EZGO Intermittent slow speed

[Philly]

Hi All,
Before I describe my fault I would like to mention that everything has been replaced on this 2002 EZGO TXT PDS buggy, i.e. Curtis controller, batteries, PDS inductor, speed sensor / magnet and main solenoid.
Machine runs great in forward and reverse but sometimes it will go at a walking pace with full pedal pressed. Sometimes if I stop and switch off / on with the ignition key normal speed will be restored. I checked the o/p from the batteries under the fault condition and they deliver a constant 35V while driving. I also checked the voltage across the motor terminals under the fault condition while driving and I get somewhere in the 27V region, so I can only deduce that the controller isn't delivering a full o/p intermittently. The Curtis controller has been changed twice with new units. Also under the fault condition the reverse speed seems to be faster than the forward speed. All leads and connections feel cold to the touch so no wattage losses due to bad connections etc.
Any suggestions before I go mad.

 

[Crash Test Dummy]

MAKE SURE YOUR BRAKES ARE NOT RUBING

 

[Philly]

Thanks for your reply.
I am willing to look at anything at this stage, however the fact that sometimes if I kill the power at the switch or go from Forward to reverse it may bring on the fault. Sometimes it will clear the fault and restore normal speed. The only thing I haven't changed is the paint color.
I had that problem some years ago with a new truck that would go slow intermittently. After being back to the dealer for the third time they discovered that the brakes were coming on when hot.

 

[Crash Test Dummy]

OK I WOULSTART WITH THE MOTOR TAKE IT OUT AND GET THE BRUSH STUFF OUT THEH LOOK AT BUUSEES




HERE ISCARBON BLOW OUT



WARNING
USE 2 WRINCHES ONE ON MOTER
ONE ON THE CABLE NUT

 

[Philly]

Since the motor is the only component I haven't changed I was thinking about it. That is why I measured the voltage being delivered to it's terminals when in the faulty condition. In the faulty ( running slow ) condition there is only 27V ( give or take ) at the motor so I ruled it out. When running normally and at full speed there is about 35V.

 

[Philly]

UPDATE,
Today I returned the the buggy and investigated one wire that was disconnected since my friend bought the machine. It's end was covered with insulation tape to avoid it shorting to anything, I suspect. I checked on the schematic diagram to see if this wire was original or an addon since the machine was worked on before I got to it. It seems that it is original, and connects pin 5 of J1 on the controller to the B+ on the solenoid. I connected it up and tested . Buggy ran up to full speed 100% of the time. I checked with the owner later this evening and he reported that all is running like new.
See the link for the schematic. The wire that was disconnected runs between the 250 ohm resistor and the beeper ( red wire ).
Fingers crossed. But is looking good so far.

https://i.pinimg.com/736x/99/bc/a4/99bca4c34d38bcefc1cb3f91a944feb2.jpg

Thanks to all.

 

[Snotty B]

 

[Crash Test Dummy]

as i read your drawing you eliminated the reed switch ??
if so it is ok BUT a warning should be given (to your friend ) the cart can be moved when plugged in
the reed switch cuts the power to the key when the cart is plugged in

 

[Philly]

Thanks for the diagram master cylinder.
It shows the wire from pin 5 to the B+ on the main contactor which was disconnected on the buggy. I wonder why it was causing slow speed intermittently. Unless one had the actual schematic of the controller it would be difficult to work out. Anyway, friend as reported the its running fine now.