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Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > 2006 Sunova 12V ground problem.

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Rolin

Oregon

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Posted: 09/29/21 09:28pm Link  |  Quote  |  Print  |  Notify Moderator

DC power status:
- Chassis battery is 12.6Volts
- House battery is 8.5V

Troubleshooting information:
1. Very low current from charged chassis battery to engine and gauges. Gauges light (barely) and engine will not turn over.
2. Converter/battery charger does not charge house batteries.
3. With external battery boost to house batteries the generator will not turnover.

It appears that all batteries are grounded to a buss bar welded to the frame.

I assume that the chassis frame is common DC ground for Engine, Generator, and Converter.

I tried using a jump cable to ground the batteries to another spot on the frame. It seemed to help a small amount. Could get the generator to turn over but not enough current to turn the motorhome engine over.

I would appreciate any ideas or suggestions you might have.

enblethen

Moses Lake, WA

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Posted: 09/29/21 09:37pm Link  |  Quote  |  Print  |  Notify Moderator

If connected to shore power, check the 120 volt input to the converter. Check converter output for 12+ volts DC. Check the 12 volt DC distribution panel for 12 volts DC. Look for a BAT fuse in 12 volt DC distribution panel and test it.
What is the DC negative buss bar made of? If steel, you need to disconnect all the wires, clean with strong steel brush, coat the connections with a good quality electrical de-oxidation compound and reconnect.
Test the battery connections. Put an Ohm meter lead on the post of the battery and the other lead to battery cable. Using lowest scale on meter, it should have zero ohms of resistance. Do this for each of the negative cables.
Switch meter to volts and test the battery positives in the same manner. Positive leads should have zero volts.


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CA Traveler

The Western States

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Posted: 09/29/21 10:10pm Link  |  Quote  |  Print  |  Notify Moderator

8.5V is a very dead battery. Get it charged and load tested to see if it's any good. What is the chassis battery voltage with the ignition and head lights on and dim gauge lights? The chassis battery could be very discharged. Load test it also.

Next would be to determine if the charger is now working. With 8.5V it could have blown fuses or other problems.


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Rolin

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Posted: 09/29/21 10:12pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for the reply.
I will not have access to the MH for a few days, but will verify output of converter at that time. The buss bar is steel and it is rusted. Had to remove the batteries to get access to it. It is rusted and was unable to remove the bolts which secured the battery leads. I will use a penetrating oil next time to see if I can remove them.

I was surprised that using a jumper cable to connect the battery ground to the frame did not fix the problem. Perhaps it was not making a good enough connection. Or maybe there are other issues.

Will use a Dremel tool to grind the rust off of the buss bar if I can get the bolts out.

Didn't know if I was missing something. Seems like everything points to a ground problem, but maybe I am not seeing the forest because of the trees.

CA Traveler

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Posted: 09/30/21 08:15am Link  |  Quote  |  Print  |  Notify Moderator

A 8.5V battery is likely toast. 12.6V indicates a charged battery IF THE BATTERY IS ANY GOOD. You might have bad/weak cells. Get the batteries load tested. They should float charge at about 13.4V

Cleaning battery connections is good but how did you reach the conclusion of a bad ground?

* This post was edited 09/30/21 08:22am by CA Traveler *

MountainAir05

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Posted: 09/30/21 08:30am Link  |  Quote  |  Print  |  Notify Moderator

Rolin wrote:

Thanks for the reply.
I will not have access to the MH for a few days, but will verify output of converter at that time. The buss bar is steel and it is rusted. Had to remove the batteries to get access to it. It is rusted and was unable to remove the bolts which secured the battery leads. I will use a penetrating oil next time to see if I can remove them.

I was surprised that using a jumper cable to connect the battery ground to the frame did not fix the problem. Perhaps it was not making a good enough connection. Or maybe there are other issues.

Will use a Dremel tool to grind the rust off of the buss bar if I can get the bolts out.

Didn't know if I was missing something. Seems like everything points to a ground problem, but maybe I am not seeing the forest because of the trees.


The bar will just rust again after you clean it. They make lug and ground bars. As stated charge both batteries and have them load test. Clean all connectors or better yet, replace them and add a few. don't forget that the engine to chassis ground cable. Post back.


ground lugs pictures

* This post was edited 09/30/21 10:02am by MountainAir05 *

enblethen

Moses Lake, WA

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Posted: 09/30/21 10:21am Link  |  Quote  |  Print  |  Notify Moderator

Dremel grinding would not be my first choice. A powered wire brush would be better. Could spray with cold galvanizing paint, then clean contact area, then coat with de-ox compound as you make connections.

Rolin

Oregon

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Posted: 10/01/21 10:53am Link  |  Quote  |  Print  |  Notify Moderator

CA Traveler,
The reason I believe it is a ground issue is:
1. All DC ground seems to be connected to the same buss bar that is welded to the frame.
2. All DC items in the motorhome (both chassis and house) are affected.
3. Engine will not turn over, no head lights or running lights
4. Generator (uses house batteries) will not turn over. House lights very dim.

However, sometimes I can focus on one problem source without considering that there may other issues. So I am trying to keep an open mind.

Rolin

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Posted: 10/01/21 11:06am Link  |  Quote  |  Print  |  Notify Moderator

MoutainAir05 and enblethen,
I will reconsider the dremel option. I have a wire brush for the dremel.
Will look for De-Ox compound

Will get a new battery ground wire and new connectors and connect to engine battery. Just work on one problem at a time. Eating the elephant in one bit increments ;-)

The engine battery was charged and in good condition.

All batteries (House and Chassis) are just one year old.

MountainAir05

New Mexico

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Posted: 10/01/21 11:58am Link  |  Quote  |  Print  |  Notify Moderator

Rolin wrote:

MoutainAir05 and enblethen,
I will reconsider the dremel option. I have a wire brush for the dremel.
Will look for De-Ox compound

Will get a new battery ground wire and new connectors and connect to engine battery. Just work on one problem at a time. Eating the elephant in one bit increments ;-)

The engine battery was charged and in good condition.

All batteries (House and Chassis) are just one year old.


The place for the De-ox compound is Amazon or a Electrical supply hose. This stuff is good and expensive. Unless you have a lot to do , really clean with the wire wheel. Unless you are close to the water or very high humidity, you might not need it. enblethen, not taking away from your suggestion.

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