12 volt issues

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fire-99

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Mar 14, 2006
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Hey everyone,
I have a 1989 Winnebago Chieftain.  A couple of days ago while on the road the alternator went out, drained everything we had.  The only way to keep it running was to run the generator to provide some juice while we found a repair shop.  Well we got the alternator fixed and she runs and charges fine but we cannot run the interior off the 12v coach batteries.  If we're plugged in or have the generator on everything works fine, once we unplug we're dead.  I've checked the battery voltage directly and it's fine, and if I use the check switch on the dash it shows good also.  I have no idea how the coach electrics work, is there a switch or something that could have burned out?  All the breakers are set, I have no idea.  Please help!

Adam
 

Steve CDN

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Adam,

Is there an inverter in your system or a voltage transfer switch that detects the source of incoming 110 VAC in your system? 
 

fire-99

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Mar 14, 2006
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Thanks for the responses,
we have an inverter in the system, the only switch I know of right off the bat is the dash mounted switch for turning on internal power.  We have that on, the lights lit up anyway, and it controls some of the stuff in the coach, furnace blower, etc.  I'll check to see if I can find another switch in the meantime.

Adam
 

fire-99

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Mar 14, 2006
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Sorry about that,
None of the 12 volt stuff will work without being plugged in.  Once I'm plugged in everything works.  I assume from this that the inverter is doing it's job, but that thing just plain confuses me.  The only thing I can think of is that maybe there is a solenoid or something that switches power from the batteries.  I don't know, I'm at a loss.  Why would the 12 volt appliances work when plugged in but not just off batteries?  The batteries check okay, maybe if I could figure out where they enter the cabin I can start checking for power.  I've got some time coming up so I can do some investigating.  But yes, once I'm plugged in and have the furnace going, if I turn off the coach switch the blower goes off, so I think the switch is working. 
Thanks for the input.

Adam
 

Karl

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Adam,

Problem might be the large fuse in the battery circuit, usually rated about 200 amps, I think. If that's blown, 12 volt stuff would work off the converter but not the batteries. Should be located in the immediate area of the batteries. Or the output of your converter is going thru a cut-over relay o.k., but when it's off (disconnected from shore power), the relay isn't switching back to batteries properly. I have no idea where that relay might be on your rig, but maybe you can listen for it operating while switching shore power on and off. 
 

RLSharp

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fire-99 said:
None of the 12 volt stuff will work without being plugged in. Once I'm plugged in everything works.

All the converters I have worked on have a transfer switch built into them which are activated by shore power. These are normally closed relays (puts the batteries in the circuit by default) which transfer 12VDC from the battery to the converter output and then to the coach circuits when shore power is present.

It is possible that this transfer switch is bad or that the contacts have become badly burned and therefore not able to conduct enough current to power your 12 V appliances. There are not many other possibilities, if your batteries are indeed fully charged. The fuse, which may or may not be present between the battery and the converter, and a bad ground are about all that is left.

Richard
 

Gary RV_Wizard

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Hmmm. This is an 89 Chieftain - may not have a combined inverter/charger such as some of you are talking about. Quite possibly it has only a 12V converter/charger to power batteries and provide 12V when on shore power or genset.  It may have a separate inverter to provide some AC power from the batteries, but I'm not even sure of that, since Adam has used the term "inverter" but talked mostly about 12V power problems rather and functions I associate with a converter and/or charger rather than an inverter.  I'm thinking Adam may be using the wrong terminology is at least part of his problem description.
 

John From Detroit

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IF all the 12 volt stuff works when you are running the generator or plugged into mains
But none of it works, and I mean none, not the inverter, not the furnance, not the isle lights not the light in the bathroom
none of it works when you don't have 120 vac present.  Then the list reads like this:

1; Battery disconnect switch (See note 1)
2: Fuse 
3: Batteries are show
4: Wireing is shot

Note 1; There are basically 4 types of battery disconnect switches.
My coach has a remotely operated latching relay, there is a control palel (in my case next to the steps actually below the floor but in the stair well, in other cases it can be most any place you have switches)  Another simpler system I will be using for the inverter circuit has a knife switch usually near the battery, still another system has a "Quick Disconnect" on the positive battery post.  And there is a rotary (knob) switch as well.  Many options here.

Here is what you should do,, First find the HOUSE batteries, (usually it's plural) as opposed to the chassis battery (usually singular) usually these are not located in the same place.  Find the POSITIVE lead, often marked with a PLUS sign on the battery,  Follow the wire, with your eyes, looking for a disconnect switch or fuse, if fuse, use a volt meter or test light to check the fuse,  by the way, use the test light to check the battery (more follows) all testing is done with no 120vac by the way as the converter will mess up the tests otherwise.

While you are there take a good close look at the NEGATIVE (-) side of the battery as well... Any time you are doing electrical work, and a good number of jobs that have nothing to do with electricity, the job procedure begins with "REMOVE BATTERY NEGATIVE LEAD"

Since this problem begin when you picked up from service... I'd almost, and I stress ALMOST, be willing to bet the technician dissconnected the negative battery lead............ and forgot to reconnect.

Back to testing... AC power off, connect test light across batteries, it should light,  Move NEGATIVE lead to chassis ground point (any metal chassis part, IE motor home frame) shoudl still be lit, if not check negative lead, if lit move to fuse, or switch  Should remain lit both sides of fuse or switch, if not check fuse or seitch.

If remote switch you will have to find the thing (See your manafacturer's manual for info) in my case the house batteries are under the entry steps, but the switch is above and to the driver's side of the stering column, in the engine compartmetn,  Yours could be anywhere. 

If the light is lit at every point near the battery you will need to find that switch, this can be a job.  but the manafacturer has given us a clue... Sometiems.  If you have a switch marked EMERGENCY START, and a partner, I can tell you how to use that switch to locate your remote switch,,, If not, then you have to use the hard way (Trace wires)

If you locate the remote switch (Assumign you have one) then again we do the test light thing, Step one is hook one lead of the test light to a good chassis ground, same as last time we did that.. Now test both sides of the switch (Actually there are 3 sides to this switch) all of them should light the light... I'll bet one does not.

If you get light, dark, light (or any combination of 2 lights, one dark) find the remote switch and operate it, you will hear teh relay click and 12 volt systems come alive (we hope) if not, apply mains power (AC power) you shoudl now see 3 lights, again try operating the remote switch, you may hear the relay click in.

NOTE: if the light is very dim when you test at the battery.. Either the batteries are shot or they are dead due to the remote switch being turnd off, not on.

But give us the results of the test light sequence and we may be able to give you more info
 

Kirk

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Lets make this as simple as possible. First of all, you need either a good meter, or at least one of those 12V test lights. A good digital meter will tell you more, but we could get by with just the test light. Start by lifting the negative cable from the battery post and hook the meter or light between the cable and the negative post of the battery. If that cable is good, you will get 12V indication. We are assuming that the battery is known good. Once we know that cable is good, then put that cable back and connect negative side of your light or meter to it and start to check for voltage at each point from the battery to the loads. When you stop finding a voltage, the problem will be between the last spot that you had voltage and the first one where it is missing.
 

fire-99

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Mar 14, 2006
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12
Everyone,
thanks for all the help.  Simple solution really, I should have known.  After tracing the battery cables looking for a fuse or something I realized they went up into the engine compartment.  I opened the hood and notice a bit box with quick fasteners on it.  Opened it up and there was another breaker box that I knew nothing about.  One of the breakers was popped, reset it and everything is fine.  So for my own future reference, 2 separate breaker boxes in the coach, plus one under the hood.  Feel so stupid, but at least it's fixed.

Adam
 

John From Detroit

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fire-99 said:
Feel so stupid, but at least it's fixed.

Well... Don't feel stupid,, Blame the sales team that showed you your motor home when you bought it (or the former owner) and failed to point out said breaker box.  My rig has fuses in a number of places.  I am still finding some of them and they gave me a decent tour....

I have a fuse panel under the dash, A second one under the hood, And a third in the hallway (House fuse box), in addition there is a 40 amp and a 400 amp fuse in the battery compartment (After market) and a fuse panel next to the driver's seat (after market, WestMountain radio product) and there will soon be a second battery compartment with another 400 amp fuse, and there is another fuse in the bedroom behind the TV (Added fuse) and... Well you get the idea, fuses all over the place

Same with 120vac breakers... I have them in at least 3 places I am sure of,, one after market, 2 OEM
 
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