Yamaha golf cart voltage regulator
 

I posted a fix for high battery charging on some Yamaha golfcarts, so this is a duplicate post from the golf cart section. See attached PDF for the gory details.

DO NOT USE THE PDF BELOW, SEE LATER POSTING FOR CORRECTED DOCUMENT

Is that sensing wire ALWAYS red with a white stripe?

This is factory wiring so I ASSUME it would be the same, however I cannot guarantee this. Unfortunately, the actual wiring diagram does not include wire color codes. If I find any other info, I will post. I have another neighbor's cart to do, and I will take photos of the voltage regulator wiring so everyone will have the POSITION of the wire on the voltage regulator plug to confirm the wiring.

I found a site with diagrams back to G1A golf carts, and all appeared to have the same wiring with the red and white tracer going to +12 vdc. NOTE: none of these diagrams indicate that actual routing of the wiring, so it is possible that some versions may have the red/white wire connected much closer to the battery, while others may have it connected like our cart after the master fuse, the ignition switch and the accelerator switch.

This would also explain why the golf cart tech I was talking to said "not all Yamaha golf carts have this problem", so that is why my writeup had a way to check and see if your cart has the problem.

Could you share that link please?

Sorry, I just used 'Yamaha golf cart wiring diagram' in a Google search.

If the connections on the voltage regulator is correct in the wiring diagram, it seems there are 3 wires connected and the middle wire is the R/W sensing wire. I have not had a chance to confirm this on my cart. Will be interesting to see what you find VillageTinker.

I wanted to clean up some of the connections at the battery. The previous owner had used multiple clamp type splices on wires connected to the + & - terminal and most had the spliced connection cut off. I cleaned it all up using butt connectors that had heat shrink as part of the connector. I also cleaned up the battery terminals. My charging voltage is now about 15.8 at full speed instead of the 18 it was previously. Is 15.8 in the acceptable range? Or is it still too high?

Voltage indicator
 

I replaced by cigarette lighter/ USB outlet with a USB outlet that has a voltage indicator included, they can be found on the internet.

Normal charging voltage for 12 volt lead acid batteries is 14.5 VDC, I would consider 15.8 to be too high. In my research, it 'appears' Yamaha has used a more or less standard factory wiring harness for decades, and the typical connections lead to the higher voltage on the battery.

I am quite aware of these devices, the problem is this is the voltage AT THE DASH, and not at the battery terminals, and due to the way the golf carts are wired I have seen 2 to 5 volts difference between these two locations. IMHO, if you want an accurate reading, add a fuse at the battery positive terminal, and run a new 2 conductor cable from the fuse and the battery negative terminal to the cigarette lighter socket, after removing the existing wiring, then use the USB converter with the voltage readout. I would use a minimum of 18 or 16 gauge automotive wire.

OOPS I made a mistake on the previous voltage regulator fix wiring diagram, it turns out the color codes for the relay sockets are NOT standardized.

The attached document (rev3) has the color codes removed, as far as I can determine the pin number IDs are standard, so I left them on.

So far I have found every Yamaha cart I have tested has the overvoltage problem, I have fixed 4 so far.