Connector not charging toad battery

[Arthur Gray]

I have two Wayfarers and both have had the same issue. The seven pin connector is supposed to supply 13 volts vis terminal #4, to the tow car. The 13 volts is to keep the towed car battery fully charged, while in transit. Ours does not, and the result is a dead car battery, at the end of the trip. Fuse, #13 in the coach is fine. This is a Sprinter chassis. Anyone have a solution?

[alank]

Here is the wiring for a 7 pin connector as looking at the coach. See if your cap has this diagram on it. I would say #1 is the 12V pin. If you hook your battery to #4, it's probably dead long before the end of the trip. I'm surprised you didn't have bigger problems. Did you get this pin#4 idea off the internet somewhere?

[B52Rnav]

If you have used VOM to confirm signals on the 7 way connector and the 12v signal is not active, next step is to try to confirm that all the wires on the 7 way are actually connected. On our '14 Allegro, Tiffin did not connect the 12v, so my installer ran a dedicated wire from coach battery to the connector. Also make sure all grounds are good. VOM is your best friend in debugging these connector issues.

[SamKVA]

Originally Posted by alank

Here is the wiring for a 7 pin connector as looking at the coach. See if your cap has this diagram on it. I would say #1 is the 12V pin. If you hook your battery to #4, it's probably dead long before the end of the trip. I'm surprised you didn't have bigger problems. Did you get this pin#4 idea off the internet somewhere?

This picture, everything I've seen and how our RV/TOAD are wired shows pin #4 as the Aux 12+ Charging pin or in the picture, just labeled "+". Pin #1 should be ground.



Sam

[alank]

You may be right, I may be counting from the wrong spot. Your advice on using a voltmeter is the best.

[Lt Dan]

This may be a dumb question, but is your toad wired with a charge line or charging device to its battery from the connection? Even if the trailer/toad connection has power there has to be a connection to the battery.

[Crasher]

Originally Posted by Lt Dan

This may be a dumb question, but is your toad wired with a charge line or charging device to its battery from the connection? Even if the trailer/toad connection has power there has to be a connection to the battery.

Good thing to check. A lot of Toads are not wired to charge. None of mine have been, but my battery does not discharge, even after a 5 day trip.

[garykk]

1st, have you checked if you actually have 12 volts at the RV receptacle with the key on?
Do you have a dedicated hot wire and ground from there to the toad battery?
If so, the battery in the toad should be charging unless there is a large draw on the toad when being towed. I had a similar problem when I towed a later model GMC and the 12 volts from the coach was not enough. I then installed a toad charge from ISL that solved the problem.
Also what tow vehicle are you using, does it have LED tail lights and what aux brake are you using?

[B52Rnav]

Not to start another thread ,but. Do not be confused)deceived by the colors in the diagram I have a half dozen wiring diagrams that all reflect different colors. Use your VOM and verify which signal is which. Look at wiring diagrams for toad side and be even more confused. Use that VOM!

[Arthur Gray]

To continue, ground is good and the line with the connector is wired to the coach fuse box. As this is a Class C, wiring is probably different than your rig. Do do make sense, though, as my previous Class A was similar to your rig.

[Arthur Gray]

Originally Posted by B52Rnav

If you have used VOM to confirm signals on the 7 way connector and the 12v signal is not active, next step is to try to confirm that all the wires on the 7 way are actually connected. On our '14 Allegro, Tiffin did not connect the 12v, so my installer ran a dedicated wire from coach battery to the connector. Also make sure all grounds are good. VOM is your best friend in debugging these connector issues.

Good point, I will check this. Seems strange that both of my Wafarers have the same problem. Mercedes is not much help, even though the chassis is theirs.

[Arthur Gray]

Originally Posted by garykk

1st, have you checked if you actually have 12 volts at the RV receptacle with the key on?
Do you have a dedicated hot wire and ground from there to the toad battery?
If so, the battery in the toad should be charging unless there is a large draw on the toad when being towed. I had a similar problem when I towed a later model GMC and the 12 volts from the coach was not enough. I then installed a toad charge from ISL that solved the problem.
Also what tow vehicle are you using, does it have LED tail lights and what aux brake are you using?

The toad brake installer did run a dedicated line from the coach to the toad system. Your diagram is just like mine, so there is no confusion as to the wiring. I have heard, from Mercedes that the coach is supposed to sense a voltage need, from the toad battery, before activating terminal #4, but I am not sure about this, as there is no way to determine this, if correct. We have a Chevrolet Equinox as the toad.

[Arthur Gray]

Originally Posted by garykk

1st, have you checked if you actually have 12 volts at the RV receptacle with the key on?
Do you have a dedicated hot wire and ground from there to the toad battery?
If so, the battery in the toad should be charging unless there is a large draw on the toad when being towed. I had a similar problem when I towed a later model GMC and the 12 volts from the coach was not enough. I then installed a toad charge from ISL that solved the problem.
Also what tow vehicle are you using, does it have LED tail lights and what aux brake are you using?

To continue, yes, we have LED lights in the toad, and maybe I was not clear, we have no voltage from terminal #4, with the coach engine running, as there should be. We have a Stay and Play brake system.

[ArtJoyce]

Your battery wiring may have a isolation relay so it only is on when the ignition is on.