I took my 27 foot 1998 Four Winds Trailer LS by Thor out for the first time this weekend. Everything seemed to be going okay except that I could not get the lights or any electic systems on the inside to work unless I plugged into my truck. Now for the strange part. The electric tongue jack and the electric slide motor worked just fine with out the truck plugged in so I know the battery is working and is only a year old. I checked the fuses and the breakers and all of them are fine. I found only one in-line fuse for the jack and it was fine. I know I am missing something somewhere and know that it must be simple a switch or fuse I am missing. Please help? I would like to add a second battery but need to get the first working properly first.
Electric problems with 12 volt system?
- Thread starter petaone
- Start date
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The only thing different you're describing is plugging in the truck. If that's the case, then the electrics on the trailer are receiving 12 volt power from the truck.
If the electrics all work with the truck plugged in, and do not with the truck unplugged, it follows that there is no power source available when the truck is not plugged in.
So, either the trailer's battery, regardless of age, is dead, or the battery is good, but there is no connection between the battery and the fuse panel.
To find out, you will need a test light or a voltmeter. First, disconnect the truck and unplug any shore power to your trailer. Next shut off anything that draws 12 volt power.
Start testing at the fuse panel. Use your meter or test light to verify that there is no power at the panel.
A voltmeter is preferred, but a test light will work OK, just not as accurate. If the test light shows power at the fuse panel or at the battery, have a helper turn on something that draws current, it doesn't matter what. If the test light goes out or the voltage plunges several volts, suspect a badly corroded connection or a failed battery. If there is no power, or the power dies under a load, next check directly at the battery.
Don't check at the battery cables where they attach to the battery, but at the posts of the battery itself. If there is no power here, remove the battery and have it charged and then tested.
If the battery shows power (12 volts on your meter, or lights the test light), then check at the cables where they connect to the battery.
This will identify any oxidized connections which can prevent the battery from supplying power to the cables. If there is power at the battery, but not to the cables, remove the cables and clean the battery posts and the cables where they contact the posts until you see bright shinny metal on both. Add some grease or anti corrosion compound on the posts and reconnect them, then double check for power through the cables and continue testing all connections between the battery and the fuse panel.
I hope this helps.
Mike D
If the electrics all work with the truck plugged in, and do not with the truck unplugged, it follows that there is no power source available when the truck is not plugged in.
So, either the trailer's battery, regardless of age, is dead, or the battery is good, but there is no connection between the battery and the fuse panel.
To find out, you will need a test light or a voltmeter. First, disconnect the truck and unplug any shore power to your trailer. Next shut off anything that draws 12 volt power.
Start testing at the fuse panel. Use your meter or test light to verify that there is no power at the panel.
A voltmeter is preferred, but a test light will work OK, just not as accurate. If the test light shows power at the fuse panel or at the battery, have a helper turn on something that draws current, it doesn't matter what. If the test light goes out or the voltage plunges several volts, suspect a badly corroded connection or a failed battery. If there is no power, or the power dies under a load, next check directly at the battery.
Don't check at the battery cables where they attach to the battery, but at the posts of the battery itself. If there is no power here, remove the battery and have it charged and then tested.
If the battery shows power (12 volts on your meter, or lights the test light), then check at the cables where they connect to the battery.
This will identify any oxidized connections which can prevent the battery from supplying power to the cables. If there is power at the battery, but not to the cables, remove the cables and clean the battery posts and the cables where they contact the posts until you see bright shinny metal on both. Add some grease or anti corrosion compound on the posts and reconnect them, then double check for power through the cables and continue testing all connections between the battery and the fuse panel.
I hope this helps.
Mike D
Gary RV_Wizard
Site Team
Your trailer may have a battery disconnect switch somewhere, which would prevent battery power from reaching anything that was not wired direct to the battery (e.g. the tongue jack). Look around for a switch (may not be marked), often near the entry door. It may look like a regularly RV light switch, since it will operate a heavy duty relay somewhere else.
John From Detroit
Well-known member
I will give you two suggestions
First: What Roamer said, I second his suggestion.. In many cases jacks and/or slide system may be connected DIRECT to the batteyr bypassing the master disconnect. This actually makes a lot of sense. If your rig is done that way then the jacks and slides run off the battery all the time
The rest of the house is connected ... differently
Usually through both a master disconnect and a master circuit breaker or fuse. Depending on the rig, motor home or trailer, make model and age, there are several different ways this is done.
For example. In another thread a motor home owner has a "Battery control center" and in this center are some 30 amp breakers,, Which were tripped, cutting off his batteries.. but jacks, and slides still worked. (My rig is wired that way too but the breaker is self-resetting)
I take it you have a trailer.. Thus you don't have the same BCC he and I have, but you may have something like it
The procedure of last resort is to take either a volt meter, Or for jobs like this I prefer a test light, and start looking for where we do, and do not, have power.
Starting at the battery test positive to negative I will describe using a test light.. NOTE LIght = about 13 volts on a volt meter)
light good, no light bad
Move the NEGATIVE clip on the test light to the chassis.. Touch probe to positive LIGHT GOOD
Follow the positive wire, if you come to a device, ANY device touch the terminal the wire hooks to LIGHT GOOD
Touch the other terminal LIGHT GOOD
Follow that wire.. Keep at it till you no longer see the light
First: What Roamer said, I second his suggestion.. In many cases jacks and/or slide system may be connected DIRECT to the batteyr bypassing the master disconnect. This actually makes a lot of sense. If your rig is done that way then the jacks and slides run off the battery all the time
The rest of the house is connected ... differently
Usually through both a master disconnect and a master circuit breaker or fuse. Depending on the rig, motor home or trailer, make model and age, there are several different ways this is done.
For example. In another thread a motor home owner has a "Battery control center" and in this center are some 30 amp breakers,, Which were tripped, cutting off his batteries.. but jacks, and slides still worked. (My rig is wired that way too but the breaker is self-resetting)
I take it you have a trailer.. Thus you don't have the same BCC he and I have, but you may have something like it
The procedure of last resort is to take either a volt meter, Or for jobs like this I prefer a test light, and start looking for where we do, and do not, have power.
Starting at the battery test positive to negative I will describe using a test light.. NOTE LIght = about 13 volts on a volt meter)
light good, no light bad
Move the NEGATIVE clip on the test light to the chassis.. Touch probe to positive LIGHT GOOD
Follow the positive wire, if you come to a device, ANY device touch the terminal the wire hooks to LIGHT GOOD
Touch the other terminal LIGHT GOOD
Follow that wire.. Keep at it till you no longer see the light
Marsha/CA
Moderator Emeritus
Petaone,
I know you are trying to work out the lack of power in your trailer; but I wanted to remind you not to leave your trailer plug plugged in to the truck as it's a direct draw and will drain your truck battery down.
Once you get the trailer lights figured out and everything is working as you want it to, you might want to consider a one-way pole (diode) on the connection to your truck battery. That way the truck battery can charge the trailer but not be drawn down.
We had a slide-in truck camper and once the camper battery was drained down, the camper would draw on the truck battery. So, we had the one-way pole/diode put on so the truck battery would charge the slide in camper, but would not work the other way draining the battery.
Just a thought.
Marsha~
I know you are trying to work out the lack of power in your trailer; but I wanted to remind you not to leave your trailer plug plugged in to the truck as it's a direct draw and will drain your truck battery down.
Once you get the trailer lights figured out and everything is working as you want it to, you might want to consider a one-way pole (diode) on the connection to your truck battery. That way the truck battery can charge the trailer but not be drawn down.
We had a slide-in truck camper and once the camper battery was drained down, the camper would draw on the truck battery. So, we had the one-way pole/diode put on so the truck battery would charge the slide in camper, but would not work the other way draining the battery.
Just a thought.
Marsha~
Gary RV_Wizard
Site Team
A simple diode alone won't do it - in order for the charge function to work, the diode would have to allow current to flow from the truck to the trailer. That's the same direction it flows when the trailer battery is low and "sucks" power from the truck battery. A device called a battery isolator is needed - its a relay with enough smarts to understand whether the truck alternator is charging and has power to spare. There is also a device called a battery saver, which automatically disconnects the truck battery if its voltage drops below some fixed point, e.g. around 12.0V. That lets you use some power from the truck battery but avoids draining it. One such product is called Priority Start and another is The Battery Brain.
Marsha/CA
Moderator Emeritus
Thanks Gary, I knew somebody would straighten me out. All I know is that it helps to prevent the trailer and the truck battery from being drawn down.
When we were pulling horses with the truck/slide in camper, we had a few friends who did not have the isolater and they woke up several days later with a dead trailer battery, as well as, a dead truck battery. I wanted to avoid that situation.
Marsha~
When we were pulling horses with the truck/slide in camper, we had a few friends who did not have the isolater and they woke up several days later with a dead trailer battery, as well as, a dead truck battery. I wanted to avoid that situation.
Marsha~
Sorry about my earlier post - The other folks who replied are correct in their sugestions and I was off base.
The testing procedure is fine, but I mis-read your posting. I didn't mean to mislead you, but I missed your point that some things were getting power, and others were not.
Follow the sugestions about the battery isolator switch or solenoid or work back from the fuse panel with a test light or voltmeter.
Mike D
The testing procedure is fine, but I mis-read your posting. I didn't mean to mislead you, but I missed your point that some things were getting power, and others were not.
Follow the sugestions about the battery isolator switch or solenoid or work back from the fuse panel with a test light or voltmeter.
Mike D
