Why do I have a large voltage drop from alternator to TM battery?

[ShrimpBurrito]

I've read lots of threads that discuss problems encountered with running the fridge and charging the batteries while en route. It seems the source of this problem is typically wire of insufficient size in the TV, and that contributes to loss through resistance.

My 2005 Sequoia came with the factory tow package, and I looked underneath, and it looks like #10 wire going to pin 4 (the power circuit) and ground. Assuming a 20-foot run from the alternator to the hitch (40-foot roundtrip), I should only be losing 0.4V attributable to the wire resistance in the car. Everyone is saying the TM is wired sufficiently, and that most voltage losses are due to problems with the TV, but I am losing 1.3V with the fridge and fridge fan on. The TM voltage measurement was taken at the battery leads with the batteries disconnected.

Any ideas where I'm losing so much power? Are there specific connections in the TM that are especially prone to failure? I cleaned the TM Bargman connector, and the TV connector looks fine.

In RockyMtnRay's last post in the below thread, he says he only has a 0.2v drop between the alternator on his 03 Tundra (the pickup version of the Sequoia) and the TM battery when the batteries are fairly depleted.

http://www.trailmanorowners.com/foru...ht=wire&page=2

Granted, it sounds like his fridge wasn't on, but with my batteries at half charge and the fridge off, there's 6 amps going to the batteries. So if he only has a 0.2v drop at 6 amps, I've got a problem.

Also, when I measure the voltage at the TV battery, it is 14.1V as soon as I start the engine, but it gradually falls to 13.6V and stays there. That means I go from powering the fridge and fan and still having 1-2 amps going to the battery, to being 1 amp short of being able to power the fridge/fan, which means that amp comes from the TM batteries. Is that because the alternator isn't able to provide as much power after warming up?

Thanks,
Dave

[Bill]

First thing to determine is whether the excess drop is happening in the tow vehicle or the TM. You can unmate the Bargman, and remate it with a narrow strip of aluminum foil wedged in the 12-volt connection blade and poking out. This lets you get your voltmeter connected.

When I was struggling with this problem in my '02 Explorer, I got a copy of the wiring diagram, and discovered that the wire from the alternator to the Bargman was actually at least four separate runs, of varying sizes (#14 to #10) and four separate connectors. Yes, it was #10 when it showed up at the Bargman - but most of it wasn't. When I installed a brand new continuous run of #10 for both power and ground, my problem went away.

Bill