Engine sensor wiring

[Blizzard]

Can the EGT,CHT and Alternator wiring be secured in the same firewall forward bundle or should the alternator cable be isolated from the other two? The ignition wires will definitely be isolated.

 

[recapen]

I separated them....
Higher amperages will cause a field that could interfere...

 

[Carl Froehlich]

The alternator output cable should not go through the firewall. It goes to the battery side of the firewall mounted starter solenoid. As such it would be inconvenient to bundle that cable.

Carl

 

[Blizzard]

The alternator output cable should not go through the firewall. It goes to the battery side of the firewall mounted starter solenoid. As such it would be inconvenient to bundle that cable.

Carl

I was just referring to the length from alternator to the firewall. Not through the firewall. That end is already connected. But I think I have a solution for the path for the engine sensor wires away from the higher load cable of the alternator. Thanks.

 

[rongawer]

Can the EGT,CHT and Alternator wiring be secured in the same firewall forward bundle or should the alternator cable be isolated from the other two? The ignition wires will definitely be isolated.

Typically, only AC wiring or high voltage DC cables - such as ignition wires, need separation from EGT or CHT wiring. With EGT and CHT, it's the differential between the HI and LO leads that provides the signal input. A 12VDC alternator B lead that is near both instrument wire pairs will have the same, yet insignificant, impact to those signals, measured in microvolts and generally well below the sensitivity of standard avionics outputs. It's always a good idea where able to provide separation, but in this case, not mandatory. For my FWF wires, I use sensor wires on one cushion clamp, and then an inverted cushion clamp for the higher current carrying conduction, such as the alternator B lead or starter cable.

You do need separation and/or shielding for single wire (grounded case) sensors.