How to Test if Trailer Battery is Getting Charged from Tow Vehicle

[KJRitchie]

I've got one of those plugged into the TV outlet in the bedroom. It doesn't move off the current voltage when the TV is connected and running which confirms my statement above the 12v lead of the trailer harness in not at all connected to the trailer 12v system, only the Dexter brake controller. I found my 12v plugin meter was inaccurate compared to my voltmeter so I took it apart and found a small dial and was able to adjust the voltage reading to match my voltmeter.

My next step is to understand the 12v bus next the Use/Store relay. It has power to it when the Use/Store relay is in Store mode so its always connected to the two batteries.

My question about the buss is there an input side and an output side? There are several connections to this bus. As above, one of them was the LP detector, connected last in the line of post, far right. This allows the LP detector to have power when the Use/Store switch is on Store. The LP detector has its own fuse.

The youTube video above, the technician points to the first pole looking left to right on that buss and indicates it is from the 12v lead of the tow vehicle harness.

There is a junction box to the left of this buss. I don't remember seeing any wires running from that box to the buss.

I may disconnect the first lead on the 12v buss and see if power is lost to the buss.

I guess my question is if I connect the 12v trailer harness lead and the brake controlle 12v line to the same lead will this work. With it connected this way and with the trailer disconnected from the tow vehcile and the trailer not on shore power will the Dexter controller still draw power in run down the batteries or is in deactivated because there is no signal from the brake controller in the TV.

For electric brakes they don't activate when the trailer is disconnected so why should the Dexter hydaulic actuator.

I'm I one the right track?

Kelvin

[KJRitchie]

Attached is the wiring diagram for hooking up the Dexter actuator. Looking at the black wire from the trailer plug I notice there is a connection to the breakaway battery. In our case that's the Airstream batteries. The way my Dexter is connected, the black wire from the trailer plug goes directly to the Dexter black wire. There is no black wire from the battery + connected to the trailer plug black.

Kelvin

[dznf0g]

The schematic is a crude one. See that it shows both the AS battery AND the charge line connected to the actuator? In the real world, if they just hooked your umbilical black wire to the actuator and ended it there, you get no batt charge. There needs to be another wire from the charge line to your positive buss in the AS electrical center.

[dznf0g]

Kelvin, I am going from memory here, as my baby is down for her winter nap at the storage yard. IIRC the circuit goes like this, assuming your '08 25er is electrically like my '07 30er. The entire umbilical comes through the floor, in tact, and attaches in a black positive junction block box at the rear of the wooden electrical center. From there one wire off the charge line umbilical terminal, goes to the breaker block on the right side of the electrical center. From there, two wires are split off the breaker. One goes to the silver positive Buss and that is where the batts get their TV charge. The other goes back outside to the actuator.

I believe your installers cut into the umbilical and fed the charge line directly to the actuator, breaking the circuit to the black positive block, and ultimately to the batts. Not only will you get no charge, but now there is an unconnected wire which can back feed 12V to, potentially, chassis ground. And because, I believe the breakers are directional, they will not protect that potential short circuit.

You need to trace that charge line circuit back from the breaker block. BTW, ALL of this takes place UPSTREAM from the store switch and 12V fuse panel. (which contain no fuses in the classics...but are also breakers)

[dznf0g]

Hopefully I get this right.

Positive junction box is black box at top of pic

Positive breaker "buss" is on the right with the fat red converter wires attached

[KJRitchie]

Here is the photo of the relay with the 12v bus below the relay. The right side of the relay is towards the trailer's 12v system so when you turn off the Use/Store switch it shuts everything down. I connected the LP leak detector to that right hand post. The 12v bus below is active whenever the batteries are online. They are unaffected by the Use/Store switch.

The black 12v wire from the trailer harness is not connected to the 12v bus. Another wire is connected to it via a butt connector and that wire goes back down the same hole the trailer/TV connector cable came up. It appears to terminate at the Dexter actuator 12v wire. Other wires go back down the hole, several orange wires a blue wire.

The last photo shows where the trailer/TV harness enters under the front bed and what wires come back out. The black plastic loom is opened up to show the wires. Notice there is a black wire which appears to be the wire from the 12v trailer harness wire. The black loom goes towards the rear under the trailer.

Still no word from Airstream.

Kelvin

[KJRitchie]

One of the troubleshooting steps in the Dexter manual is to connect the white wire of the actuator to the negative of the battery and the black to the postive. The result should be the motor should NOT run.

So I will cut the direct connection of the 12v wire and attach them to the 12v buss shown above. This should allow my TV to charge my battery and the actuator should work normall when the trailer is plugged into the TV.

Kelvin

[KJRitchie]

Tonight, I cut the 12v cable and attached each end to the 12v bus. The tow vehicle now is charging the Airstream batteries. I see over 13v now on my voltmeter with the TV hook up and running. The Dexter actuator works as normal.

I attached the 12v lead to the left side of the bus on the same pole as the battery cable and the brake actuator at the other end of the bus. The yellow crimp on connectors are the cables.

I wonder why the dealer didn't do this when they swapped out the Actibrake.


Kelvin