I'm running 2 deep cycle batteries on my 2206 towlite
2 group 24 batteries fit but by building a new battery box I was able to fit 2 group 27 batteries

What model of refrigerator is in your camper? Is there any way you can check the 12 volt heater for amp draw? Mine draws less than 9 amps on 12 volts Maybe check for a loose connection, shouldn't be blowing a 40 amp fuse running the frig on 12volts.

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Cheers
Garyk52
DW Judy

96 24' Hi-Lo Funchaser, (99 Aliner Sofabed Sold 6/9/18)
06 Toyota Tundra SR5 Access Cab 4X4 36,000 miles and counting

I know what it's like to have a dead (single) battery after traveling for about 9 hrs. Get there and the top won't rise. Plugged into shore power and in a short while the battery powered up enough to get the top up. So after a few years of Hi Los, here's my two cents. I, like others went with two group 24s (or 27s), I went from the battery to a marine circuit breaker to the tow vehicles plug with 10 gauge wire which gave me many more amps to run the refer AND charge the batts. I also learned from the forum NOT to use the tow vehicle while trying to raise the top--it'll blow the TVs fuse. That hyd pump needs too many amps! One of the best things my DSO and I learned was not to carry too much food while traveling, stop at Ingles, Walmart just before you get to the site or, after set up, take a cruise, check out the area and then shop for food etc. I lost a fuel pump on my TV, with no way to power the TT in the FL sun. 7 hrs later we got to the site, stuff in the refer was chilled, not cold, but food would not have made it. We'll never know. Remember, this is only my two cents. Never raise the top while still hooked to the TV!
Tree

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Treeclimber
2703 Tow Lite
2002 Escalade
Bonita Springs, Fl. &
Andrews, NC

David, I think the biggest culprit is the wiring from your tow vehicle to the seven way plug at your rear bumper. I too had numerous times when I arrived at a campground and the two batteries I have were drained. As suggested on threads, I replaced the factory my my TV wiring with 12 gauge wire and I have never had another problem. 10 gauge as suggested by TreeClimber should give you a total piece of mind.

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Fantastic Wife
2005 Toyota Tundra V-8 4.7L
2705T Tow Lite
1999 21T Tow Lite

Does running your two batteries work and you can run your fridge on DC while traveling and still have power to lift the top!

It’s the only one that came New with the unit. I suspect the fuse blows when it tries to draw more power then the wires can handle. It does not blow right away, like a drive under 2 hours

Last year I started unplugging from the TV before raising the top. I think that is one possible cause for the fuse blowing. Also, by accident I forgot to turn it off auto and drove that day on gas. The fridge was ice cold, battery fully charged, no gas Oder, and fuse did not blow. I wish it was okay to run on auto, but not worth the risk!

As Tree said, trying to raise the top with the tow vehicle plugged in and sending power to the trailer's batteries is a sure way to blow the tow vehicle's trailer battery charging fuse. I learned that the hard way after blowing maybe three fuses?

Unplug the tow vehicle, THEN raise the top!

- Jack

With the proper gauge wire from your tow vehicle, your trailer batteries are charged while in transit. We run our fridge on DC while traveling and have not had any problems with dead trailer batteries when we arrive at our destination. Sometimes are drives are up to seven hours.

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Fantastic Wife
2005 Toyota Tundra V-8 4.7L
2705T Tow Lite
1999 21T Tow Lite

After trying it this year, I think you are right. As long as I unplugged from the TV before trying to raise the top, my fuse did not blow and the fridge was fine. The one time I forgot to unplug from the TV this past summer when I raised the top, sure enough, the fuse blew.