External Power connector and winter starting

[rbalister]

I've got a '79 PA-28-181 and am trying to track down some power issues, specifically slow cranking in winter. Typical answer for this situation is bad battery. As a result, I connected a known good battery (it was in the car I drove to the A/P) to the external power port with the master OFF. Once connected, I heard the requisite "Thunk" from the external power relay being pulled in. I did try to start with the external battery connected and the master OFF and still got slow cranking. The other clue is that the panel voltmeter showed 11.9V while a voltmeter showed my car battery at 12.7V. I did check the battery contactor and got 0.1V drop across it. I still need to check the master contactor and associated stack-o-nuts.

The last time I flew was at night and I noticed all of the panel lights came on again when I connected the external power. Again, this was with the Master Switch OFF. I didn't think it was odd until I studied the schematics later. At the time I was just following wires. Looking at the attached schematic, which is supposed to represent my A/C, I can't figure out how the master relay could have been pulled in to power the panel lights without the master switch being on. Same goes for the battery relay. The other clue is that my aircraft has had the Bogert copper cables installed. I'm starting to wonder if when they were installed, the wiring was changed to match the later model Archer.

Is the behavior I'm seeing for the external power normal for this vintage, or am I missing something?

rayb

 

[kshaw]

 

[rbalister]

 

[Old Jim]

 

[rbalister]

 

[PaulR]

 

[Dennis]

 

[rbalister]

 

[Dennis]

 

[rbalister]