I am now back from the bus, have done some trouble shooting, here are the results: I did however learn that the problem also exists when the Gen or the Shore Power is on it makes no difference.

All readings are with Engine running 1000 RPM.

I. Alternator Readings:

1. Alternator: Without Gen running: 28.9 to 29.1 V
2. Alternator : With Gen running 10.1 V
3. Alternator: With Shore Power on, 9.8 V
4. Alternator: Without Gen or Shore at Low Idle, but with full load, all lights, dash air, Blower motors, OTR, Jake Brake on 29.7

II. Isolator Readings:

1. Isolator Without Gen: 28.1 House side, 28.1 Chassis side.
2. isolator with Gen running: 28.8 House side, 25.3 Chassis side
3. Isolator with House main disconnect turned Off. 25.3 on Chassis side.

III. Regulator

1. Regulator without Gen on: 28.0 at FLD 27.6 At Ignition
2. Regulator With Gen on: 27.5 Fld. 25.3 at Ignition

I also checked the lights, tail lights, the tow package, all wires and bulbs seem fine at a glance.