Electrical Question in a gas golf cart

[BadHemi2014]

In short:
Question is, if I am expecting battery voltage, say 12.6V, to a headlight, but I'm only reading about 6.4V, what is going on?
Possible short, or bad ground?
How best to narrow down the search for the issue?

This is my son's golf cart, and 1st it started blowing the fuse on the lighting circuit. I got that working (wiring all looked ok, no obvious broken insulation or cracks etc but did have extraneous wires running nowhere so cleaned it all up, replaced the key switch which was acting goofy) and no problems for a month or so.
Then one day it wouldn't start and lights didn't work. Replaced a couple things (ignitor and voltage regulator) because they looked like they'd gotten hot at some point, and found more weird wiring and cleaned that up. Lights worked, started and ran fine for a week.
Now it won't start. It won't try to turn over, key on, press the accelerator, nothing happens. Lights worked then didn't. There's battery voltage to the key switch, to the accelerator microswitch, to the solenoid. Solenoid is ok.
This is a simple machine and simple wiring, but it is a 2006. I swear I've been through literally every wire and checked grounds but obviously I've missed something.
Any suggestions as to how to narrow this down to find the problem and fix it once and for all? I'm about to just rewire the whole damn cart.

 

[GTyankee]

Put your battery on a charger while you check continuity.
You might run redundant Grounds

 

[Dean2]

If the battery is good, you most likely have a bad ground somewhere. Remember, power flows from negative to positive post so any weakness or flow interuption on the negative side will drop power to accessories a lot.

 

[BossHogg]

In short:
Question is, if I am expecting battery voltage, say 12.6V, to a headlight, but I'm only reading about 6.4V, what is going on?

I believe many golf carts are 6-volt systems.

 

[18CrewDually]

So you have a gas powered golf car. It uses a 12v system (battery) to power accessories and starting.
First establish that the battery is good. Pull it out and get it load tested if you don't have a load tester. Fully charged it should read 12.6v
Once you know the battery is good CLEAN the terminals. Don't just look at them. Clean the mating surfaces.
Try it again after the above and post results. If there's still an issue, check the other end of the battery wires such as chassis grounds and hot lead to the starter along with the other connections.
If you post what cart you have you can search for a schematic and diag for the charging voltage regulator as it could be faulty.
Only other thing I could think of without knowing the brand of cart is keyswitch / headlight switch but I don't think they're your problem.

 

[BadHemi2014]

Thank you guys. It is a new battery, it is a 12V system. It's a 2006 EZGo TXT.
I actually have the manual with schematics.
A bad ground makes sense, I'm still kind of dumb when it comes to electricity so I wasn't sure what was going on.
Over the weekend I'll remove and clean all the ground connections I can find and if that doesn't work I'll add more. I'll post back with results.

 

[BadHemi2014]

Still no luck getting this thing to start. Pulled the entire lighting harness which is a mess from previous owners.
Ignition circuit wiring looks good, grounds are good, removed each one and cleaned.
I have voltage at the solenoid, tried another solenoid, they seem to be working properly, but no voltage to starter. I'm going to get another voltage regulator to see if that might be the issue.

 

[Dean2]

Still no luck getting this thing to start. Pulled the entire lighting harness which is a mess from previous owners.
Ignition circuit wiring looks good, grounds are good, removed each one and cleaned.
I have voltage at the solenoid, tried another solenoid, they seem to be working properly, but no voltage to starter. I'm going to get another voltage regulator to see if that might be the issue.

If you have voltage at the solenoid but none at the starter, try manually bypassing the solenoid by jumping the two terminals on it. If there is voltage to the solenoid and none after it, would say the solenoid is not closing properly and that could be the small wire from the solenoid to the ignition.