2005 ezgo txt controller diagnostics?

[skullskidr]

Hey folks,
Need a little help here.
Factory 36v cart.
I was following the diagnostic sticky and got to the voltage between B+ and
M- on the controller. With key on and cart in F... I have 36.5v before the pedal is pressed when according to the diagnostics it should be 0.
Battery pack is 38.1
Cart background:
When the local church called me to look at it... s2 cable had burned/ corroded off of the f/r switch. I rebuilt the switch with a board and cam kit as it was toasty. Micro switches have continuity when they should.
What have I missed here? The cart should be running... but it does not.

[skullskidr]

Anyone? Anyone? Bueler? Bueler?

[kgsc]

I'm guessing series cart. Are you getting a solenoid click ?

[JohnnieB]

I suspect you are measuring between B- and M- rather than B+ and M-.

If so, that is a normal reading before the solenoid clicks, if there is a pre-charge resistor installed between the solenoid's large terminals.

[skullskidr]

Yes, a series cart. I get a solenoid click when the pedal is pressed
Key on, in F no pedal... B+ (post furthest to passengers side) M- (post closest to batteries) = 36.9V.
Same as above with pedal down = 37.9V
Key on, in F no pedal B- to M- = -1V
Pedal down = 0V

[JohnnieB]

Originally Posted by skullskidr

Yes, a series cart. I get a solenoid click when the pedal is pressed
Key on, in F no pedal... B+ (post furthest to passengers side) M- (post closest to batteries) = 36.9V.
Same as above with pedal down = 37.9V
Key on, in F no pedal B- to M- = -1V
Pedal down = 0V

The actual pedal up tests are Key=ON, F/R=F and pedal pressed just far enough to make solenoid click. That should give you 0V between M- and B+, or Full pack voltage between B- and M-.

You are getting the correct reading for pedal on floor for both, but the motor isn't spinning.

The only thing that comes to mind is bad MOSFETs or leaking filter capacitors in the controller.

I'd do a diode check on the controller. The attached drawing and .pdf file are for an Alltrax AXE controller, but the all work the same and the semiconductors used might have came from the same manufacturer.

Be aware there are filter capacitors between B- and B+, so be sure to discharge them or you meter might get zapped.

[skullskidr]

Thank you JohnnieB. I will give this a whirl first thing in the morning.

[skullskidr]

JohnnieB, I had a stroke of luck yesterday (maybe depending on how you look at it). A buddy of mine who just did a motor/solenoid/controller upgrade on his cart brought me his original, working controller and original solenoid he swapped a couple of months ago. I put them both in the cart and it did the same thing...solenoid click and no action from the motor. What should I check next?
Many thanks,
Kelley

[JohnnieB]

That more or less eliminates the controller and solenoid.

Let's start troubleshooting from square one.
The solenoid clicks, so the problem is in the high current circuit.

The attached schematic has the high current circuit for a series cart highlighted.

The high current circuit consists of 13 high current cables with connections at each end, four set of contacts in the F/R switch assemble, one set of contacts in the solenoid, The stator windings in the motor, the armature windings in the motor, the brushes and commutator in the motor and several MOSFETs connected in parallel located in the controller between the B- and M- terminals. (Also attached is a block diagram of a series controller showing the electrical location of the MOSFETs, It is for a Curtis 1204/5 controller, but they all work the same at block diagram level.)

Remove the pre-charge resistor that is connected between the two large terminals on the solenoid. This will make the controller side terminal read 0V when the solenoid's contacts are open and battery pack voltage (38.2V for fully charged battery pack) when solenoid contacts are closed.


Put the half ton cart on jack stands so it doesn't take off unexpectedly and run over something or someone.


Run a jumper wire from battery pack's main positive terminal (B+) to the solenoid's small terminal with two red wires on it. This will energize the solenoid and power up the controller without the pedal being pressed.

Place the F/R selector level in F. (As shown on schematic)

Measure the voltage between the B- and M- terminals on the controller.

If the high current circuit is intact, you will measure 38.2V because the MOSETs are not conducting and will be the only open in the series circuit.

If you get something other than FULL BATTERY PACK VOLTAGE, leave the black test lead of your DVM attached to the controller's B- terminal and use the red lead of your DVM to trace the cables, connectors and contacts in the high current circuit until you find the missing voltage.

[skullskidr]

Ok... I found the missing voltage. On the F/R switch I have pack voltage at A. After that...B, C & D...the wheels fall off of the bus... maybe .04v.
I did rebuild the switch with a new cam and board. Is there something I may have missed there?
Thanks again,
Kelley