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Old 04-18-2014, 06:46 PM   #1
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Tiffin Owners Club
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Alternator Grounding

I believe I have had a bad ground somewhere as the batteries were not charging much past 12.4v.
I ran a ground wire from the back of the alt to the frame and now my batteries appear to be charged at around 14.4v.
My question is: Do it hurt anything to run the ground wiring directly from the back of the alt to the frame?

Thanks, Bob

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Old 04-18-2014, 06:50 PM   #2
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No everything is right, the main problem found in a lot of cases with these coaches is poor ground connections or no grounds.
Cure the ground problems a lot of things would go away as to problems.

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Old 04-18-2014, 07:10 PM   #3
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Some of this stems from the fact that the average person does not understand the importance of a ground. When a switch is turned on and current flows from a battery or alternator to its load those electrons have to get back to the negative side of the battery (I'm not going to go into does current floe from + to - or from - to + that's not really important for this discussion) If there is not a return path for electrons to flow is creates a voltage drop and loss of voltage, current and overall efficiency. The negative or ground side is equally as important as the positive side. Most don't look for or even consider looking for a ground path.

Also the fact that many devices either don't use a ground wire or also rely on the chassis of the load bolted to the metal frame which is grounded (we hope).

The best story (VERY TRUE) happened like this. My assistant principal came to me with an intermittent no-crank condition that had been going on for about 3-4 months. He had it in to 3-4 shops with no success. He had the battery replaced 3 times and had two alternators installed but would still get stuck with a no crank situation. We were studying this stuff so I went over it with the kids in class and put two on it. Within 5 minutes they came back with the problem diagnosed.

The negative battery cable connection to the block was loose. The engine would move on its motor mounts because of engine torque and it would not keep a good connection. They removed the bolt, cleaned the terminal, installed two clean washers and torqued the bolt. Problem solved.

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Old 04-19-2014, 08:18 AM   #4
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A bad alternator ground can cause all sorts of interesting things to happen.. Been there, Done that. Fixed it with a "Star" type lock washer under an alternator mounting bolt.

Can it hurt anything running a ground wire to the frame?

For quite some time I wondered why Ham Radio gear often comes with fuses in both the POSITIVE and NEGATIVE leads Well. the reasonh is this....

They are worried that since many times we hook the power leads directly to the battery starting current may try to flow via the radio's other grounds should the battery negative cable fail... That would fry the wires in most cases.

This may apply to your case as well.

That said.. Many RV type alternators are fully capable of powering a starter motor even without battery aid.. And thus will not have any problem dealing with the flow.
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Old 04-19-2014, 09:11 AM   #5
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Starter motor powered by alternator...

If not running alternator not moving.

If running starter not needed...

But the factory jumpers from block to frame have caused many issue.
Tony & Lori
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Old 04-19-2014, 09:23 PM   #6
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Thanks for all the replies that confirmed what I thought.


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2008 Honda Civic EX (Toad)
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