Electrical gremlin located!

I found the cause of my electrical problems, it was — me.  No surprise there.

If you’ll recall, the problem was that when my starter cable was connected to the battery, I had no power to my radios or engine instruments.  Well the problem turned out to be a wire connected to the wrong terminal of my starter relay.  This particular wire was connected to the log on which was also the cable that went back to the battery.  That meant that this wire was always seeing 12V from the battery.  This particular wire ran back to my EXP-Bus and was connected to an input labeled STRT.  This is what the STRT input does:

“Connect to the starter switch. When power is applied to this terminal, the avionics bus is shut down, even if the avionics master switch on “ON”. This can prevent damaging radios with power surges during engine start.”

See what’s going on here now?  Since there was always 12V on this input, the radios and instruments were always off.  So, why was it connected to the same lug as the battery cable?  It’s not supposed to be.  Ah-ha!  So I moved the wire to the terminal that is connected to the key switch that energizes the starter relay, you know, where it was supposed to be connected in the first place?  This terminal only get’s 12V when you turn the switch to start the engine.  Ah…  That’s better.  Everything worked perfectly after that.

I pulled the airplane out of my hanger and it started up immediately.  For the first time I could see that I did, in fact, have oil pressure and I could see my RPMs finally.  I also took this opportunity to taxi around the airport a few times.  I brought the plane back to my hangar and shut down to check for drips.  None!  So I fired it up again and taxied over to the transient tie-downs.  I shut down and secured my tailwheel so I could do a full power run-up to check my static, wide open throttle RPM.  I found that rpm’s hit 5500 (the upper limit for normal operations) before I had even pushed the throttle in all the way.  The engine felt smooth in some ways but felt very foreign to me.  My buddies who heard the engine came running out and told me how smooth and quiet the engine sounded.   I ran out of time so I put the airplane back in the hangar.  Next time out I’ll adjust the prop to get 5000 – 5200 RPM, wide open throttle  on the ground.  After that, there’s nothing left but to fly it.

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