1990 Marathon No Go After Upgrades

[JohnnieB]

Originally Posted by DubK

1. In the first photo is the voltmeter. There is no knob position on it.

2. The second photo shows the DVM attached to the battery + and solenoid + making the open beep sound.

3. Third photo I am holding the cable attaching the solenoid to the controller B+.

4. Fourth photo is my motor and the studs. Yeah it's old looking. 29 years old.

5. Fifth photo is the wiring diagram I used because it matches my motor stud pattern. I double and triple checked it.

1. I found an instruction manual for your Klein Tools ET250 and it only resolves voltage measurements down to 1V. To troubleshot an electric golf cart a resolution of 1/100V is needed for checking individual battery voltages and 1/10V is usually adequate for battery pack voltages.

2. The beep and the audible continuity symbol on the display indicates there is <270KΩ of resistance between the test lead tips. The symbol for an open is "000" on the display.

3. Good, I couldn't see it in the 207x276 pixel photo.

4. & 5. The only difference I see in the stud locations on your motor and drawing is the motor installed on cart is rotated about 90° CCW. Studs in motor picture from top to bottom are A1 - S2 - A2 - S1. Please note the "A" studs are mounted on the end cap while the "S" studs have cutouts in the end cap and will stay with motor case when end cap is removed. (Armature brushes are in end cap while Stator windings are in motor case.)

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Unless otherwise stipulated, all voltage measurements are referenced to the battery pack's main negative terminal.

The voltage between the battery pack's main negative terminal and main positive terminal should be 38.2V when fully charger. Individual battery voltages should be 6.3.7V and there should be no more than 0.1V between the highest and lowest battery voltage.

[DubK]

Again, thank you for the great information. I learn so much on here everyday! Sounds like I bought the wrong volt meter then. I got one of the cheapest ones home Depot had. But I will get to messing with it again tomorrow night and check on those A and S posts on the motor to see if I wired it correctly. I wired it like the diagram said which would be backwards according to the info you gave me. I didn't know the A and S terminals looked different so that's a big help. I got frustrated with it today and called it a night early! I'll report back soon. Thanks again.

[JohnnieB]

The way the "A" studs are mounted is different than the way the "S" studs are mounted and as long as the two cable that ought to be landed on the "A" studs are landed on the two "A" studs and the two cable that ought to be landed on the "S" studs are landed on the two "S" studs, the motor will run, if the other stuff is wired correctly.

The direction the cart travels might not match the direction selected by the F/R lever, but it'll run and getting cart direction and F/R lever to match is simply a matter of swapping a couple cables.

[DubK]

Makes sense. I have a brand new charged battery pack. It reads 38.2 from the main + to main -. So I tried the DVM on the controller M- and B- once more. It is only reading 8 volts and when I slowly press the pedal it goes down to 0. I l know I read it should be 38.2. but only reads 8 volts. On other connections I am reading 38.2 volts. What would this mean?

[JohnnieB]

Not getting full battery pack voltage between B- and M- means there is a bad connection, contact or cable somewhere in the high current circuit highlighted on the schematic I attached to post#15.

Looks like you've new cables and a new solenoid, so I'd start by measuring the voltage on the four studs on the backside of the F/R switch assembly. With pedal pushed just far enough to make solenoid click, they should all read 38.2V.

[DubK]

Originally Posted by JohnnieB

......I'd start by measuring the voltage on the four studs on the backside of the F/R switch assembly. With pedal pushed just far enough to make solenoid click, they should all read 38.2V.

All to the main - I'm assuming?

[JohnnieB]

Originally Posted by JohnnieB

Unless otherwise stipulated, all voltage measurements are referenced to the battery pack's main negative terminal.

As stated in earlier post in this thread.

In other words, unless specifically stated otherwise, the negative test lead is always connected to the battery pack's main negative terminal.

That way everybody is on same page and all voltages are positive going.

[DubK]

Originally Posted by JohnnieB

Looks like you've new cables and a new solenoid, so I'd start by measuring the voltage on the four studs on the backside of the F/R switch assembly. With pedal pushed just far enough to make solenoid click, they should all read 38.2V.

So my results from this test are as follows. Only the top terminal of FR switch assembly reads 38 volts (since my DVM rounds to the nearest volt). The rest of the FR switch terminals make the DVM beep and show the audible continuity symbol on the display indicating there is <270KΩ of resistance between the test lead tips. Not exactly sure what this means since this is all a foreign language to me. But do I need a different volt meter, a new FR switch? Which I plan to get an HD version anyways while upgrading slowly to 48V.

[JohnnieB]

The high current contacts of the F/R switch are not making good contact. Try shifting between F and R several times and they might, but you probably do need a new F/R switch assembly.

[DubK]

It works! Thanks to you JohnnyB for helping me narrow it down to a bad f+r switch. I ordered a new HD one from Scotty and installed it this morning and it fixed everything! Y'all don't know how happy this makes me. I've been stumped on this for so long I was starting to lose hope but thanks to the great people of this forum I can now enjoy my cart like it's meant to be!

So I put it to the test today. After the new 400amp solenoid, new 2gauge cables all around, new Duracells, and new HD F+R switch (all from Scottyb), this old 3 wheeler runs better than new. Even with the stock Curtis controller and stock motor it now does a steady 16mph all day long on flat ground. It rides so smooth! I might upgrade to a 500amp alltrax for more torque with passengers but for now it's perfect as is. The next step is paint/body work, and lights and more cosmetic stuff. Thank y'all again for all the help on this! I'm a very happy camper now.