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Old 05-21-2018, 09:07 PM   #1
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Charging from TV?

Hello all,
Does anyone know if the HW27KS is setup to charge the main battery off the 7 pin from the TV's electrical system?

My 2005 Powerstroke is very sensitive to power issues and I dont want to blow the FICM.


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Old 05-21-2018, 09:28 PM   #2
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Most trucks with tow setups have the ability to provide power to the Aux pin of the 7 pin connector. There is a separate fuse and in some TVs there is a relay that only energizes the pin when the ignition is on. If you are concerned you can remove the fuse. If you are expecting to charge the battery, be aware that the length of the wire and other factors generally do not provide much more than a maintenance charge while driving.


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Old 05-21-2018, 09:36 PM   #3
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its my understanding that all 7 pins are wired for a slow charge to whatever is being towed. As stated before it is not much more then a trickle/maintence type charge.
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Old 05-21-2018, 11:45 PM   #4
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In my truck its a 30 amp 10 awg circuit. I just dont know if the pup battery is isolated with a diode or not.
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Old 05-23-2018, 10:06 AM   #5
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Sounds like you have a Ford. Typically, Ford does NOT install the necessary 30A relay in the fuse box to supply power out to the 7-pin plug. When you buy a Ford, the factory will give you a bag that has a universal brake controller harness and the relay that you need to install.

This can easily be checked with a DMM at your 7-pin. Just start the truck and check the 12V aux power pin. My 7-pin on my F150 even has the 7 pin map embossed on the cover -- which is really nice for diagnostics. Anyway, just touch the ground pin and the 12V aux pin. If you see a zero, then you probably need a 30A relay in your fuse box.

If you do a general web search, you'll find tons and tons of "no power out my 7-pin plug" posts about various Ford trucks. 99% of those are due to no relay in place. When people buy a new truck, they tend not to pay attention to a small plastic baggy with a wire and a relay ... dealers don't really explain it and the buyer forgets/loses that baggy.

Good luck.
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Old 05-23-2018, 01:25 PM   #6
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Thanks all, I do have a 2005 F250.

It looks like I do have charging through the 7 pin already. The PO used to tow a gooseneck horse trailer with it, so I'm sure they set it up.

My PUP has 2x6v GC2 batteries and they must have been a bit low. My 13 year old alternator had a tough time keeping up. Looks like I'll have to change it out soon.
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Old 05-23-2018, 01:44 PM   #7
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Both my Older F150 and my new Ram Promaster 2500 van seem to do a pretty good job of charging the TT group 24 battery during a 4-5 hour drive.
The 150 had a charging relay that did disconnect when the key was off. My Promaster van is still energized with the key off.

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