Trouble Shooting: '94 Medalist Speed Controller

Big Stace 99

I am working on my father-in-law's 1994 EZGO 36V Medalist golf cart. It has a 4" lift & 22" tires, but other wise stock (motor & controller). They don't work this cart hard, just putt around their farm a little.

The cart had quit working, so it got dropped off at my house (that's the son-in-laws job right?). I installed (6) new batteries and all new 8 guage cables. I slowly drove it out of the garage getting around a couple cars and it ran; however, when I pushed the accelerator pedal down, it quit & now won't move at all. I disconnected the motor, jumpered it and applied voltage, it ran fine. I then checked the small wires for corrosion & fixed one connector. The solenoid is clicking and I am getting voltage through it. I used my VOM to check the M to B- terminal and I was getting full voltage when the pedal was pressed enough to activate the solenoid; however, the voltage stayed a constant full voltage as I pressed the pedal all the way to the floor. I then checked the M to B+ and have no voltage there with the pedal pressed. So now, I think I either have: 1) a bad speed controller (likely) or 2) something it not telling the speed controller to work.?.? Is there anything on the Speed controller I can activate (energize) to see if the controller is for sure bad? The controller has a white plug in it with (4) small gauge wires (white/black/orange/red). I would just like to make sure it's the controller before I drop $500 on a new one ... ouch!

If it is the controller, are there any options for replacement or do I just have to bite the bullet & buy the EZGO part.

Thanks in advance for your replies & for helping newbie on the board!!!

BGW

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum

Sir Nuke

Frist off.....are you SURE you put 8 ga. cables on it?? seeing as how 6 ga. is stock cable size.


oh and btw.....Welcome to our happy little corner of the net, and to BGW. There is a BIG fridge on the back porch with anything you can think of in it...help yourself...of course only take what you can LEGALLY have. Make yourself at home on one of the big fluffy couches, kick your shoes off, put your feet up on one of the tables, yes we are allowed to do that, mom's, dad's, wive's, husband's, girlfriend's and boyfriend's here don't care....and take it easy.



oh...btw....every once in a while a food fight breaks out...so you may not want to wear nice clothes here.

Welcome!!

Big Stace 99

Just when you think you proof read your post well ... No, I didn't use 8ga, I used 4 gauge. Sorry!

Thanks for the welcome!

Sir Nuke

that's more like it......that's what guys usually upgrade to on stock carts.

Big Stace 99

I did consider using 12ga wire & let it double as a seat heater

And now back to the topic .... any ideas on troubleshooting my controller before I drop $500 on a new one?

Thanks!

Sir Nuke

hopefully either JohnnieB and or Scottyb will get in here.....either of them will know what you need to do.

Big Stace 99

Update:
Found a wiring schematic for the cart last night online. On the four small gauge wires in the molex type plug in the controller, I checked the red wire for voltage, it had full voltage when the solenoid opened. The orange wire shows continuity when the F/R switch is put in reverse. The black wire showed open when the accelerator pedal was appplied and the white wire showed variable resistance which varied with the movement of the pedal. I'm thinking that everything that should activate the controller is working, which I think has to mean my controller is smoked! Any other ideas to check would be appreciated.

As for controllers, do I have to go back with an EZGO controller, or can I upgrade to a better aftermarket controller even though my plans are to keep the stock motor?

Thanks Again!

Sir Nuke

no, you can go with an aftermarket.....but depending which size you get, you may have to get other things as well.

JohnnieB

Without an elaborate test bench, about the only way to find out if a controller is good or bad, is eliminate the other possibilities.

You've got new batteries, new 4Ga cables, the solenoid clicks and you get battery voltage between M- and B- when solenoid first clicks, but voltage doesn't decrease to near zero when pedal is pushed to floor.
That pretty much narrows it down to a bad controller or a bad throttle (ITS)

Connect your DVM's negative test lead to the battery pack's main negative terminal.
Check for B+ (battery pack voltage) at Pin-4 (Red wire) when pedal is pushed.
Pin-3 only has voltage on it when F/R is in R (It puts controller in 1/2 speed reverse mode)

The throttle input is pins 1 & 2
After solenoid clicks, the voltage on Pin-2 (Black wire) should be from 9.0V to 11.5V
When the solenoid first clicks, Pin-1 (white wire) should be 0.4V to 0.6V and when pedal is pushed to floor, it should be 1.5V to 1.7V.

If the controller is turned on (B+ on Pin-4) and the ITS voltages are correct, the controller is bad.

------------
Since you are running 22" tires, you will need a 400A or greater controller. (Stock controller is 275A, so a new stock controller will soon fail trying to turn the oversize tires)
Check out the Controller/Solenoid kits sold here:
http://www.cartsunlimited.net/Custom_Options.html

Big Stace 99

Thank You JohnnieB!

Excellent info! I will double check those tonight when I get home.

My guess is tomorrow I will be asking for advice on which controller to buy.

Thanks Again!