Learn from me

[Cougar Jim]

Took the trailer from storage to do some work to get ready for a trip. At night we can't have them on the street so they were parked at the club house parking lot for two days while i had to go to work. Tuesday went to start the truck and both truck batteries had only 8 volts. Road service got it started and i disconnected the trailer and drove to the Ram dealer and left it overnight. They load tested the batteries and couldn't find a problem. Yesterday when I went to pickup the trailer the tongue jack wouldn't work. The trailer battery was dead! Connecting the umbilical electrical cord made the jack work okay. Once home I removed the battery and charged it up in the garage. Everything works okay now.

So what caused the three batteries to discharge while sitting for two days?

ANSWER....A lawn chair in the basement moved and tripped the Potable water tank heater switch on!!!!!!!

[skids]

Originally Posted by Cougar Jim

So what caused the three batteries to discharge while sitting for two days?

ANSWER....A lawn chair in the basement moved and tripped the Potable water tank heater switch on!!!!!!!

I hope the water heater element didn’t burn out if it had no water in the tank. I really thought that the heater control is managed by 12 Volts to switch a solenoid for 120 volts.

[Cougar Jim]

Yes there is water in the tank. Seeing the switch lit is the only thing I can think of that caused three batteries to drain down.

[skids]

Originally Posted by Cougar Jim

Yes there is water in the tank. Seeing the switch lit is the only thing I can think of that caused three batteries to drain down.

Maybe that is the culprit. If not, I would put an ammeter across the negative battery lead and pull fuses one at a time to see which circuit is draining the system.

[Northofu1]

Hi Jim,
Propane/CO sensor comes to mind. Not sure what where other parasitic draw would come from. I always disconnect. Until I change the wiring to the disconnect in trailer this spring.
At least it was something small.

[JRTJH]

I'd do some checking on the truck's umbilical connector. On Fords and on GMs, there is an "interlock relay" that disconnects the truck 7 pin umbilical charge line when the ignition switch is turned off. That interlock is there to prevent exactly what happened in your situation.

Even with the trailer umbilical plugged into the truck, there should be no battery drain from the truck battery "UNTIL you turn on the ignition"...

If the RAM trucks are wired the same (and I suspect they are) then you may have a problem with your truck's electrical distribution system.

The "easy way" to determine if the interlock is present and working properly, is to use a voltmeter and check the "charge line" at your truck 7 pin connector. With the ignition turned off, there should be 0 VDC on pin #4. Pin 4 is the first pin "CLOCKWISE" from the keyway. Then, turn on the truck ignition and you should see 12 VDC on that pin.

On some trucks, the transmission has to be in gear for the interlock to function, on others, just starting the truck will apply voltage to the interlock.

In short, your truck battery should be wired to prevent the truck battery from discharging through the trailer, even if the unblilcal is left connected. However, many of us "always disconnect the umbilical if leaving the truck hitched to the trailer, "just to prevent a problem"...

[Cougar Jim]

JRTJH....

On my Ram I have 12+ volts even when the ignition key is in my pocket. From now on I will disconnect the trailer cord from the truck when it sits over night.