Just thought I would share a method for finding a bad ground
or a bad connection of any type.

My just finished project was having some problems holding
a good charge on the battery. I suspected a bad ground
on the regulator since I powder coated the frame and may
have forgot to clean the paint from the regulator mounting
holes. At the battery I was only reading 12.0v when running.

To check for proper ground you could use a VOM (Volt Ohm Meter)
and measure resistance, but that is not always the best way to do
it. Since the resistance will never be zero and a possible range
to the Megohms. Most folks have a problem determining what is
OK and what is not. A 4 ohm resistance may be OK for some
low amperage system but not for a high one.

The best way to find bad grounds or bad connections is to
use the VOM and measure the voltage across the suspected connection.
This voltage drop should very close to 0 Volts for a good connection.
Since they should be at the same potential, 0v or ground in
this case. Anything over 0.1 volts or so could be a problem.

What I did is to measure the voltage from the regulator case to a known
good ground like the engine, with the bike running.

On my bike it measures about 4 volts, not good. I took the regulator
off removed the powder coat, added some star washers and reinstalled.
Now the voltage drop is 0.01v and it's charging fine.

This can be done on power cable too, like measure from the positive
terminal to the starter to check for a bad cable.

Remember this needs to be done with the circuit active.
If testing the lights, they must be on.
If testing the starter, you need to be cranking it.
Charging system the bike should be running, etc.

It's easy to see the scope of the bad connection, the math is simple.
12v - voltage drop = what you really get.

Hope this helps.
later
Declan

The test you are describing is known as a volt drop test and is taught to my auto students. I find it unbelieveable that many so called technicians can't perform this test. Simple test-Pos lead of your meter to the most pos part of circuit being tested, Black lead to most neg. I have students connect to bat pos and work their way back by connection on the neg side to isolate the problem. When the drop goes away you are one connection past your problem. Avg. drop for a complete circuit can be as much as .5 v, with .1 v per connection or conductor normally acceptable. Note I said average . If drop is slightly more yet circuit functions no repair is needed. On sensor and electronic control circuits drop is more critical as these low amp circuits will suffer from resistance. Also check for drop under similar conditions as problem occured. Increased heat will increase resisrance.:sporty:

Thanks for the handy tip!
DC

Thanks for the information. We've been having some problems lately that have to be related to a bad connection, and from what I've been reading tonight, is most likely the ground.

The wealth of information out here is incredible.

Thanks
jc