[rmay635703]

There should be a regular Curtis 1209b inside there

If the motor is actually getting amperage you have blown brushes or something is seized, should make a humming noise while it tries to move

A simple ammeter off the last battery will show how much current is flowing
My guess is very little

These cars commonly have bad connections by the steering column along with bad grounding points on the chassis.

If you disconnect, validate and repin the 12 volt stuff in the cab and it still won’t go I would take the controller out of the car lift the front wheels up, chock and secure the chassis and connect the controller straight to the motor without any contactors then attach to the batteries directly, simulate a throttle with a resistor and see if there is life,
If not hook a 12 volt battery straight to the motor to see if there is life.

My guess is that the signal from the throttle isn’t making it to the controller, if not that the interlock is stuck due to bad wiring last possibility is a bad fr contactor

Process of elimination

Good Luck

 

[rmay635703]

If you don’t have an active voltmeter get one.

If you are cutting out you should see the voltage drop then pop up after the throttle kicks in and out.

The big black flooded agms in that car can have the center covers cut off you can then add a couple tablespoons of acid it each cell and trickle.

Do you have a 12 volt load battery tester and charger?

If you do you can see but you probably have a failed battery or two.

 

[rmay635703]

If you don’t have dash lights you probably need to solve that first

Is the 12 volt side of the car working?
Aka when on small 12v battery should be 13.5 volts.
Also when you turn on the car the brake vacuum pump should sputter to life, Putting it into F then stepping on the gas should make a solid metallic click.

If the 12 volt is too low or the dashing wiring is bad the car sets the interlock which cuts power to the motor

As for voltage drop you need to see the whole pack voltage if it drops a lot after turning on the car and pressing the gas you have bad batteries.

72 volts of lead acid are basically flat when you reach 72volts resting voltage
I am uncertain where the LVA is on your car but on mine it’s pretty low but I have a 48 volt miles.

 

[rmay635703]

I don’t have a load tester.
I have a good meter and a genius 7200 charger.

I will test the drop.
I did have it on one side of the contractor last night and the voltage didn’t change when hitting the pedal. Should I test voltage drop at the battery ?

Based on the above it Sounds like no current is flowing