While laying out the wires for the three temperature sensors during the last work session, the two wires for the oil pressure sensor unit (P-765 (red) & E-764 (wht/yel)) were pulled back to the firewall because that is where the oil pressure sensor unit has been relocated. Rotax has begun utilizing a different oil pressure sensor (part number 456180) that has a connector socket built directly into the top of the oil pressure sensor. The new oil pressure sensor is used in conjunction with the WH-00096 oil pressure sensor harness cable. One end of the cable has a molded plug that is inserted into the top of the oil pressure sensor. The red and white wires leaving the plug are covered in what appears to be a heat shrink sleeve long enough to traverse the bottom of the engine and meet up with the main wiring run at the rear of the engine that goes to the instrument bay.
On the left the new Rotax 456180 oil pressure sensor unit, with the molded plug end
of the WH-00096 wiring harness attached, is mounted on the custom built dual mounting bracket.
I got to thinking, it may not be necessary to cut the wires on the WH-00096
oil pressure sensor harness cable just so they can be spliced onto the P-765
& E-764 wires that come from the firewall forward connector which plugs into
the RV-12's control module. The whole cable appears to be long enough to run through
the firewall grommet and routed directly to the firewall forward connector plugged
into the RV-12's control module. At this point in time, I see no reason that the P-765
(red) & E-764 (wht/yel) wires can’t be removed from the firewall forward connector
and replaced with the two wires in the WH-00096 harness coming directly from
the connector plug on the oil pressure sensor unit.
The WH-00096 wire harness for the 456180 oil pressure sensor unit
appears to be long enough to be wired directly to the firewall forward
connector that plugs into the RV-12’s control module.
The P-765 (red) wire (12 volt EFIS Power to sensor) can be removed from pin 6 of the
firewall forward connector and replaced with the red wire in the WH-00096 oil
pressure sensor harness cable. The E-764 (white/yellow) wire (pressure signal from the
sensor) can be removed from pin 15 and replaced by the white wire in the
WH-00096 oil pressure sensor harness cable. This appears to be a sound modification
which will eliminate two unnecessary splices … and in the electrical world, less
splices = better.
A sticky wicket ... keeping grounded. Because of not seeing a third wire going to the sensor, I became curious about the oil pressure sensor's grounding and looked at section 79 of the Rotax Heavy Maintenance Manual. Based on bullet notes, it
appears the oil pressure sensor units typically receive their electrical ground
from being screwed into the oil pump housing. Not being sure if the conductive Teflon
hoses will provide enough of an electrical ground for the oil pressure sensor unit (doubt it), or if a ground is truly necessary (would think it is), the logical thing to do is go ahead and provide a ground for the oil pressure sensor. So will
ground the oil pressure sensor by crimping a wire onto a ring connector and running the wire over to the grounding block
on the firewall during the upcoming “crimp fest” day.