electrical mystery (BF17CB)

[Franswa]

about to replace the Magnatek power center in my Bigfoot 1997 17CB....so I tripped all the breakers and pulled all the fuses to I could identify what is fused where and what color the wires are.....before I yank the PC out.....

to make a long story short... the bathroom light, the rear "sofa" light and the light above the dinette do not appear to be fused!!! (I can pull ALL the fuses and these three lights stay on!)......when I trip the circuit breaker marked "110" that controls all the 110 plugs (except for the "micro" plug that is on it's own breaker)....the three lights go out.

I tried pulling the fixtures out to at least identify the color of the wires to maybe trace them ...no luck, everything's too tight, fixture wires fed through small hole in overhead false ceiling (they don't make it easy do they? "thanks for nuttin' BF")....no "extra wires" found/going to the PC...all accounted for...(????)

I'm thinking there must be a transformer (110>12V) "buried" somewhere (thanks again BF!)....but that don't make much sense....does it? and where's the circuit protection? I'm stumped!

Anybody have an answer to this riddle??? TIA as usual, F

[cpaharley2008]

Perhaps those 3 lights are 120v?

[Franswa]

and meter says 12.24 volts

[kb1flr]

I would either find a Bigfoot manual with schematics or call Bigfoot. Sounds like maybe a previous owner did some "custom" wiring.

Rick

[Steve Outlaw]

They are obviously not fused. Since you say they are not 110V, they have to be tied to a "hot" line somewhere that is coming directly from the battery. Perhaps they are tied to the tow vehicle's charge wire (it would still be hot even without the vehicle being hooked up, back feeding from the coach battery)

Or it could be the work of Elves or maybe Elvis...

[jeffc]

As most of the older Bigfoot information does not exist any more if I were you I would 1- Contact Grant at BigfootRV and ask/email him for his advise as a lot of the old staff still work there. I personally find the factory great to deal with for answering questions, and 2- Post this question on BOCI (Bigfoot Owners Club International) That is specific to Bigfoot owners to see if anyone could help you.

[FTTRV]

To be safe un hook the battery and shore power cord. Then everything should be dead.
Chuck

[FTTRV]

If continue to have trouble call Reace at Escape Trailer Ind. He works on older FG RV's at the factory.
Chuck

[Raz]

Originally Posted by Franswa

and meter says 12.24 volts

Where was that measured? At the light socket? Are there any DC outlets? If so, what voltage is seen there? Do the lights work when the battery is connected and the shore power is not? Raz

[Franswa]

I should have added that the lights in question work (are powered) even when the batteries are OUT of the coach...shore power plugged in, parked in my driveway, no tow vehicle involved...

lights also work when coach is unplugged and batteries are in and connected... with and without tow vehicle...

the only condition I have not tried is batteries in and then trip the breaker marked "110" that controls all 110 plugs except for "micro" plug...but that's unlikely to add anything as the lights work normally when shore power is not plugged in

voltage was measured at the light socket...lights definitely have a "factory install" look to them and I can't see any added on/connected wires after the fact by a PO anywhere (all visible wiring is in bundles and neatly strapped down)

it's a "headscratcher" alright!.....thanks for the responses

[Raz]

The Magnatek converters I've seen supply full wave pulsating ( unfiltered) DC. While incandescent lamps will work fine on this, anything electronic may not work properly. It's possible a previous owner added a filtered DC power supply wired to the 110 volt circuit to power that DC branch. When plugged in a relay connects the output of the converter to the DC distribution panel. Replacing the power supply for the converter connection at the relay is how I would do it. If the voltage at the light socket changes when shore power is connected vs battery connection, then two different sources would seem likely. A shot in the dark. Raz

[ruscal]

Francois,
I recently replaced the converter in my Scamp and discovered the same thing. All fuses pulled and front drain pump still hot. I have not investigated it yet, as my front closet is full of gear. Possibly Scamp fed the pump from the charge wire and added an inline fuse for wire protection? Mine should be easy to trace the wire since wires enter the trailer through the front cabinet and the pump is right there. On yours you could try to guess where the obvious access points would be like inside cabinets or under floor service areas etc and look for a transformer or inline fuses. It sure seems that someone fed the DC from more than one place, and doesn't seem like the factory would do that without fusing the wire. Maybe there is a tool that puts a tone on the wire that could be sniffed out to see where it runs behind the paneling?
Good luck,
Russ

[Thinh]

Originally Posted by Franswa

I should have added that the lights in question work (are powered) even when the batteries are OUT of the coach...shore power plugged in, parked in my driveway, no tow vehicle involved...

lights also work when coach is unplugged and batteries are in and connected... with and without tow vehicle...

the only condition I have not tried is batteries in and then trip the breaker marked "110" that controls all 110 plugs except for "micro" plug...but that's unlikely to add anything as the lights work normally when shore power is not plugged in

voltage was measured at the light socket...lights definitely have a "factory install" look to them and I can't see any added on/connected wires after the fact by a PO anywhere (all visible wiring is in bundles and neatly strapped down)

it's a "headscratcher" alright!.....thanks for the responses

...Without hooking up BOTH shore power AND towing vehicle, your mysterious lights still work----> that means...THEY MUST BE FED BY DC INTERNAL POWER SOURCE FROM YOUR TRAILER....IMO, this power source must be DC 12volts, either from trailer battery or some sort of smart charger. The problem now is to find out where is it? If I were you, first I would try to see that "micro plug" role what is its function and where it is connected to. The second thing is to find out from the rear socket of those lights where those wires come from. The easiest way is to loose panels/sockets' housing without disconnect any wire to find out. In your case, leave shore power unhooked, TV unhooked then with a multimeter, loosing housing of either panel or lights' sockets and start from there(@ the lights' sockets). Hopefully it helps. In electrical thing, nothing is...mysterious at all, it must came from somewhere. Just my thought...

[Jack L]

Originally Posted by P. Raz

The Magnatek converters I've seen supply full wave pulsating ( unfiltered) DC. While incandescent lamps will work fine on this, anything electronic may not work properly. It's possible a previous owner added a filtered DC power supply wired to the 110 volt circuit to power that DC branch. When plugged in a relay connects the output of the converter to the DC distribution panel. Replacing the power supply for the converter connection at the relay is how I would do it. If the voltage at the light socket changes when shore power is connected vs battery connection, then two different sources would seem likely. A shot in the dark. Raz

I had exactly the same power unit in my Bigfoot as the original photo shows. Actually this unit came from the factory with both filtered and unfiltered power supply. The blue wire on the top of the 12 V fuse panel supplies unfiltered power to the fuses on the left side and the black wire supplies filtered power to the first 3 fuses on the right. Not sure exactly why Magnatek did this but obviously they did it for years. I recently replaced the converter with a Progressive Dynamics PD4645V from Best Converter and it came with a new 12 volt fuse panel where all of the fuses supply filtered power. My existing wires are exactly the same colors as the first photo. The OP's bigfoot appears to be wired exactly the same as mine but all my lights are fused ???? I do have an inline fuse for the 12V power to the refrigerator. It is located under the seat along the forward dinette seat in the wiring harness by the front bulkhead. The only way I can make sense of the original refer. fuse is that it is 30A and the panel is only rated for 20A fuses maximum so Bigfoot used an inline fuse here.

While the converters from Magnetek were poor the 120 V side of these units was fine and usually does not need to be replaced. The PD4645 is made to fit the Magnetek unit perfectly. It is an easy installation and takes about 45 minutes.

[lonnyda]

My 1993 Bigfoot was exactly the same and had filtered and non-filtered 12v. This is likely where your lights are being powered from as it will produce 12v when your battery is removed.

I ended up replacing mine as well as the charger was not that good on my battery.

[Franswa]

but the question remains where/how is this three light circuit protected (fused)....and where does it get it's power from (there are NO visible, unaccounted for wires at the power center)

and BTW the three "filtered circuits" are there for radios and TVs that direct power from the converter would cause interference in that type of appliance....from what I've read

pic below taken off the net

[lonnyda]

My 2005 BF 17.5 also has a battery shut off solenoid located in the front left side seat compartment and also has a small fuse block there. There are a few things that are fused from here. My old 1993 BF 17 did not have this so I am not sure if yours would?

It could be that the wire supplying power to this circuit originally has been changed to splice into a hot wire from the battery directly or the hot wire coming from your converter.

I found on my 1993 that the electrical had been modified over the years so anything is possible.

Hope something there helps,

[Raz]

Originally Posted by Franswa

but the question remains where/how is this three light circuit protected (fused)....and where does it get it's power from (there are NO visible, unaccounted for wires at the power center)

and BTW the three "filtered circuits" are there for radios and TVs that direct power from the converter would cause interference in that type of appliance....from what I've read

pic below taken off the net

As I suggested earlier, measure the light socket voltage first plugged in to shore power then unplugged. If the voltages are noticeably different, then you have two sources. There is usually a relay in the converter that determines which of the two is used. Look for modifications around the relay. Soldering where everything else is crimp connecters, odd sized wires, electrical tape, wire nuts, etc.

If you read the same voltage, then the branch has most likely been wired directly to the battery. Look where the battery connects to the converter.

The fact that it runs with the fuses pulled suggests a second power supply or the circuit has been wired to the wrong side of the fuse. Check behind the fuse panel. Unplugged of course. Trouble shooting the creative wiring of others is tedious, but if you are persistent you'll find it. Raz

Edit: A caution. Filtering in circuits of this vintage is usually done with electrolytic capacitors that will remain energized after the power is disconnected. Wait 10-20 minutes so they can self discharge before pulling things apart.

[Jack L]

Originally Posted by lonnyda

My 2005 BF 17.5 also has a battery shut off solenoid located in the front left side seat compartment and also has a small fuse block there. There are a few things that are fused from here. My old 1993 BF 17 did not have this so I am not sure if yours would?

It could be that the wire supplying power to this circuit originally has been changed to splice into a hot wire from the battery directly or the hot wire coming from your converter.

I found on my 1993 that the electrical had been modified over the years so anything is possible.

Hope something there helps,

After I installed my new converter, I tore the old one apart and found a relay that was activated with 120 volts when the converter was powered up. I did not pay a whole lot of attention to what function it provided but I'm pretty sure it changed the 12 volt supply circuit from battery to converter. I hope this helps also ,

I'm really baffled by all of this. I simply can not comprehend why someone would make changes to remove fuse protection. In the photo of the power center it does not appear to be modified. A photo of the area under the seat might help to determine what's going on here.

[Franswa]

I've got two things going on here....a converter/charger that won't charge(it "converts" ok)....and this strange 3 light circuit deal (that I came across while investigating the first problem)

I've narrowed down the converter/charger problem to one of two components (relays?) in the pic below I've got power from the blue wire to the relay and power out through the blue wire again to the "unfiltered side" of the fuse panel (blue wire fastened at very top of fuse panel)....the red wire from the relay goes to the backside of fuse panel and connects to a post common with the positive post on front side (black and white wires to battery) I have no power at the red wire (this is with batteries not connected BTW)...

so to summarize... fixing existing is by all accounts not desirable...I could purchase a replacement, cartridge type, converter charger that are widely available.....buying a whole new unit however seems to be about the same cost as the "cartridge" solution....and I could locate that in a better spot (behind the seat back, left side...again see pic...would use up space wasted at the moment)

or I could just use the breaker/fuse panel part of my existing (cut the lower half of the case where the conv./charg. is and mount the thing vertically in the location described (it's a perfect fit)....and then wire a good quality charger to one of the breakers (no more converter, all 12 volt comes from batteries all the time)....that's the direction I'm leaning to at the moment...

as for the 3 light circuit...I can't see or find any "added" wires anywhere I have looked....it was either done at the factory or some DPO went to great lengths to conceal his work....

my next step will be to rework the power center as described, before cutting or installing permanently (blue "unfiltered" wire connection to black wire on fuse panel, all fuses now "filtered", on straight batt. power) hook up batteries and flip some switches....I wonder what my "mystery" 3 light circuit is gonna do!

wish me luck