RV sidewall blistering occurs when water infiltrates between wall layers, causing the outer skin to separate and form bubbles. Quick containment involves drilling drain holes and sealing entry points, but permanent repair requires removing damaged material and rebuilding wall layers.
Yes, you're absolutely on the right track - your testing clearly points to a PCM failure in the ground switching circuit for the drivers side coil bank. The fact that you have +12v but no ground pulse during cranking confirms the PCM isn't completing the circuit.
You can add a tachometer to your 2003 Itasca Spirit's Ford E-450 chassis by installing an aftermarket tach that connects to the ignition coil negative terminal or ECM. Autometer and VDO make excellent options that mount in a 2-1/16" gauge pod.
Ford F53 cruise control uses a 3-pin contact ring system. Bent contacts are common and can be straightened. Clean contact surfaces and check continuity while turning the wheel.
Koni shocks improve ride quality but minimally affect body roll. Sway bars are what reduce roll. Check if your Fleetwood has sway bars - adding them will make the biggest handling difference.
Replace failing N3150 with NovaKool R4500 compressor for better heat performance or Norcold N3141 for absorption drop-in. NovaKool better for boondocking with solar, absorption for propane versatility.
Replace corroded quick disconnect terminals with high-amperage automotive blade terminals rated for 30+ amps. Standard quick disconnects fail because they carry full blower motor current instead of just switching a relay.
External tank sensors fail after years from adhesive degradation. Clean and reattach with fresh 3M VHB tape, or upgrade to SeeLevel II system for more reliable readings.