Previously converted 1988 EZGO Marathon stopped running

[blue00018]

I have a 1988 EZGO Marathon that I have owned for about two years. Recently it stopped running. This is my first golf cart and I have little prior knowledge about golf carts.

I started to research my problem on various internet sites, obtained and reviewed the 1988 Marathon parts manual and eventually discovered that my cart was not the same as the diagrams for a 1988 Marathon. I obtained enough knowledge to realize that it has been converted from a resister coil to a solid state controller system. The change has made it difficult for me to diagnose my problem as it is now wired completely differently from diagrams that apply to either system (I have studied the Curtis 1204 manual in analyzing the wiring to my controller as no info was available for the controller in my cart).

As converted it is a 36 volt system with a 974-3615-610 36 volt Trombetta solenoid, Hyundi GOC-100 275 volt controller, a manual F/R switch, a PB-6 type 2 wire throttle and I believe it has the original motor. Many original wires in the cart have been taped off. On the controller the black and white throttle inputs are present but the other end of wires are not connected to anything. Direction change is accomplished by a wire from the F/R switch that connects to the throttle and then goes to the 2nd small lug on the solenoid with a wire from that lug to the KSI input on the controller.

Until recently the cart operated well, maintained speeds and changed directions without incident. It now no longer runs. I did test the motor, disconnected from the system and it ran. There is full voltage in the batteries (37.2 Volts) and almost no reduction when the pedal is engaged. When performing varied tests I register voltage increases when the pedal is engaged so I believe the throttle set up is not the problem.

I have attempted to test the solenoid. It clicks when the throttle is depressed, there is full power at the first large lug, no voltage at the 2nd large lug until the pedal is depressed it then rises to the 37.2 volts and back to 0 when the pedal is released. With throttle engaged there is full power at the 2 small lugs and also at the KSI input on the controller. There is no resister between the 2 small lugs of the solenoid but I saw some older marathon diagrams where there is no resister on the solenoid so I cannot tell if mine should have the resister or not. From some of my reading the solenoid may be faulty as the voltage at the 2nd large lug is the same as the system but this may be because there is not resister between the two small lugs and I cannot tell if mine should have the resister or not and whether the test show a solenoid failure or not.

I have tested the controller using the tests in the Curtis 1204 manual. From B+ at battery to B- on the controller there is no reading with until pedal is depressed then it goes up to 37.1. Testing controller B+ to B- no power until pedal is depressed then goes up to 36.9. KSI has no power till pedal is depressed then goes up to 36.8. B+ to M- is zero till pedal depressed then goes up to 36.9 and same with A2 pos lead connected to neg battery terminal. I cannot understand why, if power is exiting the controller, the motor does not start. In summary, I am confused and stuck and would very much appreciate your guidance before I start blindly buying replacement parts.

Thanks

Bob Parsons

[DubK]

Sounds like maybe a bad f&r switch or possibly controller if solenoid is still clicking. I cant tell you for sure as I'm no expert. But it sounds similar to a problem I once had and I changed the f&r out and it worked. Follow a diagram for a solid state Marathon (89-94) or a Medalist diagram. Should be closer to your set up. Can I see a picture of your throttle set up? Specifically what was used to link the pedal to the throttle..a rod or a cable of some sort? I'm converting a resistor cart to solid state and looking for an easy throttle option.

[JohnnieB]

I the controller you are using is supposed to be a 1206 replacement or clone, then the speed control "Valve" is between the B- and M- terminals, so getting a seemingly normal voltage between M- and B+ doesn't mean all that much for troubleshooting purposes since an intact circuit and a circuit with undesired opens in it, can give the same results.

Measure the voltage between the controller's B- and M- terminals. When pedal is pushed just far enough to make solenoid click, you should read full battery pack voltage. If you don't get it, there is an open someplace in the high amp circuit, the F/R switch being the prime suspect.

If you do get pack voltage when solenoid first flicks, slowly press pedal to floor and the voltage ought to decrease to about 0V.


If it doesn't, the throttle input may be bad, the controller may be bad, or the controller might not be powering up for some reason.

------------
FWIW: If the high amp circuit is intact, the speed control valve (MOSFETs) is to only open in a series loop, so all the voltage applied to the loop is dropped across it, and it becomes a short at full throttle, so no voltage are dropped across it.