12 Volt Appliances Won't Work

[Clyde9]

From: yellow8882 (Original Message)
Sent: 6/18/2007 8:14 AM

Hi Everyone!!! I am brand new to RV ownership. I think I have only been in 2 my entire life, so please forgive my very basic questions. I bought a '77 Dodge Minnie Winnie in above average condition but i don't know how to get all the appliances to work on 12v. like I'm missing a switch or something. I can run the water pump while on ac (plugged in or generator) but not on 12v. Same w/ the furnace. There is a breaker box inside do I need to flip something? They are currently both flipped to "on". Also there is a switch above and behind the driver seat that says Batt. / Man. (sorry I am not sure if that is exact and the rig is in for repairs) What is that for?
Having a great time so far... but we've only been to the beach a few miles away.
Thanks for any help, Chris



From: Easybago
Sent: 6/18/2007 8:44 AM

Welcome to the site!

If the furnace and water pump is original equipment, they require 12 volts to operate. It sounds to me like they are operating off of the converter which has a 12 volt output when you are connected to a 120 volt supply. Check to make sure you have at least two batteries.....one for the chassis and one for the coach. Mine has two for the coach but it would operate with only one. If you do have two or more batteries, check to make sure they are good and have a decent charge.

That would be a starting point and I'm sure some of the very knowledgeable folks here will offer more on this. Again...welcome!



From: ClydesdaleKevin
Sent: 6/18/2007 11:15 AM

Welcome to the group!

I'm sure you'll find all your answers here in this forum, and these folks are the best group of people!

Easybago is right...there is something going on with your converter, the coach batteries, or the wiring.

On an RV, the electrical system works like this:  You have a main AC power/shore power cord.  When you plug it in to shore power, the 120 volts goes down that wire to your converter, which is a power box with fuses and breakers and whatnot.  That power box doesn't just hold the breakers and fuses.  Inside that box are transformers and other goodies.  When you plug into shore power, there is a relay inside the box that shuts OFF power from your batteries, and then converts some of the incoming 120 volts AC to 12 volts DC to run your 12 volt systems.  The rest of that 120 volts AC is channeled through the breakers and into your systems and appliances that require 120 volts, like the air conditioner and the AC outlets in your rig.

Now, what happens when you unplug from shore power?  That little relay inside your power converter box switches over and turns your battery power ON.  Now, while your air conditioner and AC outlets won't work because they aren't getting any 120 volt AC voltage, all of your 12 volt systems, like the lights, the furnace, the refrigerator (even on propane, the fridge needs 12 volts to power the circuit board inside), and the water pump should now still run off of battery power.

Another thing that converter power box does is, at least for a "newer" unit like your 1977, is charge your coach batteries while you are plugged into shore power.  When you unplug, your batteries should now be charged to run the 12 volt systems.

So...to troubleshoot the system:

If you are plugged into shore power, do all your interior lights (which should be 12 volts ), the fridge, the water pump, furnace, etc, work?  If they do, then the part of the converter is working that converts part of your shore power to 12 volts DC...so that's all good.

If you unplug from shore power, does everything still work?

If EVERYTHING is out, including your 12 volt interior lights, then there are a couple of things that could be wrong.  First, the relay that switches to your batteries could be bad, although that doesn't happen often.  Second, the part of the converter that charges the batteries could be bad, which means your coach batteries don't have any juice in them.  Third, the batteries themselves could be either missing (common in an old rig), bad, or not hooked up correctly.  Forth, it could be something as simple as the cable terminals on the batteries could be badly corroded...try cleaning them thoroughly, or replacing them, put a charge on the batteries with an external battery charger and try checking your internal systems again....also look for loose wires and corroded ground wires going from your battery compartment to your converter.  Fifth and finally, and this was the problem in MY old 72 Futura motor home, the little relay inside the battery compartment (it looks like a small silver tin can, which could be rusty instead of silver, and has little wire terminals on the sides that make it look like the robot from Lost in Space) could be bad.  This was the LAST thing I replaced on mine, which turned out to be the culprit, since I thought its only function was to switch starting batteries and coach batteries for the engine when starting the rig...it serves that function, but is also a relay point which tells the converter that there are indeed batteries IN the battery compartment to either charge, or draw power from when needed.

Do the interior lights work when you are unplugged from shore power, but the water pump and furnace and fridge don't?  Or only some work, and some don't?

Then THAT could be a couple of other things.  First, it could just be blown fuses (the glass kind) in your converter/power box...the big relays are for AC power.  Second, it could be that a previous owner couldn't afford coach batteries or couldn't figure out how they were worked, so he simply wired the lights and other systems to the STARTING battery directly, and didn't bother to wire in the furnace or water pump to that battery.  And finally, and this is related to the second possibility, it could be that there are loose or broken wires going from your converter or the coach batteries to the systems that aren't working, while the other wires are still intact...in other words, some of the wiring is either bad, or mickey moused.

So, the first thing to check is to have someone stand by the shore power outlet you are plugged into, while you stand next to the converter...have them unplug the cord, and plug it back in a few times...each time he does this, you should hear a "click" coming from the converter...that is the relay inside the converter.  If you don't hear the click, don't panic...it could just be that the batteries aren't there, have corroded terminals, or that little robot relay in the compartment is bad or corroded....it the converter doesn't sense the presence of batteries, I don't think it will click (I could be wrong though about that part...my old 72 wouldn't click...I never tried on my 77).  Now, whether it clicks or not, go to your coach battery compartment...it should be a door/hatch on the outside, with a slide out tray (the tray might not slide out anymore if its badly corroded).  Again, I could be wrong about the location of your battery tray...I never owned or even looked at up close an older Mini Winnie class C...but it should be one of the outside compartments.  Are the batteries there?  Do they look corroded?  Clean the terminals, clean the wires going to the tin can robot relay, and check to see if the batteries are charged...if not, charge them...if they won't hold a charge because of their age, replace them with the biggest best deep cycle batteries you can afford, and wire them in the same way.  Battery compartment all set now?  Check the systems...do they work?  If no, then change that little robot relay...bring it with you to a NAPA or an RV dealer, they'll be able to match it up for you.  Everything work now?  If not, check the ground wires and all the wires going from the battery compartment to the converter, unscrewing or unbolting all the ground wires, cleaning them where they attach wherever they attach, and screwing/bolting them back down.  Everything work now?  If not, check all the glass fuses to make sure they aren't blown...you might want to check these FIRST since they are the cheapest thing to replace.  Everything work now?  If not, check your wires coming OUT of the converter going to your systems...look for broken or loose wires and bad grounds...all set?  Everything work now?  If not, then at this point the converter itself might be bad.

One last thing...if you charge or replace the batteries, and everything is now working...unplug from shore power and leave your lights on for a day.  Check your battery charge...you should have a lower charge on the batteries than when you started.  Now, plug into shore power and leave it for a day...your batteries should be back to full charge.  If they aren't, then either the part of the converter that charges your batteries is bad, or there is still something drawing a lot of power from your batteries that you'll need to locate.

Converters in our old rigs don't usually go bad, so take hope in that...lol.

If you've done everything and checked everything I mentioned, and it still won't work, then you have exhausted my little bit of knowledge, and others on this site can help you locate the source of your troubles.

Again, welcome to the group!

Kev, Patti, the Furry Kids, and Excalibur (1977 Itasca)



From: yellow8882
Sent: 6/18/2007 12:37 PM

WOW!!!! I am seriously humbled by your respones!!! That must have taken some time, and I know I can get it fixed with all that info. The battery is there and looks in good shape but I'll get it tested. So I should leave the "breakers" on the converter in the "on" position always like a home breaker. All the coach lights work and when I plug in to ac they get a bit brighter so I think the converter is working right. Does the furnace have a pilot light? Run on propane?
Thanks again, that is alot of great info.
Chris



From: ClydesdaleKevin
Sent: 6/18/2007 5:26 PM

Cool!  So, if the battery is there, the lights work, and they get brighter on shore power, then yes, the converter is doing its job.

For the furnace, it depends on what kind of furnace it is.  My old 72 rig had a DuoTherm Glenaire convection furnace...in other words, it was low budget with no fan, and you had to light it by hand...lol!

What kind do you have and does it have a separate wall thermostat?  In my 77 Itasca, we have a ducted Coleman furnace, with a thermostat on the wall in the bedroom.  That thermostat controls the fan and shuts it off or on, and also will fire up the furnace when the temp drops below where you have it set at...BUT, that thermostat will NOT light the pilot light, and if the pilot isn't lit, then the furnace won't fire up...the fan might come on, but it will only blow cold air.  You actually have to pull the cover off the furnace (the face plate) and then turn the big red knob to "Pilot"...on ours, if you push this knob in, a heating element will start to glow, and if you hold it in long enough (for the air to get out of the line and the propane to hit the pilot) you'll see a small blue flame through a clear plastic window in what looks like a Coleman Fuel cap.  You have to keep holding in the button, for at least a slow count of 15, until that blue flame will stay lit all by itself without the button being pushed.  Once it stays lit all by itself, you can slowly turn that big red knob to "On."  If you have the thermostat turned to "Off", the pilot will still light.  If you have the thermostat turned to "On", and the temperature set higher than the ambient air temperature, the furnace will go "whoosh" and it will light...and the fan will come on.  Once the ambient air temperature reaches the temperature you have the thermostat set too, the flame will go back to just being the pilot being lit...a tiny blue flame way in the back...the fan will run for a couple of minutes more, and then shut itself off.  If you turn the therostat all the way to "Off", the pilot will stay lit, although the thermostat won't go "whoosh" and the fan won't come on.  Sometimes if you just had the furnace burning and then shut the wall thermostat to "Off", the fan will still run for a few minutes...this is normal.

In order to shut the pilot off, say for the summer, you have to open that front panel and turn the red knob to "Off"...this shuts it all the way off.

Since yours is a 77 also, you probably have the same furnace as me, or one similar.  It took me a while to figure out how it worked....you can't just turn it on at the wall thermostat....you actually have to manually light the pilot, which can take a while if its been sitting a long time.  So...open that front panel, turn the knob to "pilot", and push it in...do you see a red glow in the back?  If you do, the 12 volts is operational...if not, the wiring or the fuse is blown.  Try lighting it manually...take one of those long lighters made for lighting grills, and unscrew that Coleman fuel looking cap with the clear window...push in the button and hold it in while holding a flame in the back rear corner of the furnace...it should light, even without 12 volts.  If it lights try the wall thermostat and crank it up.  Or if it will only light hooked up to shore power, you have a bad wire somewhere, or a blown fuse.

With your water pump, some previous owner may have hooked it in directly to the starting battery instead of the coach battery, although that means it should still work when you aren't plugged into AC...that also sounds like a bad wire or a blown fuse.

Good luck!

Kev



From: denisondc
Sent: 6/18/2007 6:57 PM

And we hope you will post some pictures



From: yellow8882
Sent: 6/19/2007 9:32 AM

Thanks Again!!! All this sounds pretty logical, I guess I need to have some patience and dive in! I get "Turtle" back sometime today? and leave Thurs. for our first real trip (Huntington Beach Ca. to Flagstaff Az.) so I will be testing/working on everything while we are gone. I'll get some photos while we're gone also. Thanks again you have given me enough info to keep me busy and probably get everything running. Chris



From: yellow8882
Sent: 6/28/2007 6:15 PM

Well thanks again everyone!! I don't know why I couldn't figure it out, but I seem to be able to run everything on 12v now and I understand how everything gets charged etc...