Honeywell oil pressure sender on 912 engines

[cscotthendry]

Just thought I'd pass on a bit of knowledge on the new Honeywell oil pressure senders that I found out with my plane.

 

I had an intermittent problem where the oil pressure gauge would go full scale and then drop back to normal readings. The rapid and absolute nature of the gauge action suggested that it might me an electrical problem rather than physical oil pressure. What confused me at first was the gauge going full scale rather than dropping to zero. I thought that a flaky connection would make the gauge drop to zero, but it doesn't. The sender is the 4-20 milliamp type unit where more pressure produces less current to the gauge. If the wire breaks and the gauge gets NO current, it goes full scale rather than zero.

 

These senders are now supplied on new 912 series engines and require a guage that can read them. They are incompatible with gauges designed for the resistive type senders (VDO type) and have two wires coming out of them where the resistive types only have one wire.