'88 mysterious blue wire

Hi All, we're back!

I got an odd one here. Observe the blue wire I am pointing at in The first picture.

This is not, I repeat, NOT the trailer brake wire. The trailer brake wire is in the second picture I am pointing at.

This mysterious blue wire comes off the main forward circuit breaker, enters with the main bundle of wires into the interior next to the water heater, then goes off on its own, going underneath the 120 circuit breaker box, and then disappears into the driver side bulkhead-panels.

Can someone tell me what does this wire power? I'm redoing the fuse protection and eliminating the ugly brown box, so I want to make sure this thing has power, but I also need to know what it is so I can label it properly. And I rather not start pulling apart bulkheads before someone might have some info.

Thanks all!

Fixit, the only other blue wire in MY trailer is the 12V supply to the refrigerator. In my trailer, it comes off one of the two CBs in the battery box.

From your description of where it runs to, I suspect that's what your's is too.

- Jack

Well dang, you're right. Goes into the Refer's heating box, that's where the 12 volt mode gets it's power from.

Thank you.

A round of applause for Jack.

Our forum members are smart and very helpful!! Jack often times draws on his engineering expertise.

Most indeed.

Now... How many amps would the refer heater pull? I see that it is (now was) hooked up to a 30 amp circuit breaker, but that was also in hooked with the main interior power wire (red wire).

The blue wire is now going to get it's own circuit fuse on the new wiring box. Considering that the max fuse in the ugly brown box was 15 amps, can I say 15 amps for the blue wire? Or should I lean more towards 20? Or keep it at 30?

The circuit diagram for a 2306 HiLo shows the refrigerator having a 30A inline fuse on that blue wire, in addition to being protected by one of the 30A CBs in the battery box. The circuit diagram for my trailer, a 1707 does not show that inline fuse, but it is fed through the 30A CB, so it has that protection.

I'd recommend you fuse it with 30A. I doubt your refrigerator pulls less current than mine.

- Jack

On almost all my RV's the fridge heater wire is too small a gauge. I replaced it with a 6 or 8 gauge dedicated fused circuit with an 8 gauge return to battery ground. No more big 1.5 volt drop when fridge calls for power. But I use propane when camping and the 12 volt setting while hauling.

Good info. I added the dedicated 30 amp fuse and it is currently running a 8ga wire, and according to the refer data tag on the outside shows the 12 volt heater draws 11 amps. So a 8ga wire should be fine, and I'm with Tomrupp that 12v for driving, and propane while at camping, and the 120v while at home or "luxury camping" (hookups).

Thank you!