What should the voltage be from the controller? Is there a wiring diagram with suggested voltages that I can print? What could be causing this loss of power and why does it come and go with no rhyme or reason?

[scottyb]

Just for fun - connect the meter to the pack and drive ( alligator clips or ?) Give us the lowest reading you see.
If you have a hill handy - test going uphill, even better.

[Mako]

Once it starts running again I will test the voltage under load.

Thanks

[Mako]

As of now it will not run. Voltage is 38 volts is across the resistor on the solenoid and have the same type voltage on cables going to motor on top of controller. What voltage should be at these locations?