Forum Discussion

OBSPowerstroke's avatar
Apr 03, 2017

Tank Sensor and Underbelly Repair

This is more of an update on a post I made a month or so ago about some small issues I had after getting the trailer frame repaired and reinforced. It finally dried out enough this weekend so I could crawl under the trailer to investigate.

Ever since the frame repair my tank monitor has shown the fresh water tank as full even though it's bone dry. When I pulled the belly pan under the fresh water tank, I found the culprit really quick; a melted sensor resistor array and wiring that likely got too hot during the welding work. As soon as I pulled the resistor array out so I could see it, I checked the monitor panel and it went back to showing empty as it should. Fortunately this should be an easy fix, but I wanted to verify this is the correct part I will need before I order it:

KIB K101 Replacement Tank Wire Harness

Here's a pic of the melted harness:



I now have a new project to take on, and that's replacing the coroplast underbelly for the fresh water tank. The current underbelly has seen better days since the shop that did the frame repair dropped it once already, and when I dropped it to access the tank sensor wiring, I came across this mess:



The shop that did the repair didn't reseal the edges of the underbelly, which allowed water to leak in and completely soak the batt insulation on the wet drive home, making it useless. In reality, this insulation could have been soaked like this for years, since there's no way to completely prevent water from seeping in. My plan is to replace the batt insulation with some bubble foil since this material should theoretically retain its insulating properties when wet. I also plan on recaulking the belly pan to get it as sealed up as possible to try and prevent water from re-entering.

My question is where can I find replacement a replacement coroplast sheet that measures 39" x 68", and what type of caulking should I use to button it back up? The old caulking is black, but I'm not sure the type.

Ironically, the caulking and spray foam insulation that was previously on there had to be performed as a warranty item by the dealer since the trailer left the factory with absolutely no caulking and a couple gaping holes in the frame that made the "heated and enclosed fresh water tank" a joke.
  • Correct wiring harness???
    That would depend of if you have a 'Kib' monitor panel
    Is the panel connector correct?=====tank connections are nothing special

    Coroplast....
    Should be able to find 4X8 sheets at Home Depot, Lowes OR Sign Shops (they use it and would have better options).

    Silicone caulking....just colored black

    Enternabond Tape is good for seams

    ReFlectix Insulation is a good product vs batt insulation.......Big Box Hardware Stores
  • troubledwaters wrote:
    While your at it, install Horst Miracle Probes clicky.


    If I could access the probes easily, I'd change them out in a second. The problem is the fresh water tank is secured up in the frame by welded brackets and there's not enough room to access the probes with the tank installed. My guess is the tank was installed before the flooring was put down at the factory.
  • From looking at the pic that shows the underbelly cover with the ruined insulation, it looks like they just used screws to hold this covering up. This is just from examination of the picture, so I may be totally wrong, if so please forgive me.

    My thoughts were, One, if it is just secured by screws to the frame (I am guessing from the pic) with no sealant around the edges, then no matter how well they secured it with screws, water will get in there and ruin the insulation.

    Second, if it IS secured with a sealant as well (around the edges with the screws holding it on (like a valve cover on an engine), if water were to infiltrate that area, wouldn't the combination of sealant around the edges and sag in the middle of the coroplast create a lake like area that will trap water inside? The sealant making it harder for air to circulate and evaporate the water...

    Third, Would it be advisable to drill a small hole (say 1/4 inch or so) in a couple of strategic places in the underbelly covering to allow any water that does infiltrate to have an escape route preventing it from pooling in that area? I would thing that a "weep hole" in lowest hanging part of the coroplast would allow water to drain out as it accumulated but still be small enough to keep water from flooding in (unless you park in a lake or river I guess).

    The trailer the wife and I are looking at has an enclosed underbelly, and after seeing this, it is something that has me thinking (yeah, not always a good thing) ;)

    Like I said, if I am way off base, please forgive my ignorance.

    Take Care and Check Six!
  • Thought I'd give you all a progress update. Over the weekend I replaced the melted tank sensor wiring harness and verified I now have working tank sensors again. I also rebuilt the underbelly tray for the fresh water tank.

    Knowing that it's inevitable water will leak into the underbelly due to all the holes in the frame around the fresh water tank, I decided to use foil insulation secured with headliner glue and waterproof aluminum tape instead of batt fiberglass. I also picked up an EPDM truck canopy gasket that I'll use to seal up the underbelly instead of caulking to make removal of the underbelly easier the next time around should anything in there need to be serviced. All the materials used won't be impacted by any water leaking in, so that means even though foil insulation doesn't have that much R-value, it's still going to be much more effective than the soaked fiberglass that was in there. I haven't reinstalled the underbelly yet, as I'm also installing some new auxiliary backup lights and need to run the wiring through this area. Below is a pic of the new underbelly next to the old one.



    Hope everyone had a great weekend!
  • Nice work! That's one good-looking replacement panel. I don't understand the use of fiberglass batts. They hold too much water. If you decide to replace them, I'd recommend using Roxul mineral wool batts. Waterproof, soundproof, inexpensive and can be compressed somewhat without losing their R-value (unlike fiberglass)