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Topic: 12V towed wiring (Read 288 times) previous topic - next topic

12V towed wiring

I'm new to RV'ing and towing a towed vehicle.  We recently purchased a 2015 Cadillac SRX for our toad.  It was previously used as a toad with a Falcon 2 tow bar, an air system hookup for braking, and 6 pin wiring for electrical connection.  It's obvious the 12V from the coach is NOT charging the toad as we have reached our destination with a dead car battery a few times now.  So not only is the black wire not in use, but the blue wire is also not in use as that is for electric brakes.

My question is can I use the black center wire from the 6 pin and tap into a 12V wire at the back of the coach?  If so, do I need to add any fuses to make this a safe operation?  We are 4 weeks into a 7 week trip, but I'm tired of dealing with a dead battery.  Thanks in advance, for any help.
Regards

John & Diane M
2002 U270 3610WTFS
Build 5936
Motorcade # 19117
FMCA 547896

Re: 12V towed wiring

Reply #1 –
Yes if the black wire is not in use it is fine to use as a charging wire and it is recommended to use
fuses at both ends.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: 12V towed wiring

Reply #2 –
John, I addressed the same issue.
I took care of it in a relatively simple way.  As I always drive with the coach lights on, I just tapped into the coach tail light circuit and ran that wire ( through the 6 pin plug ) to the positive terminal of my toad battery.
Now, whenever I'm whenever we're towing the toad, the tail light circuit keeps my toad charged.  And yes, I did add in inline fuse in the circuit.  It's been working fine for 5 years now, no issues.

If you prefer not to drive with your coach lights on, you'll need to find a hot only when ignition is on circuit to tap into.
Mark & Bev
2001 U295 36' Slide
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: 12V towed wiring

Reply #3 –
John, my 2015 SRX tows just fine with 6 pin lights and brakes connection, no charging hookup.

Put car into Park, turn motor off, depress latch and place into Neutral.  Never had a battery problem since 2015.

All the best
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: 12V towed wiring

Reply #4 –
I tapped into the factory hot with ignition wire, fused it before the converter and then fused it at the car. I have the Brake Buddy and it has an electric air compressor and needs charging wire to work.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: 12V towed wiring

Reply #5 –

If using a 6 pin trailer connector and it is wired properly on the coach the center connector should have 12v on it. That is what I used and put a battery maintainer which is fused between the coach and car battery.
Amazon.com: Hopkins 39332 Brake Buddy Towed Vehicle Battery Maintainer :...

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
Jeff & Carolyn
1999 36ft. U320 Foretravel

Re: 12V towed wiring

Reply #6 –
Have you checked your cars manual to see if the battery should be connected or dis connected while towing?
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel
 

Re: 12V towed wiring

Reply #7 –
I like the following setup for charging the toad battery when the coach engine is running:

Fuse at both toad battery and "source of coach chassis  battery connection". Amp rating depends on gauge of wire.

40 amp standard automotive relay:

IN from and chassis battery source (on many coaches the closest to the rear of the coach is the chassis  battery lug of the battery isolator which is connected with large-gauge wire to the chassis battery, but any source either at the chassis battery or a place connected with large gauge wire works equally well).

OUT from relay to coach trailer connection

Any ignition hot source to close the relay. And lastly ground to complete the circuit to close the relay.

I use 8 gauge wire for both the hot and the negative from battery to battery for less voltage loss. And make sure your ground/negative connection on the coach side is either to a good connection to chassis battery negative OR good clean chassis steel.

And, if you want the toad battery charged even with the ignition off, just delete the relay. So fuse at both batteries and 8 gauge wire.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020