Started to reverse, than QUIT everything

GCManiac

Hey folks,
Ran into a problem last night when leaving a friend's house. My 92 Marathon stared to reverse, then simply stopped. Voltmeter (aftermarket addition) still on and showed 38.6 volts. Cart would not move either forward or back. Key switch did turn on/off....based on voltmeter coming on/off. Pushed it into his garage
Found a comment by member JohnnieB in a thread that was great starting point for me....."Electrically, the drive system is basically three series circuits: high current, solenoid activation and throttle. So troubleshooting is straightforward, the symptoms alone often point to which of the three has a problem and then it is just a matter to troubleshooting a long piece of wire with a few lumps in it. "
Hoping the repair will be something simple (and inexpensive) , but after reading some info on Troubleshooting EZGO....I'm worried! Seems further guidance in troubleshooting and repairing will certainly be needed....and MOST appreciated. Given it started to move then suddenly stopped...what would YOU be looking at first?
Thanks for any and all help!

BGW

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GCManiac

I do hear a click in solenoid when lever turned to forward or reverse when key is on......

JohnnieB

If solenoid is energizing without pedal being pushed, the solenoid activation circuit isn't wired correctly, but that won't keep cart from running. It is just a safety issue that ought to be corrected after the cart is running.

Since the solenoid does click, measure the voltage between the controller's B- and M- terminals after the solenoid is energized and before the pedal is pressed. You ought to measure full battery pack voltage (38.6V?)

If not, use the attached schematic with the high current circuit highlighted to trace the long piece of wire with lumps in it. Lumps are F/R switch contacts, solenoid contacts, motor brushes, motor windings and MOSFETs in controller.

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Attachment-2 is a schematic with solenoid activation circuit highlighted, so you can get that working right after you find/fix the high current circuit problem. It could be wire correctly and have a bad MS-3, or MS-3 not adjusted properly. MS-3 contacts ought to be open when pedal is up.

Attached Images

	Pot Box cart with high current circuit traced.JPG (124.9 KB, 0 views)
	Pot Box cart with KSI traced.JPG (121.2 KB, 0 views)

GCManiac

Hey JohnnieB.....thanks for the help!
In fact, when solenoid just clicks, and pedal not further depressed, there is voltage across M- and B- (although one volt less than pack)
Guess I'm not clear from your reply whether that's good.....and what I should be checking from here.
I have checked throttle signal and was a bit over range....but did seem to act right when pedal depressed.
When I checked controller input, it was approximately 0 (11mv) B- to B+
When checked output, it started at pack voltage when solenoid clicks, but did NOT go to zero as pedal depressed.

BTW.....solenoid wired correctly, it is an issue with pedal not always clicking micro switch on potentiometer when released.

JohnnieB

1. Should be same as pack voltage. However the 1V drop could be excessive resistance in the cables, contacts or connections.

2. The throttle checks I posted in the other thread are not for your cart, they were for a series drive with ITS type throttle, you have a 0-5k type throttle.

Disconnect the black and white wire from controller and measure between wires with an Ohmmeter. Should be less than 300Ω with pedal up and no more than about 6,000Ω with pedal down.

3. The is a problem here. You ought to get pack voltage between the controller's B- and B+ terminals when the solenoid is energized and about 3V to 5V less than pack voltage when solenoid is not energized (if there is a resistor connected between the solenoid's large terminals)

Check the cable from the battery pack's main negative terminal to the controller's B- terminal. A bad, but not completely open, B- cable might produce the symptoms your cart has.


4. Weak pedal return spring or gummed up pedal hinge. Or something along those lines.

Mooncarter

Jack up the rear end.

It may take off while you are tinkering with it.

GCManiac

JohnnieB ....sorry, seems I wasn't clear. I did check resistance between the two signal wires and found it to be less than 200 ohms and about 7000 ohms on full pedal range. A bit more than the 6K .....but presumably in the ballpark. (?)
I'll check the cable from main battery- to controller B- tomorrow. You think a sketchy cable would result in a rapid shutdown?
Hmmm....the readings I was taking on B+ to B- were done with resistor off.....both at solenoid and at controller. Will check in AM after connecting resistor at solenoid.
Thanks again for the help. Definitely appreciated.

JohnnieB

The resistance might be too high with the pedal down. The is an open potentiometer safety shutdown that triggers at about 7K, but the trigger point may have drifted quite a bit in the past 26 years the controller has been in use.

Try moving pedal up and down through its full range of travel several times. If there is some gunk under the wiper, that might clean it. However, that will only shut down the controller when triggered, so it ought to run at half pedal, or in reverse.

You also might be running into a HPD (High Pedal Disable) shutdown. If the pedal switch contacts don't open when pedal is up, the cart won't run.

GCManiac

Ok....trying to sort things out this SM...but more confused. ��
Key on, forward, solenoid resistor connected, controller varistor not connected, pack V 38.5
With solenoid not engaged, probes on controller B+and B- gives 30.2 V
With solenoid energized (audible click) with minimal pedal movement gives 38.5 V
Probes on M- and B- gives same results.
Should note that one leg of varistor just came in two when touched. ��
Inspection shows much corrosion. Guess I'll be buying a new varistor before going any further ��
Any way to sort the HPD issue? Pedal does seem to energize/deenergize solenoid.

JohnnieB

B- to B+ voltages look okay. Voltage down to 30.2 when solenoid contacts are open is a bit higher than I said, but the specs I gave were for a Curtis 1206 controller used in later versions of the EZGO series drives, rather than the Curtis 1204 or 1205 your cart has. Also, the pre-charge resistor might be something other than the 250Ω used with the 12065 at 36V. In addition, the 26 year old filter capacitors might be leaking more now than they did when they were new. Bottom line is the voltage drop is higher than expected, but probably okay.

The varistor is not needed for operation. It is a surge protector and I'm not sure why the EZGO design engineers put one between the controller's B- and B+ terminals. Further troubleshooting without it will do no harm.

Attached is the manual for a Curtis 1204/5 controller. The HPD feature is optional, but I'm pretty sure the controller used by EZGO had that feature.

The fact you have about 300Ω with pedal up may be triggering it. See Page-26. Also take a look at the Ohm reading chart on Page-29 and the throttle input voltage chart on Page-30.

Attached Files

Curtis Controller 1204_05 manual.pdf (415.2 KB, 0 views)