2009 Carryall 2 acceleration dropping in and out

[electricservice]

TL;DR: Accel drops to super low speed intermittently. Cycling pedal takes a very long time before speed picks up, sometimes does not help at all. I have replaced the batteries, converted to MCOR 4, completely bypassed the OBC, installed Delta Q charger.

Initial fault was power cutting in and out, seemingly random. Vehicle accelerated, dropped to low speed, pumped accelerator to no avail. Eventually power would come back. Installed new batteries, no change. At this point, it would no longer reach high speeds, could feel the high torque for an instant when throttle was initially floored, but went no faster than walking speed.

Passed MCOR pot sweep test and switch function test. Removed MCOR because I doubted my tests, couldn't fit DMM leads onto pins, attempted to open MCOR, swiftly gave up, reinstalled, found the switch no longer functioned. Converted to MCOR 4. Installed Delta Q charger (IQ charger was going out), spliced white and blue OBC wires, vehicle seemed to drive normally. Delta Q is operating correctly.

One day later, almost exclusively slow walking speed. Upon resetting OBC, speed picked up. Completely bypassed OBC leaving white and blue wires connected. I understand that having a lag between letting off the accelerator and when it speeds up is normal (?). But now it will intermittently drop to low speed with the accel still depressed.

I do not have the proprietary diag tool, and I don't want to purchase one, as this is not my vehicle, and I do not service club cars often. In my eyes, it is likely the controller, perhaps overheating, though it never gets excessively hot even immediately after the fault occurred. Wiggle tests with wiring produced no results. Any insight on how to test the controller? Thanks for suffering through.

[mgray70]

Sounds like the speed sensor. Is it a regen cart? Try pushing the cart and see if you get the roll away braking and the beeps. If not the speed sensor may be bad.

[electricservice]

Speed sensor is working. Pushing vehicle engages buzzer and electric brake. Unplugging speed sensor while driving leads to constant low speed operation.

[mgray70]

Maybe thermal protection in the controller. I was just trying to rule out all the cheaper, easier items. Maybe someone with a little more knowledge than me will stop by and help out.

[electricservice]

Still working on it, but I found that stepping on the brake with the accel depressed sometimes speeds the wheels up. So to test, I manually tightened the shoes, and it causes the wheels to speed up. It isn't perfect, and sometimes drops back to the slow speed. Right now I'm trying to find the sweet spot where they run at full speed all the time. If anyone could explain this, I'd be very appreciative.

Edit: FWIW the shoes have plenty of life left on them.

[TahoeDawgZ71]

What's the vehicle serial number?

[electricservice]

QB0926-030450

Is there some sort of load sensing going on?

[TahoeDawgZ71]

Originally Posted by electricservice

QB0926-030450

Is there some sort of load sensing going on?

This is an IQ Plus system with 8 batteries and a big AMD/ADC motor with a top hat style speed sensor right? Description for that serial number prefix only tells me "HD IQ CA2"

I'm trying to figure out if it's the IQ plus system or the AC Drive system.

[electricservice]

It's the IQ plus. Further testing is pointing me toward an intermittent encoder fault. More diagnosis to be done soon.

[TahoeDawgZ71]

A bad walk-away relay can cause this problem. It's the 48 volt relay mounted right next to the solenoid. A bad circuit breaker next to the tow/run switch can also cause it. You'd need a Curtis handheld scanner to point you in the right direction. The IQ Plus system is MUCH more complex than the standard golf car IQ system.