1995 (?) EZ Go Golf Cart Troubleshooting

[KPRCBD]

Hi,

I am new here, so apologies if I misstep.

I could really use some help in troubleshooting my EZ-Go golf cart. I am not 100% certain of the year but based on the parts it appears it is between 1995 and 1997.

The cart was working great then one day it stopped working. A few times we were able to get it to run in reverse but not consistently.

I started taking voltage readings and based on some informaiton I found on this forum, it seemed that it was the controller (zero volts between M terminal and the B+ terminal, with no change in voltage by pushing the gas pedal). I purchased a new OEM controller and it still doesn't work and I am getting the same voltage readings. (zero volts between M terminal and the B+ terminal, with no change in voltage by pushing the gas pedal). Because I had the other parts on hand, I then replaced the solenoid (as well as the diode and resistor) and the directional switch. Nothing. Batteries are brand new and fully charged.

I next started taking continuity checks and there doesn't seem to be a break in any of the lines. The pedal switch (under the floor mat) works when I test with continuity but I notice there is no voltage there or coming into or from the speed adjuster coil. There is also no voltage on any of the small terminals of the solenoid. Furthermore voltage difference across solenoid large terminals is only 1 volt, and I saw some posts says it should be 3 (but I see this on both the old and new solenoid with the old and new resistor). Key is on, and when I trace the wires from the pedal switch it goes back to the pin connector of the controller.

The one thing to note is that when I put in reverse, the buzzer sounds. It really struggles when the pin connector is connected to the controller, but really loud when I disconnect the pin connector from the controller. Also when I push the pedal, the buzzer stops.

Don't really know where to go from here. Does anyone have a wiring diagram with expected voltages? Any help and suggestions would be appreciated. I'm thinking something may be mis-wired (before I started troubleshooting, one of the employees was messing with it, so I'm not 100% certain of whether things were moved).

[Sideways]

KPRCBD - You will need to let these guys know which drive type your cart is (Series or Sepex) most can tell by where the F&R (Forward & Reverse) is mounted.
What is the pack voltage, 12hrs after a full charge cycle completed? (without using the cart) Also check voltage of each battery individually. See Johnnieb's state of charge chart below.
Lots of great people here that can help.

[KPRCBD]

Thanks for posting, and apologies for the delay in responding. I had to take apart the cart more to get information on the motor. I have no idea how to tell if it is series or sepex. It has 4 terminals (A1/A2, S1/S2).

The electrical parts of the FWD/REV switch is mounted in front of the controller (passenger side), and operated by a linkage connected to the FWD/REV lever which resides between the passenger and driver.

As for battery voltages, the voltage across the 3 battery bank is 38.4V (disconnected from charger), and each individual battery is 12.8V when disconnected from one another.

On the battery side of the solenoid, I see the 38.4V. On the other side of the solenoid I see 37.7V. No voltage on the Red or Black terminals on the solenoid.

On the controller I see 37.7V on the B+ and M- terminals. I see 0V on the B- terminal.

I also see 37.7V on all 4 posts on the back of the direction switch

Any idea what voltages I am supposed to have at the A1/A2, S1/S2 terminals of the motor? It looks like left, top, and right posts on back of direction switch (directions based on looking at posts) connect to motor S2, A2, S1 respectively, with M- of controller connected to motor A1. Any idea if any of A1/A2, S1/S2 should have continuity to each other?

Thanks in advance for any help.

[JohnnieB]

Sounds like you have a series drive cart.

Does the solenoid click when pedal is pushed?

If not, the problem is in the solenoid activation circuit highlighted in red on attache schematic. (The schematic is for a newer series drive, but the only difference will be where the wire from MS-2 connects to battery voltage)

[KPRCBD]

Thanks for the drawing and advice. Currently the solenoid does not click.

In looking at the drawing, it lines up with the schematic that I drew from doing a hand over hand. For mine, on MS2, the Blue from the key switch is connected to the FWD MS2 switch, and the red wire from MS2 connects to a white wire going into the charger receptacle like the drawing you provided, but there is no connection post for A2 on the controller, so post C does not connect to A2 on the controller.

I did not know there was a switch in the charger receptacle. Makes sense though, so you cant drive off plugged into the charger.

I will put the batteries back in tomorrow and check the voltages on the solenoid activation circuit.

Any way to know the orientation on the ABCD posts? It appears that A and C are connected the same, but looks like B and D are opposite from my drawing. May just be perspective? It is correct if I line up the drawing facing the front of the posts (standing in front of the cart looking toward the rear), but it is incorrect if I line up the drawing facing the rear of the posts (standing behind the cart looking toward the front, and where the actual cables connect). Figure to check everything since someone else had their dick-skinners in there before I started troubleshooting.

I'm only curious on the posts because I notice that S1, A1 and A2 all have continuity with each other in the FWD position. The ABCD post in FWD position seems to put A2 and S1 in continuity through that. Should A1 and A2 have continuity (I don't think you would otherwise no potential for EM)?

What voltage should M- have on the controller? It seems to always have battery voltage whether in FWD or REV, and that is connected to A1

[JohnnieB]

Here is a schematic, without an A2 terminal on controller, with the high amp circuit highlighted. F/R is in F.

The terminals on the F/R are A at bottom and C at the top. B and D are at 3 and 9 o'clock and the stator windings are between them. If the direction of travel doesn't match the direction selector lever then swap the cables on B and D. There are more than one way of wiring the F/R that works.

With no cables connected to Motor:
A1 -> A2 should measure between 0.2Ω and 2.0Ω
S1 -> S2 should measure between 0.8Ω and 3.0Ω
A1 -> S1 should measure OPEN
S1 -> Motor Case should measure 5,000,000Ω or more.

Measuring between the controller's B- terminal to the M- terminal, you should get FULL battery pack voltage when the pedal is pushed just far enough to make solenoid click and the voltage ought to smoothly decrease to about 0V as pedal is slowly pushed to floor.

The voltage you are reading with pedal up is coming through the precharge resistor between the solenoid's large terminals.

The purpose of the precharge resistor is to keep the filter capacitors inside the controller charged to reduce arcing of the solenoid's contacts and prolong their life. The voltage measured at M- (or B+) will be slightly less than battery pack voltage due to the filter capacitors being constantly discharged for safety reasons.

[KPRCBD]

@JohnnieB thanks again for the schematic. It turns out that the problem was indeed the charger receptacle interlock. I bypassed the reed switch and problem solved. I have ordered a replacement. Thanks for all your help.

I did check the motor continuity before I put the batteries back in. I only saw the A1, A2, S2 continuity through the F/R switch. When disconnected the wires the resistance of the motor posts was about what you provided.

[JohnnieB]

Originally Posted by KPRCBD

@JohnnieB thanks again for the schematic. It turns out that the problem was indeed the charger receptacle interlock. I bypassed the reed switch and problem solved. I have ordered a replacement. Thanks for all your help.

I did check the motor continuity before I put the batteries back in. I only saw the A1, A2, S2 continuity through the F/R switch. When disconnected the wires the resistance of the motor posts was about what you provided.

The reed switch is a high failure item and has a nasty habit of misbehaving when you are out in the middle of nowhere, so most of us just bypass it and loop the charger cable through the steering wheel if driving off with charger plugged in is and issue.

EZGO stopped installing reed switches sometime in 2007 or so. My 2008 has a factory installed mini pigtail fuse instead of a reed switch. The triangular 48V port used in RXV and TXT48 carts have an electronic version of the reed switch that is almost as troublesome and the entire charger port has to be replaced to fix it. So it is often bypassed as well.

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The actual Ohmic values for the motor are in Milli-Ohms, but it takes specialized test equipment to accurately measure values below about 10Ω or above about 1MΩ, so the values listed were what is typically measured by a typical Digital Multi Meter, so anything close is good enough.