u/Ill_Tap8755

I’m troubleshooting a SCAD TM2 external capacitance sensor on the holding tank of my 1993 Hunter Legend 35.5 and would appreciate any ideas from those with experience.
The original aluminum holding tank was replaced sometime ago, probably around 2003, with an unknown plastic tank. It measures approximately 24” × 24” × 12” tall (30 gallons).
The SCAD foil strips were installed exactly per the instructions.
• 11” long with correct 1.5” spacing and 1/2” margins at the top and bottom of the 12” tall tank.
• Smooth, flat installation with good adhesion.
• New, properly functioning TM2 monitor (I replaced the original after discovering it had a T2 channel issue and verified the new TM2 correctly displays voltage from both channels).
Here’s what I’ve measured:
• Tank nearly empty: ~1.0 V (SCAD diagnostic)
• Tank nearly full: ~1.0 V
• Shorting the foil strips together: ~4.0 V
• Pressing a silicone bag full of water against the outside of the strips: ~2.2 V
Additional observations:
• Swapping the holding and water tank signal wires between T1 and T2 on the new TM2 produces identical voltage readings for each sensor regardless of channel, confirming the monitor is functioning correctly.
• SCAD told me they typically expect about 0.2 V empty and 1.5 V full, and that shorting the foil strips should produce about 4 V (which it does).
What puzzles me is that the sensor appears to be working properly. It clearly responds to a shorted-strip test and to an external water bag, yet the actual tank changes almost not at all between empty and nearly full.
Has anyone seen this with a replacement plastic holding tank? Could the tank construction (internal baffle, thickened wall, molded rib, double-wall, etc.) prevent the sensor from seeing the liquid even though the sensor itself appears to function normally? Any other ideas?

I have exterior aluminum deck railing installed about 4.5 years ago in NW Washington State. I paid extra for the railing to be primed before black powder coating.

The coating is now peeling/delaminating in various locations. Under the failed coating there is gray/white oxidation on the aluminum. The underside of a peeled flake looks like the oxidation on the aluminum. I don’t seem to be able to post the picture.

Question for powder coaters/metal finishers: does this look like it was actually primed before powder coating? What lifespan should I expect from “industry standard” powdercoating? What is the likely cause of failure?

The affected areas are on a lightly used, north facing deck, miles from any ocean water. No salt exposure, moderate climate.

Pix are on my original post here: https://www.reddit.com/r/Powdercoating/s/eDNhCRwon1

Thanks.