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House vs Chassis electrical questions
Total Views: 1389 - Total Replies: 3
Aug 01 2009, 12:25 pm - By smthng


Hey all,

I'm starting on wiring up the new beastie with some sound and other gadgets, but I need a quick assist on the 12 volt stuff.  I think I'm on the right track, but I'd appreciate some confirmation or correction where needed.

We have a cheap nasty car stereo that's getting gutted.  There's a big switch next to it that is labelled "Travel" and "Park".  When the engine is running, the stereo works regardless of the switch.  When the engine is off, the stereo works when the switch is on "park".  I assume that "Travel" is wired to the chassis system, while "park" is wired to the house system.  I'm guessing that the constant voltage wire from the stereo (the one that keeps the clock and radio station memory working) is wired directly to the chassis system and isn't dependent on the switch.

If that sounds correct, I'm fairly well set on the stereo.  What I'm not set on is the amp.  I want to be able to set up the same kind of deal...  travel and parked switching, so that I'm not killing the chassis battery when parked.  The amp will be far enough away and pulling enough wattage that I don't want to use that same switch, so I'll have to set up another one somewhere.  So that begs the question of "how do I figure out if a 12 volt circuit is house or chassis?".  Do I just have to disconnect the battery for the chassis and then see if a circuit is still hot?  Is there an easier way?

Also, some general questions about chassis vs house wiring...

Is the house battery charged from the chassis (engine) electricals while driving?
Is the house battery charged when we're plugged into a 30 amp spot?
Is the chassis battery charged when we're plugged into a 30 amp spot?
Do they both share a common ground, or is there a separate ground for each?

TIA!

--smthng
http://wegofar.com/
'01 Newmar Dutch Star - No name yet, but my wife calls it the Death Star. :S
'06 Jeep Unlimited Rubicon - "Teflon" - has to go away soon. :(

'09 Jeep Unlimited Rubicon - I call it "Little Tiny Baby Jeep That Needs To Grow Up By About Four Inches", but Dasy isn't really happy about that.

'03 Yamaha TW-200 - "Little Tractor"

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Aug 03 2009, 2:46 am - Replied by: KevsKnight


I'm going to be brave and throw out some suggestions here. If we were on one of the Old People's site, I would get thrashed at my answers. However, they should be good enough for what we do ;)

The Travel/Park switch is probably what you guessed, except that it probably uses the same circuit. Probably the coach battery, but the switch will prevent a drain. I helped Cat and Bryan with theirs, and I think we just wired it hot all the time. Just turn it off if you aren't using it!

One way to tell what battery something is running off of is to kill the house batteries. You should have a disconnect for that. Mine is in the battery compartment on this coach. Kill the house batteries and see what is still running.

Is the house battery charged from the chassis (engine) electricals while driving?

Sometimes. Mine do on this coach, but others did not. If you have an inverter, you can watch that panel while the engine is running to see if there is any charge going on. I would be that there is.

Is the house battery charged when we're plugged into a 30 amp spot?

Yes. This is what the converter/charger does. Hopefully it is a 3-stage charger where it does bulk, then trickle and float charges. It should maintain a charge while plugged in.

Is the chassis battery charged when we're plugged into a 30 amp spot?

I would have to say probably not for this one. Ours is not on ours. You will probably have a "Battery Boost" switch. This is used when your chassis battery is drained after sitting for a while. It "jumps" your chassis with your house batteries.

Do they both share a common ground, or is there a separate ground for each?

Yes, they share the chassis as the ground. For the 12V, you can count on that chassis ground every time :)

Hope this helps. The 12V is a bit of a mystery, but figure it out and never be out of power again!!! :)


--kev




I have washboard abs. They are just hidden under 50#s of laundry.
Aug 03 2009, 3:03 am - Replied by: smthng



KevsKnight wrote:
I'm going to be brave and throw out some suggestions here. If we were on one of the Old People's site, I would get thrashed at my answers. However, they should be good enough for what we do ;)

"good enough" is exactly what I'm after. ;)


Quote:
One way to tell what battery something is running off of is to kill the house batteries. You should have a disconnect for that. Mine is in the battery compartment on this coach. Kill the house batteries and see what is still running.

Duh!  I should have thought of that. Thanks, that will be useful. My cutoffs (I have two for some reason) are above the door in a cabinet.


Quote:
Is the house battery charged from the chassis (engine) electricals while driving?

Sometimes. Mine do on this coach, but others did not. If you have an inverter, you can watch that panel while the engine is running to see if there is any charge going on. I would be that there is.

 

Damn...  hope you're wrong on that for my coach.  I tested the coach battery voltage after being plugged in for a week and they're down to 10.5 volts.  Not good. :(  So, I'm going to run it out to a friend's house tomorrow, which is about an hours drive.  I'll test the coach voltage before and immediate after the drive and see what I get.  That should tell me for sure.


Quote:
Is the house battery charged when we're plugged into a 30 amp spot?

Yes. This is what the converter/charger does. Hopefully it is a 3-stage charger where it does bulk, then trickle and float charges. It should maintain a charge while plugged in.

 

Erk... that might be my problem right now.  I should be seeing at least 12.5 volts for good charged batteries on the coach and I'm not.  I'm guessing I need to hunt down that converter and check it.  Unfortunately, I have NO clue where it is.


Quote:
Is the chassis battery charged when we're plugged into a 30 amp spot?

I would have to say probably not for this one. Ours is not on ours. You will probably have a "Battery Boost" switch. This is used when your chassis battery is drained after sitting for a while. It "jumps" your chassis with your house batteries.

 

You're probably right.  I have an "emergency start" switch, which is probably the same as the batter boost.  The chassis battery is a little low, but not as bad as the coach batteries, which tells me they're completely different circuits.  Also, I did some more digging and found that there's a "maintenance charger" with a 10 amp socket tucked in the engine bay for maintaining the chassis battery.  Good for me, but would have been nice if someone had thought to wire it into the coach 120v circuit.  That may be a future project.


Quote:
Do they both share a common ground, or is there a separate ground for each?

Yes, they share the chassis as the ground. For the 12V, you can count on that chassis ground every time :)


Sweet!  That makes the stereo wiring a bit easier for me. 

 


Quote:
Hope this helps. The 12V is a bit of a mystery, but figure it out and never be out of power again!!! :)


Yeah, it's a big help and gets me pointed in the right direction for some preventative maintenance before we hit the road.  I'm pretty used to finding my way around 12v systems, as I've done tons of stuff to the Jeep electrics and I'm "that guy" when someone's rig starts doing strange electrical stuff on the way home from the trail.  It's just figuring out which 12v system I'm dealing with and where they are shared that is giving me problems.

I'm sure I'll have a few more questions as I figure out what my converter is up to.  Thanks!

--smthng
http://wegofar.com/
'01 Newmar Dutch Star - No name yet, but my wife calls it the Death Star. :S
'06 Jeep Unlimited Rubicon - "Teflon" - has to go away soon. :(

'09 Jeep Unlimited Rubicon - I call it "Little Tiny Baby Jeep That Needs To Grow Up By About Four Inches", but Dasy isn't really happy about that.

'03 Yamaha TW-200 - "Little Tractor"

Aug 03 2009, 4:01 am - Replied by: KevsKnight


The charger/converter should be a big beige box pretty close to the house batteries. The converter knocks down the 120V to 12V to run the 12V stuff when you are plugged in. Maybe those with similar coaches can point you in the right direction, but I have seen them under the fridge (or other kitchen component). Mine has a place in a bay right next to the batteries.

Like I said, it is probably close to the house batteries, so start there and work out.

I will bet that "maintenance charger" is to keep up the chassis battery when on shore power.

I understand that the charger/converter is good for up to 15 years. Sure, some go longer, but if there is an issue like what you have, not a bad place to start. Check output voltage once you find it.


--kev

I have washboard abs. They are just hidden under 50#s of laundry.
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