Chassis Short

[patncris]

I was under my 2011 Tiffin Breeze investigating a caution light that came on, when I brushed part of the exhaust system with my elbow. I thought something had bit me, but it turned out to be a shock. The RV is in storage, plugged into 110v to maintain the batteries.
I went to get my multimeter, and tested for AC annd DC voltages. Standing next to the coach in my sneakers, there was no voltage between me (holding the negative lead in one hand and probing with the positive lead) and any point on the chassis. And in my sneaks, I didn't feel any tingling. But repeating the test in my bare feet, I measured 8.3 volts all over the chassis. The meter jumps to 16.2 volts immediately, wherever I touch the positive lead, settling down each time to 8.3vdc. I get the same result by sticking the negative lead in the dirt, and touching anywhere on the chassis.
The stray voltage is not there when I unplug the coach from the extension cord,
nor is it present when the Genset is running and supplying power.
A tech at Tiffin suggested that the plug into which the extension cord is plugged might be wired incorrectly, but I took it apart, and all is well.
Is it possible that this normal? Doesn't seem right to me.
Muldoon

[okcnewbie]

Post #12 might help out some. Great info on the AC ground/ neutral on our RV's

"Hot" chassis - AC voltage present in chassis when on shore power

[gemert]

Originally Posted by okcnewbie

Post #12 might help out some. Great info on the AC ground/ neutral on our RV's

"Hot" chassis - AC voltage present in chassis when on shore power

Very good resource! Thanks for posting.

[ronnie_g]

IMO you are lucky to be alive.....
If you feel a tingle, NEVER try to improve the conduction by removing your shoes etc etc.
Instead isolate yourself from everything till you find the problem.
Also I would be looking at AC voltages, not DC.

[FreedomDream]

The extension cord is plugged into a source that is incorrectly wired. Use your continuity checker.

[patncris]

Thank you all for your replies.
When, subsequent to my first post, I took the Breeze for a run at highway speeds, the annunciation light went away as the diesel participant filter activated, burned out the accumulated crud in the exhaust system, and resumed normal operation. I had never seen it before, and the Operators Manual doesn't explain its function.
But that eliminated my confusion as to why the shock issue appeared at the same time as the light coming on...10 volts is an instrument control voltage, and I suspected the two were related. That's why I was under the coach in the area of the exhaust system when I first got shocked - looking for a stray sensor wire exposed or rubbing.
When I returned, I backed down the driveway to access a different wall plug and different extension cord. The stray voltages were no longer present. I'm going downtown this morning to buy a circuit tester, and see if it was the outbuilding plug or the extension cord. Again, thanks to all.
Muldoon

[TeJay]

Those type of shorts can cause many weird conditions. The strangest 12-V short happened to us 40 years ago. We bought a used 1968 Buick Opel. The wipers always stopped where they were when the switch was turned off. I just thought it was an Opel thing. Then the starter motor kept running (for a few seconds) after the engine started. That kept getting worse.
Went to the shop and started looking. Eventually found out that the PO had installed a radio antenna on the top of the front fender. They didn't put a gasket under or around the hole. Water was leaking in and running down the fender and behind the fuse block. I took the fuse block off and it was filled with green battery type corrosion. I cleaned all that and fixed the connections. Replaced all fuses and added a gasket to stop the water.

That fixed the starter continuing to run and during the next rain the windshield wipers when turned off always parked as they were supposed to do. I think what happened was called voltage crossover.

TeJay

[nothermark]

I really doubt a 10 VDC control voltage caused your tingle. It sounds more like an open neutral to ground connection. Stick a finger on each side of a 9 V battery and see how much tingle you get. OTOH you and your meter form a voltage divider when you pull the stunt you did. The meter helped limit the current and took 16 V, you got the other 104 VAC assuming line voltage was 120 VAC. ;-(

[TQ60]

Anytime you get weird things like this stop and get a volt meter and do good checks to good points of reference.

Chassis to ground is one.

Do not start or move anything or change status of things as if it is intermittent you need to sneak up on it.

Use another extension cord for utility reference and measure voltages between the points in the cord and points on the coach.

You may get 240 from hot to hot if cord on opposite phase and that is fine.

[gemini5362]

It is not an open neutral but close. You have an open ground lead in either extension cord or the ground is not connected in the receptacle. I also surmise from your post that you do not have an EMS system in your coach, or you turned it off to get power or it is faulty. The EMS system would not have allowed power into your coach with no ground. If you have an EMS system and it was not disabled then it is not working.

I have experience with this. I plugged my coach into an outlet and the EMS system disabled power from getting to my coach. I knew the outlet was wired correctly because I installed it. I just bypassed the EMS system and allowed power to my coach. Every time I was kneeling on the ground and touched the chassis frame I got a small shock. The next time i moved my coach I got ready to use the extension cord and noticed the ground pin on the male end of the extension cord had gotten knocked off. I replaced the connector. Plugged it into the same receptacle and the EMS system worked fine. I also no longer received a shock when i am kneeling on the ground and touch the MH chassis

[patncris]

Gemini 5362 - you are correct. i purchased a circuit tester, and found that the external outlet into which my Breeze is plugged has an open ground, as does every other plug in that outbuilding. Nothing wrong with the Breeze.
Now I need to find out where the power for that building is hooked up, and why it has no ground. Thanks!
Muldoon

[Gary RVRoamer]

There is still something wrong in the Breeze, because there should be no AC voltage in the chassis anyway. A proper ground in the outlet would have protected you from the shock, but it's still a ground fault. Set your voltmeter to the AC voltage scale and I'll bet you find a fairly hefty voltage to ground. More than the 10v you mentioned earlier. Do it by connecting the meter leads to the chassis and direct into the earth, not via your body!

Somewhere in the coach you have a hot or neutral wire touching either the metal part of the rig or perhaps the ground wire itself. You need to find that circuit and fix whatever device on it is causing the problem. Start by turning off AC breakers one at a time until the chassis voltage disappears. Then work through whatever is opn that circuit to find where the short is.

[gemini5362]

Originally Posted by Gary RVRoamer

There is still something wrong in the Breeze, because there should be no AC voltage in the chassis anyway. A proper ground in the outlet would have protected you from the shock, but it's still a ground fault. Set your voltmeter to the AC voltage scale and I'll bet you find a fairly hefty voltage to ground. More than the 10v you mentioned earlier. Do it by connecting the meter leads to the chassis and direct into the earth, not via your body!

Somewhere in the coach you have a hot or neutral wire touching either the metal part of the rig or perhaps the ground wire itself. You need to find that circuit and fix whatever device on it is causing the problem. Start by turning off AC breakers one at a time until the chassis voltage disappears. Then work through whatever is opn that circuit to find where the short is.

I had the exact same problem he described. I am not doubting your post. However. I do not know how they wire the AC panel in a MH is the Neutral and the Ground connect to the same bar like some houses do. Are all of the appliances in the unit have the neutral isolated from the case.

I know in my case and I believe in his also from his post. It is not a very large voltage. In reality I left mine unfixed way too long because it was not that big a shock. I actually got tired of it was the reason I started looking to fix it.

Your advice to turn off all of the breakers and then see which one has voltage is a good one unless the neutral and the ground are on the same bus bar. I know that newer breaker boxes on houses are isolated but most of the older ones were not.

[TQ60]

If not isolated then fix that NOW!

A ground buss is an in Stock item at most places that sell panels and most panels have 2 with a connector bar to make them either main or sub.