Hi everyone,
Last
fall, we were able to get our hands on a 1990
Bigfoot TF-20 (5th wheel) and got in a couple of weekends worth of camping before the snow hit. I was able to squeeze in some critical fixes before we winterized it (replaced the
furnace fan motor and sail switch, rebuild the hot water tank bi-pass), and this spring I've converted the tail and running
lights to LEDs, tracked down a new spare tire, changed the
propane regulator and added a
battery cutoff.
One of the more important things I knew I needed to do before any long trips this summer was to rewire the
brakes. While I was under the trailer, I also noticed that the holding tank wiring was in pretty bad shape so I decided to replace it as well.
It will probably surprise no one that this resulted in some pretty wonky readings at our stock
Bigfoot control panel. I simply replaced the wires with new ones, but what I didn't notice was that the heat shrunk junctions included a series of axial ¼ watt resistors that ran to each of the fractional sensors (1/4 full, 1/2 full, etc.) on the tanks. As a result, the panel reads every tank as "full" regardless of how much is in it.
I'm unsure what I should use to replace these old resistors so that I can keep using the 1990 era control panel. I've noticed a lot of people online recommend the KIB K101 wiring kit, but I get the impression I need to then change the panel so it will read correctly.
Here is my understanding of the sensors (and I'm certainly no expert...this is just what I've pieced together so far). They use different resistor configurations for different tanks and I didn't think to mark which "ball of
electrical tape containing a junction with resistors" came from which tank when I removed them. I was able to go online this morning and use the colour codes on the resistors to calculate their values:
One tank was wired in parallel.
Full: Green wire - no resistor
¾: Yellow wire - 4.7k resistor
½: Black wire - 24k resistor
¼: Blue wire - 68k resistor
Another is wired in series, so each wire is soldered below the other, creating what I believe is additive resistance:
Full - Green wire - no resistor
¾ - Yellow wire - 10k resistor
½ - Black wire - 10k resistor (20k total resistance)
¼ - Blue wire - 10k resistor (30k total resistance)
My guess is that the first tank (wired in parallel) is my black and/or grey water tank because it is right below the panel. The second might be the fresh water tank and it uses smaller resistors in series to compensate for the added resistance caused by the longer wires needed to reach the back of the trailer? Would this make sense? I'm a little worried this isn't stock because the wiring harness had been cut into several times and my freshwater tank looks newer than the others.
So, my question is whether anyone has found an aftermarket holding tank wiring harness that works with older control panels? In a pinch, I could order a few sets of resistors and solder them in (and use trial and error until I found something that worked), but I'd prefer a simpler solution.
Thanks,
Jay