2009 TXT no go

[Powder Burns]

OK I’m new here as a registered member, but I’ve lurked for months and the information here has been helpful several times. I appreciate the expertise that exists here, and the helpful community.

Now I have a problem that I need more specific help on. Here’s my situation:

Our cart is an EZ-GO TXT, 2009 model 36V
It has been lifted for off road use. We bought it in May 2020 to use on our land to give rides to our autistic son. (One of his favorite things to do in life is to be taken for golf cart rides on the trails through our woods, so we do this quite a bit.)

The cart has had some use, but is in OK shape overall. I’ve had to do a few small repairs so far. Once it rolled onto its side due to a slipping brake. Not too long after I righted it with my tractor and got the batteries all back in place and topped off, it started smelling that burnt electrical smell. Then it just stopped and I surmised that the solenoid overheated. I replaced it and all was good. This forum helped a lot for that repair.

I also had to replace the steering box after my wife ran it into a tree...

So while a total novice on electric golf carts, I’m fairly handy and have most of the tools I need.

My current problem is another electrical one. The cart just stopped running one day (first it ran, then we parked it to charge it, then the next time we tried - it did not run). I checked and didn’t find any obvious problem like before, but I figured that it might be another bad solenoid, as it seems that’s a weak area and the failure mechanism was similar to before. So I bought another solenoid an installed it - but there was no change.

I don’t get the solid solenoid click.

I’ve made these measurements and observations:
-all six batteries are Duracell, Nov or Dec 2017 builds (starting to weaken?)
-when charging, the battery bank is at 42.2V
-when I was testing today, the bank was at 37.8V
-batteries individually are 6.29V-6.31V, except one at 6.27V

On the solenoid, when I measure between the battery bank negative terminal and the larger terminals on the solenoid, I get 37.8V and 37.1V.
Measuring to the small control terminals gets about zero voltage. This is whether or not I’m hitting the accelerator pedal.

So I’m guessing that the solenoid may be OK, but I have some problem in the control circuitry.

Perhaps it’s a bad accelerator pedal switch?

What should I check next? What questions do the experts out there have for me?

[Powder Burns]

Any suggestions or help? My autistic son does not understand why we can't give him a ride, and I'm stuck at this point. Taking it somewhere for analysis will be difficult and expensive.

Thanks in advance.

[JohnnieB]

There batteries are all within 0.04V of each other, so that is a good indicator, and the are only about 3 years old, so they ought to have another year or two of usable life left in them.

The solenoid not clicking means the problem is in the solenoid activation circuit rather than the high amps circuit.

The first thing I'd check is the third (smaller) wire coming out of the backside of the charge receptacle. It should have battery pack voltage on it when the charger is not connected to the cart. That is the voltage source for the solenoid activation circuit and the reed switch in the charge receptacle is a high failure item.

The reed switch is typically bypassed since it always seem to fail when you are out in the middle of nowhere.

If it's not that, we need to know which drive system the cart has.
If the F/R selector is on the dash and there is a Run/Tow switch on the controller cover, it is a PDS.
If the F/R selector is a level by your knee, it is a series drive.

[Powder Burns]

Excellent suggestion - thanks!

I’ll check out that voltage tomorrow and report back.

FWIW the F/R selector is a lever by the knee, so it looks to be a series drive.

[Powder Burns]

OK, the small third wire from the charger receptacle DOES have battery bank voltage on it when the charger is unplugged. When the charger is plugged in, the third wire has the charging voltage on it. (Thus if I’m understanding its purpose, it sounds like it may have already been bypassed.)

What’s next?

[kgsc]

Try going through this diagram looking for where your voltage is dropping out.

[Powder Burns]

Yep I’ve been referencing that diagram.

I just pulled up the floor mat and checked on the pedal box micro switch. When the pedal is depressed, I get continuity through the switch, so it seems to be functioning.

BUT, I only get noise level voltage at either side of the micro switch, for both engaged and unengaged conditions. So now I’m going to get some voltages off the controller.

Sigh.

[Powder Burns]

Progress...maybe.

OK I found part of the problem. There is a four wire plug taking wires from the controller/solenoid to the pedal box switch. Red/Black/White/Green. The red one had a burned up connector. So I bypassed that one wire, plugged the other three back in, reconnected the battery bank, and carefully depressed the pedal.

I got an immediate sparking and smoke from the area of the top of the solenoid, so I let loose of the pedal and turned off the switch. That’s where it sits now.

Prior to this, I measured as follows:
Battery bank: 37.7V
M- : 37.0V
B- : 0V
B+ : 37.0V
I’m getting the 0.7V drop across the 250ohm resistor

Any ideas?

[JohnnieB]

Having 37V on B+ and M- indicates the throttle is wide open, or the speed "valve" in the controller is shorted

Eliminate the 4-wire in-line connector. Connect the individual wires with butt-splices or solder joints and waterproof connections with marine grade (adhesive filled) shrink tubing.

Might be getting some cross talk between the battery pack voltage on the wires to/from the pedal switch and the wire to/from the ITS sensor. (It is a fairly common problem, but usually it is the in-line connector getting wet rather than burnt.)

---------------
Pictures of the top of solenoid would help.

[Powder Burns]

OK I think I have the proper photo uploaded now.

IMG_4792.jpg

Also, there is some chance that a connection or two did get slightly wet in the past, as it's been real muddy here for a while. That might have contributed to the problem, but I can't be sure.