[Wanderman]

Hi All,
 Was just troubleshooting my 12V Air Compressor in the Aquahot bay. I traced a bunch of wires through some looms into this silver box. No markings on it. Upon closer inspection and disassembly it looks like it has some burn spots. Back probing the plug shows Red wire is 12v Hot and the one next to it is 12 Neg. The other two have about 1 volt less on them but appear to be both Positive.

Any idea what this does??

I believe the fuse for the 12V compressor is under a carpeted box velcroed to the wall in a driver's side bay across from my inverter mountings.

Thanks!

[kaptain]

This looks like an electronic logic board that controls when the 12v air compressor turns on or off.
The 4x black 3-leg secured by hex-screws on top of the board, marked as ST TIP32 are 4 power transistors, https://www.st.com/resource/en/datasheet/tip32c.pdf
The multi-legged IC marked as P9336 is a binary counter, which my guess is that it compares the signals from the pressure sensors, so it turns on/off which power transistor (thus kicking on/kicking off the compressor).
The fact that it uses 4 power transistors instead of just 2, it probably has reverse-compression also, i.e. When pressure is too high to a dangerous value that is stored in EPROM, it activates two of the 4 transistors so actually takes air away from your system (via activating the relief valve or by reverse rotating the compressor).
The rectangular component marked "Program 51" is likely an EPROM that stores certain values that the manufacturer set for trigger values. It's not a complicated controller, and likely it will not produce an error code or display when encounters fault.
The burn marks are no big deal, it's just normal aging when boards get older, especially for resisters that generate heat. 
If you suspect the burn mark caused some damage, just use a multimeter to measure the resister according to its marking. You can find on the Internet what the color code rings corresponding to the supposed to be resister value.

[Richard]

Joe, the Square D well pump switch turns the air compressor on and off.

Rick, do any leads come out of the box and attach to probes at the bottom of the waste tank?

[folivier]

Following Richard's thinking, do any leads connect to the freshwater tank or possibly a fill valve to provide auto fill/cutoff?
Of course there is no telling what a previous owner added to a coach, so it could be whatever going to wherever.

[Wanderman]

So after some further examination... It appears that it MAY go to the Waste water tank... or to the Aquahot itself which is directly in front of the tank. All the wires are covered by a plastic sheath, so I have some work to do to track them all. I hae to figure out what's up with my 12V compressor. I have a new one if need be, but I suspect there is no power going to it.

Ran out of time. The story of my(an most everyone's) lives.

[kaptain]

Use a wire tracer, which costs about $20 on Amazon, you should be able to find whatever device this board controls.

[Wanderman]

I have several wire tracers.. Just have to get in there and trace it. Access is very difficult as it goes between the Aquahot and the tank.

I'll do my best!

[Richard]

So, if it goes to the waste water tank, Newell used a system of passing current through the waste water as a deodorizing system. You had to put salt into the waste water. The current disassociated the sodium from the chlorine in the salt. The chlorine was supposed to help with odor control.

I think Michael Day @"Fulltiming" has this system also, perhaps he can chime in.

[Wanderman]

Richard,
Now that sounds interesting and fits with the electronics description from kaptain. It's really difficult to get in there and trace wires. More so because I have the AH running on electric and it's right next to the 240v element wiring!

It's raining today, so it will wait a bit. I did discover that it appears only 2 wires (both red) are attached to the Square D pressure switch.. That's a bit easier to get to and would explain why it isn't working

[folivier]

I had the odor control system in my '93 but don't remember seeing the box. It sounds similar to a saltwater chlorinating system used in a swimming pool where it produces free chlorine radicals from salt. Don't think mine ever worked properly.