Electrical Short

stuckinchina · 12-30-2015, 10:56 AM

I have a Forest River Flagstaff Classic pop up model T12RBST with a dead short in the electrical system. I'm sure the short is in the DC circuit #6 of the WFCO model WF-8735/8740 power converter because when I pull that fuse, the short goes away. Can anyone help me with this problem? I don't know what the #6 circuit controls but I do know that the radio, exterior and interior lights don't work when I pull that fuse.

**Bama Rambler** · 12-30-2015, 11:24 AM

Is that fuse blowing when you insert it?

Sounds like that fuse controls a lot of the power through the unit.

Have you tried unhooking the radio from the power wiring and see if it's the problem?

TimVWulp · 12-30-2015, 11:26 AM

Quote:

Originally Posted by stuckinchina

I have a Forest River Flagstaff Classic pop up model T12RBST with a dead short in the electrical system. I'm sure the short is in the DC circuit #6 of the WFCO model WF-8735/8740 power converter because when I pull that fuse, the short goes away. Can anyone help me with this problem? I don't know what the #6 circuit controls but I do know that the radio, exterior and interior lights don't work when I pull that fuse.

Hi the first place I would look is at the lights. A light bulb may have burned out and shorted when it burned out. The bulbs get very hot and may have damaged wiring insulation causing a short in the light fixture.

limblips · 12-30-2015, 11:32 AM

Quote:

Originally Posted by stuckinchina

I have a Forest River Flagstaff Classic pop up model T12RBST with a dead short in the electrical system. I'm sure the short is in the DC circuit #6 of the WFCO model WF-8735/8740 power converter because when I pull that fuse, the short goes away. Can anyone help me with this problem? I don't know what the #6 circuit controls but I do know that the radio, exterior and interior lights don't work when I pull that fuse.

Confused. If there were a dead short in that circuit, the fuse would blow unless the short was prior to the fuse, in which case none of the equipment on that circuit would work since all of the voltage would go to ground and likely you would have a melted power wire to that circuit. I think we need a better description of your symptoms to be of much help.

5picker · 12-30-2015, 11:55 AM

Quote:

Originally Posted by limblips

Confused. If there were a dead short in that circuit, the fuse would blow unless the short was prior to the fuse, in which case none of the equipment on that circuit would work since all of the voltage would go to ground and likely you would have a melted power wire to that circuit. I think we need a better description of your symptoms to be of much help.

I agree. A dead short as you describe would blow the fuse in that circuit.
I'm not sure if in your description you mean by pulling the fuse the short goes away or if you mean you are pulling the blown fuse and because the fuse was blown the short is gone.

A better explanation would be helpful.
If the fuse does in fact blow, then you will need to start checking all the items you listed that do not work that are on that circuit with the fuse blown/removed.

onetonford · 12-30-2015, 12:42 PM

He might be saying the main breaker to the convertor is blowing with that fuse in it doesn't mean he has a direct short might be a overloaded converter I.E. battery low pulling a lot of amps then other circuit adds up to trip point when you pull fuse it might drop amps enough not to trip breaker.

stuckinchina · 12-30-2015, 06:49 PM

Sorry about the lack of information in my earlier post. I'll do my best to explain what I'm finding. With the battery cables connected, and the #6 fuse in place and everything off in the camper, my battery drains extremely fast which is why I started this investigation. I've installed a brand new battery and it drains just as fast as the old one. With the battery disconnected my meter indicates a dead short to ground when connected to the positive wire that is normally connected to the positive side of the battery. That ground indication goes away when I disconnect the #6 DC fuse in the power converter panel. At the panel, I am showing a dead short on the downstream side of the fuse. The positive side of the fuse shows no short so I'm assuming the short is downstream of the power converter. The strangest thing is that the #6 fuse does not blow. I have no way of measuring amperage but it seems to me that something should blow given the amount of time it's taking to drain a brand new battery. At no time did any of the 120 circuit breakers trip nor did any fuses blow. Thanks for any help.

**Flybob** · 12-30-2015, 07:05 PM

OK much clearer now. You will not get a meaningful ohm meter reading when measuring at the battery terminals with battery disconnected. There are several things in most all RV that are always powered on unless you have a battery disconnect switch immediately after the battery. Please define what you mean by "Kills the battery fast" The Propane/CO detector will kill a full battery in a relatively short period of time ( approx a week). More than likely the detector is on fuse #6. If you are going to leave the RV unattended for more than a week, you should disconnect one of the battery terminals (I like neg terminal) or add a battery tender if you have shore power available.

stuckinchina · 12-30-2015, 07:11 PM

Thanks Flybob. My battery dies in a matter of hours, not days or weeks. I was aware of the Propane/CO detector but didn't think that was the problem because I figured it didn't draw that many amps. I have kept an automatic battery charger on it for the past few days while trying to figure out the problem. Today, I left the #6 fuse out and have seen no significant loss of voltage in my battery.

onetonford · 12-30-2015, 07:25 PM

Is your Refrigerator the Three way 12V 120V gas I know on my old fiver that was what it had and if you used the 12v side it would drain the battery in a matter of a few hours. I know some pop ups had this type of fridge but the only other thing that can pull that amount of amperage is a invertor. otherwise don't know what could pull a battery down that fast a direct short would blow fuse if not at fuse than short would get red hot in just a few seconds seen it happen once on a old gas tractor I was using shorted to gas tank and was glowing before I killed the power.

Bluepill · 12-30-2015, 07:35 PM

My RBST will drop from fully charged to half charge in two weekes with nothing on except the CO detector.

None of the information that I received upon purchase shows a wiring diagram or fuse/circuit legend. I think that you will just have to check every possible load in the camper to determine what that fuse feeds, then check the loads for a problem. It could always be a pinched wire somewhere that is not a full short, but a partial that pulls around 8 or 10 amps. Also check that the break-away switch plunger has not come out. That would give you a steady draw of about 6 amps.

The factory wiring on my unit is routed improperly under the floor. There are a number of areas where it just sits on top of a frame member. See photos

Jouncing and bouncing over the road can wear through the insulation at those points. I enclosed mine in plastic tubing for protection. You might want to do a visual check on yours.

Also, for $3.60 you can get a shunt for your voltmeter. This one reads up to 50 AMPS:

http://www.amazon.com/uxcell-Current.../dp/B00D754BYG

limblips · 12-30-2015, 07:35 PM

Quote:

Originally Posted by stuckinchina

Sorry about the lack of information in my earlier post. I'll do my best to explain what I'm finding. .

I shortened your response but it explained your problem much better. I think I now understand. Since the fuse does not blow, I can safely assume that either you do not have a true "dead short" or the fuse is highly over rated (dangerous situation). A few more questions:

1. How are you reading the short? Ohmeter? If so what range is it set to when you read the short? Normally you would look for a dead short in the RX1 mode. If you are reading through a light bulb, a transformer, or some diodes in the RX1000 or above, you will see what appears to be a short but is really just low ohms (a light bulb can be ~300 ohms, same for a transformer).

2. Is this a new to you unit or has this issue started since you have owned the unit? My battery will draw down after 3-4 days because the radio has a memory and standby mode, tank sensors and the propane monitor are always on whenever the battery is connected.

3. If the unit has just started doing this, have you added anything? Screwed anything to the walls?

4. Is the installed fuse the correct rating for the circuit?

If none of the above helps, then you must have a parasitic load from somewhere (and it may not be in the circuit you suspect). As another suggested, you will need to remove the loads powered on this circuit one at a time to determine the one that is causing the problem.

Electrical problems can be a real bear to resolve but it is satisfying when you finally figure it out (based on my 24 years as an Navy aircraft electronics tech)!

stuckinchina · 12-30-2015, 07:53 PM

You Da Man onetonford! one of my kids must have turned on the 12 volt switch on my refrigerator and didn't tell me. In fact, didn't know it ran on 12 volts. Thought is was only 110V and propane. Learn something new everyday if you listen huh? This explains the battery drain but the short is still there. Sparks fly when I plug in that #6 fuse but still doesn't blow. This doesn't bother me as long as it doesn't effect anything else and doesn't drain the battery in just a few hours.

stuckinchina · 12-30-2015, 09:32 PM

Hey Limblips, thanks for your response. Here are some answers to your questions.

1. I'm getting my readings from a multimeter set on the 200 Ohm range. I'm far from an electrician and only know when the reading goes to 0, I've got a short. That's about the limit of my knowledge.

2. The unit is fairly new to me and to be honest haven't used it much. I bought this thing so my grown kids could go camping without having to use my truck. My toy hauler is too big for their vehicles and while I didn't mind them using the toy hauler, I hated them using my truck. With the pop up, they can use their own vehicles.

3. I haven't added anything other than a battery disconnect switch as part of a remedy for the original problem of battery draw down.

4. The installed fuse is only 10 amps and as far as I can tell, it's the correct size.

Bluepill, I got under the unit the other day and checked all of the wiring underneath and like yours, they did a pretty piss poor job of it. I found the same things you did and installed wiring sheathing and tape at some of the location where the wiring was rubbing on the frame. I looked at the breakaway switch the other day and it looked ok to me. Thanks for your reply.

**Flybob** · 12-30-2015, 10:24 PM

Does your fridge have a humid weather switch to reduce condensation? If so is it on as this is an electric element that warms the perimeter to help reduce condensation. Do you have an ammeter? If so try setting for 15A or higher pull fuse #6 and carefully insert one probe in each of the two fuse holder contacts. Let us know what the current is. That may help narrow down what is drawing current. The break away switch should go directly to the battery thru a large fuse.

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