12v symptoms I don't understand

Wouldn't anything that was grounded to the frame have been briefly charged through the ground when the wrench touched the body?

When you created the short with the wrench there were no fuses in the circuit from the battery. Was the trailer on shore power at that time? If it was, then more of the wiring was in play, and fuses.

As described above you need to use a multimeter. Disconnect the shore power and the battery. Load test the battery. If it load tests good, reconnect it. Go to the DC distribution panel and check for voltage. Connect a temporary 12 v load here, something that draws current. If it works, move on. If it doesn't you know where to look.

You may have burned off a ground connection somewhere. Light loads, such as a fan or a light bulb may operate on lower voltage through a sneak circuit.

Be meticulous in your checking, working only with the battery and no shore power. Start at the battery and test towards the trailer. Always be sure that the circuitry behind you is good. Pay attention to the ground wires also.

Vulcaneer wrote:

scroller95969 wrote:
I have seen some circuit boards with fuses on them.

Just grasping at straws here. If you have a digital thermostat, it probably does have a slo-blo fuse in it on the thermostats circuit board. Take off the thermostat and check that fuse (continuity) with a DMM. Sometimes the show no visible signs of a problem. Replacements can be found at Radio Shack.

You may have a similar type fuse on your fridge control panel.

The fridge control board needs 12V to operate. But the fridge will not run on 12V. It needs 120V to run. The furnace needs 110V to run the fan and igniter. But (I think) it needs 12V to run the thermostat. That is why you can read the temp, without the A/C electricity hooked up. Without the thermostat, the furnace gets no signal to ignite. So without the thermostat operating the furnace will not work.

Do you have 110V in your other on-board outlets?

Probably has nothing to do with your problem....but do your GFI's test out OK?

Like I said...Grasping at straws here.

The furnace in mine is completely 12v

Use these steps.

1. Start with the battery itself. Have it tested for shorted cells.

A shorted battery can act as a very large resistor. It will eat up more power than what the converter can put out. Thus, appliances that are sensitive to specific voltages, won't get what they need to operate. Non-sensitive items may function normally, or, they could have limited to no function at all.

2. If battery is good, move on to fuses and breakers.

Do not trust a visual inspection of fuses. They don't always look blown. Test them with a meter. Don't forget the fuses / breaker outside.

3. If all fuses and breakers are good, determine the 12 volt circuits for non working appliances.

At the distribution panel, test voltage accross terminals where your fuse would plug in.

If you have good voltage, work your way towards the non working appliance.

If you don't have good voltage, work your way towards the battery.

4. Disconnect power, pull converter / distribution panel out of the wall, and look at the rats nest of wires behind it. There may be some in-line fuses that need to be checked.

5. Outside the trailer, remove access panel behind the fridge. Look for more fuses.


Hopefully, you'll find the fix on the early steps.


I had a shorted battery problem with my TC. Only thing working, was one dim light. Turn on more than one light, nothing (12 volt) worked. This was with or without shore power. All fuses checked good. I disconnected the battery and found everything worked on shore power. Just out of curiousity, I hooked my solar panel straight to the converter (no battery) and lights worked, 12 volt television worked, bath fan worked. Furnace and fridge, did not.

As pointed out earlier, the refer most likely has a fuse on the circuit board.( I know mine has ) Not sure about the furnace.

westend wrote:
Smkettner outlined the diagnostic procedure correctly. Establish where DC power is correct value and trace from there. I would remove power from the converter for testing.

+1

Find something that doesn't work and see if it is getting 12v power. If yes, it's broke or an internal fuse is blown. If not, trace back.

scroller95969 wrote:
I have seen some circuit boards with fuses on them.

Just grasping at straws here. If you have a digital thermostat, it probably does have a slo-blo fuse in it on the thermostats circuit board. Take off the thermostat and check that fuse (continuity) with a DMM. Sometimes the show no visible signs of a problem. Replacements can be found at Radio Shack.

You may have a similar type fuse on your fridge control panel.

The fridge control board needs 12V to operate. But the fridge will not run on 12V. It needs 120V to run. The furnace needs 110V to run the fan and igniter. But (I think) it needs 12V to run the thermostat. That is why you can read the temp, without the A/C electricity hooked up. Without the thermostat, the furnace gets no signal to ignite. So without the thermostat operating the furnace will not work.

Do you have 110V in your other on-board outlets?

Probably has nothing to do with your problem....but do your GFI's test out OK?

Like I said...Grasping at straws here.

beemerphile1 wrote:
Here's another thought, did you leave a wire disconnected from the battery?

That would be my guess, or a wire incorrectly hooked up.
The other issue would be where do these items get their ground? Direct short from battery positive to ground would fry a ground connection, as no fuses are in that circuit (unless the ground is fused, as it is in my trailer).

I haven't seen what voltage your 12v is. If it is low, under 11v or so some control boards may not work but the lights will, but may be a little dim.

Here's another thought, did you leave a wire disconnected from the battery?