I see folks in this thread are referencing two different Garmin installation manuals... 190-02207-A1 rev2 (AML STC) and 190-02207-00 rev2 (TSO). I have both if you send me a message on this forum.
A bottom line about the two power pins is that both IMs say "All power leads and ground leads are required." Ref 190-02207-A1 rev2 page 88, note 3 and 190-02207-00 rev2 page 11-3, note 1.
It's common practice across manufacturers to use multiple power pins.
- I've always thought the use of multiple power pins was due to pin current capacity but GPS 175 max current at 14V is only 0.9A. Maybe there are a couple reasons, redundancy and current capacity.
- Bob Nuckolls teaches us to use lengths of wire as ballast resistors to balance the load through D-Sub pins. Here he speaks to Size 20 pins (0.040" diameter) with 22 awg wire. The GPS 175 62-pin connector uses Size 22D pins (0.030" diameter). The GPS 175 manual does not show such ballast resistor wire lengths.
- Unfortunately, multiple power pins can lead some installers to believe the pins are diode or'd which is some cases they are. I suspect in general if the pins are physically adjacent they are not diode or'd but one always needs to find this explicitly stated in the installation manual. The pins in the GPS 175 are clearly not diode or'd since they are shown connected in parallel external to the connector.
View attachment 5307View attachment 5309 is that both IMs say "All power leads and ground leads are required." Ref 190-02207-A1 rev2 page 88, note 3 and 190-02207-00 rev2 page 11-3, note 1.