Can you think of any reason why the oil and fuel PSI readings would only work when the 4500 is running on internal battery?
During internal battery ops, they both read '0' with the engine not running (I can't test engine running ops as I've yet to do 1st engine start). When I switch on the ship's power, both the fuel and oil PSI readings display '--' and the hall effect amps quickly climbs to '150' (obviously incorrect). The 4500 has been out of the plane for a couple of months and was re-installed this evening. I've re-seated the the connectors on the back, checked grounds (both for the EFIS and oil/fuel sensors), and the rear ground screw and wire is installed. Otherwise, the 4500 seems to be Ok. Installed firmware is 7.10.24.
Other data points: Both the flap and aileron position indicators were not working. Both were fully deflected in one direction.
The elevator trim sensor wires were shorting together. Through careless handling, the pins had been extracted from the connector shell so that they could be removed from the HS so that final work could be completed. Everything seems to be working fairly well now. I don't know if it's related or not, but changing from internal battery ops to ship's power shows a few PSI difference for both the oil and fuel pressure indication.