G8E good reverse, no forward

[kjewer1]

Hello. Great site! I've enjoyed the wealth of knowledge here in the archives for a while, but I'm running out of luck with this problem and could use some guidance. I've searched high and low regarding this issue, but I'm not sure what I'm seeing is the same thing others have reported.

This is a G8 electric 36v, kind of beat when I got it, but it worked for a little while. At one point I got a GPS speed in forward of 18 mph, which seems pretty good to me for this old beater. Reverse still works fine, with full power and speed control. It will spin the tires easily if I punch it in reverse. But forward has gradually gone to crap. Now it won't even move in forward at all, unless I get off it and ride it like a skate board. The motor squeals and sounds like it's trying to do something, but very little happens. Even with the wheels off the ground forward just has no power, the wheels barely turn. Here's what I know so far.

-I just disassembled F/R swich and cleaned it all up and reassembled. No change. It looked perfectly fine to me. Which was a relief, that ******* is expensive.
-The upper micro switch which seems to be for the reverse buzzer only had one lead hooked up (pink). Lots of posts in the search results say to unhook this, but that may onlyhelp in cases where forward speed is half of normal, not dead? Not sure.
-Disconnecting the reverse micro switch completely, no change as expected. Hooking both wires up, no change.
-There is a home made cable from the battery bank positive to the upper right connection on the F/R switch. As far as I can tell, that jumpers out the solenoid.

I can't see anything in the diagram that would affect only reverse. Everything seems to get used in both forward and reverse. All cables, controller, throttle pot, even all contacts in the F/R switch, etc. What am I missing here? Thanks in advance.

[cgtech]

F&R has four large wires. Disconnect 2 opposed large wires and temporarly swap them. If the f&r is somehow the problem, you will have forward and no reverse.

[kjewer1]

Thanks for the reply! I'll get a chance to test that on Wednesday. I'll report back with the results.

[kjewer1]

Ok, test results. I swapped two opposite wires on the F&R. It did reverse the operation of the switch, but there's no change in the behavior. Still struggles to move under its own power forward, goes like a bat out of hell in reverse.

Interestingly, what did seem to help was just running the motor in forward with the tires off the ground. After a short time of arsing aobut with it, they turned as fast as they do in reverse. On the ground the cart does go in forward. Still very slow, and it still squeals, but it does move, which is an improvement. Not sure what this points toward. Can the brushes wear in one direction and not the other?

[cgtech]

I would be inspecting the motor next. With rear of cart hoisted, You can test it on the cart by removing all four wires, installing a cable sized jumper between any A terminal and any S (or F) terminal. Then hook a car battery to the two unconnected terminals, reverse battery terminals to reverse direction.

[kjewer1]

Thanks again. The only problem with that is that with the tires up in the air I can't tell the difference between forward and reverse, it needs a load. Maybe I could drag the brake. I'm pretty sure at this point though it has to be the motor. If it turns out to be the motor, what are my options for fixing it? Are these things serviceable in a decently equipped home shop? Take it somewhere for rebuild? Replace it?

[cgtech]

There probably is a motor rebuilding shop in your area, they usually specialize in starters and alternators, but often can rebuild any brushed dc motor.

[kjewer1]

Sounds good. Unfortunately though I was running it again with the wheels off the ground after swapping the F&R wires back, and got a loud snap and the wheels locked up. Won't roll around now. Got some smoke and burning smell at the same time. Coming from the F&R area, which could also be the controller. Smelled like burnt electrical. 1 step forward, 2 steps back.

[cgtech]

Might as well go ahead and remove motor, see first hand whats up. Series carts are more likely than sepex carts to survive total motor failure, so you could get lucky on that (but funny smell says maybe not).

[kjewer1]

I finally got around to pulling that motor out. It's totally smoked. The insides poured out in powdered form. Looks like it ate some brushes and mangled the internals. I'm assuming something shorted at that point and caused the smoke from the controller area. I'm also assuming this can't be rebuilt since the guts are so torn up, but I wouldn't be offended if someone told me I was completely wrong about that. :)

I guess I'm in the market for a cheap 10 spline motor/controller. If anyone has any suggestions I'm all ears. Otherwise, thanks again for the help! I just wanted to update the thread with the final outcome.