98 TXT Motor pulses but won't run

[JGD1998EZGOTXT]

This is a 1998 TXT Series 36V. When I start to press the accelerator, the motor will pulse like it wants to run but no matter how far I push the accelerator pedal down that's all it does. It did this once 8 months ago but started to run as I worked the pedal back and forth. Based on that (and I did measure the batteries this time) I don't believe it's the batteries.
I get 36V at the B+ on the controller.
I hear the solenoid kick in as a push the pedal down.
I disconnected the batteries and the 6 pin connector on the controllerand tried to measure resistance at the black and white wires on the 6 pin (only 4 used) connector on the controller thinking I would see a resistance change from the accelerator pedal. It was 10+ ohms but only changed slightly thru the pedal travel and actually looked like it was floating. I looked inside the pedal box and saw that it is an ITS, so I'm not sure what I should have seen when I tried to measure ohms but expected this to change the speed. Not sure how it can when I don't see any real change.
What is the most likely problem with the motor only pulsing and not running and where should I begin? Thanks for any help.

[yamahaguy97]

As you said it could be the round "doughnut" speed sensor under the floor. I was also thinking your motor brushes or armature. Might be worth examining

[JGD1998EZGOTXT]

After some additional time to think about an inductor, the basic function, and how that might work as an accelerator pedal input to the controller I came to this.... An oversimplified explanation is that an inductor has a magnetic field, the metal rod on the pedal when inserted inside the inductor, disrupts the magnetic field. The controller is hooked to it and senses the changes that come back to it from the disrupted magnetic field and adjusts power to the motor. Also, after some more searching (not sure why I didn't find it initially) I found a thread with quite a discussion about the ITS, it's function, and what's inside it. The thread is called, Inductive Throttle Sensor. Someone on the thread dissected an ITS and found there's a small circuit board inside so it's not just a simple inductor, it has some other functions and is powered by the controller thru the blk/wht wire pair. Since it's not a traditional resistance like a potentiometer that I guess was used previously, the circuit diagram shows kind of a hybrid symbol (not an inductor and not a resistor) and it also means you can't make a simple resistance measurement like I tried. Someone on that thread put a scope on the ITS and it revealed pulses which I believe is what I'm feeling when I try to make it go. Clearly I have a problem and perhaps it's either that the ITS is pulsing the controller and shouldn't or the controller is getting pulses that it should get and isn't dealing with them properly and thus is pulsing the motor instead of just ramping the voltage up/down smoothly. I found some additional tests that I will try soon and hope to narrow this down or find the issue. I hope it's the ITS because it's cheaper than a controller.

[JohnnieB]

The ITS (throttle) signal not telling the controller to pass more amps to the motor could be the problem, but could some other things also.

To check the ITS signal, connect your DVM's negative test lead to the B- terminal on the controller and the positive test lead to Pin-1 (white wire) of the 6 pin plug. Go into the backside of the plug when it is plugged into controller.

When the pedal is pushed just far enough to make the solenoid click, you should read 0.4V to 0.6V. When pedal is on floor you should read 1.5V to 1.7V.

Moisture in the pedal box will cause ITS issues and moisture/corrosion in the inline connector between the cable from the pedal box to the cart's wiring harness will also cause ITS issues.

-------------
The ITS sensor in the pedal box is an electronic device whose current throughput is varied by iron slug being inserted into it. The voltage output of your Ohmmeter probably isn't high enough to turn on the electronics, so it cannot be checked that way.

Attached is a schematic of the ITS sensor and a block diagram. The 10Ω you read is the forward biased resistance of two of the four diodes in the input bridge. Not sure why the Ohmic value varied when the pedal was pushed.

[JohnnieB]

Looks like your latest post was posted while I was typing.

Yep, the ITS sensor is far more than meets the eye and it is only 1/3 of the ITS circuit. The other 2/3 are inside the controller, power source and detector, so the correct test voltages depend on which make/model controller it is attached to.

The voltages and test points I posted are for a Curtis 1206 controller, also apply to a Curtis 1206SX (DCS), but not to a Curtis 1206MX (PDS) or Alltrax aftermarket controllers.

-----------
I tried to come up with a test for a standalone ITS sensor, but the iron slug moved by the pedal is part of the equation, so the best I could do is make an ammeter fluctuate when I inserted a metal rod into it. Basically, I can tell if it is dead or alive, but not if it is working properly.

[JGD1998EZGOTXT]

I did the suggested test......
When the pedal is pushed just far enough to make the solenoid click, you should read 0.4V to 0.6V. When pedal is on floor you should read 1.5V to 1.7V.

....and I got .504 volts and 1.64 volts so it appears to be OK.

I found some additional checkout for the controller in another thread.
One was a controller output test, with the rear wheels off the ground, neg DVM probe on M- and pos DVM probe on B+. Initial reading was near zero (.3Mv) which was OK. When depressing the pedal the voltage would increase (along with tire speed) but it would begin to decrease and not consistently. Once it got to 7 volts, then started to decrease. Another time or two it made it to 20V then began to decrease. Removing the orange wire from the F-R microswitch did NOT give at or near battery voltage. The result was-----replace the controller. There was another controller test that also gave results that indicated the controller needed to be replaced. Ouch.....
I'm looking at a service to take my core, rebuild and return it unless the consensus is that it's a bad idea.

[JohnnieB]

All of the components in your 18+ year old controller are the same age and the first few of them have failed. Only the failed components will be replaced by the re-builder, so you'll end up with a controller that is on the brink of the next failure. In other words, a ticking time bomb.

[Volt_Ampere]

Rebuilding controllers is not a very good idea. Buy an aftermarket one like Alltrax.

[BobBoyce]

Originally Posted by JohnnieB

All of the components in your 18+ year old controller are the same age and the first few of them have failed. Only the failed components will be replaced by the re-builder, so you'll end up with a controller that is on the brink of the next failure. In other words, a ticking time bomb.

Well said JohnnieB.

Prior to me getting involved with golf cart controllers, I was heavilly involved with working on and working with Curtis controllers for larger electric vehicles and heavy equipment. Those controllers are more expensive for a reason. There is a lot more at stake for a vehicle that is used in traffic on highways, or is used on powerful equipment that can do a lot of damage if a malfunction occurs. The quality of the controller electronics is higher. More thought is put into the operating system (software) and VCL (vehicle control language) in those controllers.

Golf cart controllers tend to use microcontroller chips in place of full microprocessors, and lower quality components, in order to save on build cost. The golf cart market just cannot justify high cost/high quality controllers be installed by the factory.

So expect failures to occur. I suggest that everyone buys a new controller instead of having a controller rebuilt or repaired. I have the facilities to repair and rebuild Curtis controllers, and I would not even do it on a controller that I own. The only type of work I will do is to reprogram a controller with corrupted memory or software/VCL, as long as every bit of hardware within that controller tests 100% good. Controllers that have failed hardware are good for doing software testing, on the bench, but I would not attempt to repair one for use in a vehicle.

Bob

[rib33024]

In your first post you say the batteries are good. 36 volts is only 45% charged. What volts is the pack dropping to when you try to drive the cart? how old are the batteries