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ACS "Start" position pops 10 A "Instrument" C/B

lepperly

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The Bad news is the newly installed odyssey ODS-AGM16L battery was installed backwards. When the Master switch toggle on the side C/B panel was placed "ON", the wire and a portion of the insulation from the Master relay center post to the master switch overheated and insulation melted in a section of this wire. No start was attempted. Placed the master switch "off". I replaced the master relay,diode and wire to master switch. Then selecting electrical power to the circuit with the master switch toggle "on", all airplane systems were powered and worked normally. Selecting the ACS A-510-2K key switch to "START", THE "INSTRUMENT" 10 A C/B popped. Master switch placed "off".
So far I have replaced: Master relay,diode, center post wire to master switch, (two post) starter relay (internally grounded) and diode. Also have checked voltage and continuity to selected switches, wires, etc.
This 2012 RV8-A came from the builder(now deceased) with many manuals but no builder electric diagrams. I have Van's OP-10,-11 in the manual to look at. The airplane has about 385 hrs total time.
Electric equipment: SKY-TEC FLYWEIGHT 149-12LS starter, PLANE POWER AL-12-E 16013 alternator 60 Amp, Dynon Flight Deck D 180,txp and VFR radio.
Issue not resolved!
 
ACS "START" POSITION POPS c/b "INSTRUMENT"

the van's OP-10 SHOWS A c/b panel labeled "INSTRUMENTS" the only wire from this c/b goes to the BAT terminal on the ACS key switch. I have already bypassed several wires, checking for volts and continuity. The ACS key switch was also rebuilt per SB92-01.
The key switch worked flawlessly since the original build 2012.
got to be a short somewhere? all wires are labeled but very difficult to get to with out removing the instrument panel.
 
Reverse polarity should not damage contactors unless they have have internal diodes.
Does the fuse still blow when all avionics (EFIS, Transponder, Radio) are disconnected?
Each electrical load should have its own fuse. Putting two or more loads on one fuse is poor design.
Inserting an inline fuse in series with the wire that goes between the battery contactor and
master switch could prevent future damage to avionics from reverse battery polarity.
 
It’s one of those problems that there just isn’t enough information available to be objective. The owner doesn’t know how the plane is actually wired so everything is speculation. The systems aren’t designed with reverse polarity protection.

It should have caused an overcurrent of the alternator circuit as well.

It might be worth changing the title of the post to “what happens if you connect your battery backwards”
 
ACS A-510-2K key switch

Next step would be to:
- remove positive power wire from the C/B to the ACS starter switch.
- remove the wire going from the ACS starter switch to the starter solenoid.
Connect both these wires to a temporary separate switch, replacing the function of the ACS starter switch.
If the 10A C/B does not blow, then you know that the ACS switch is damaged.

Good luck
 
Next step would be to:
- remove positive power wire from the C/B to the ACS starter switch.
- remove the wire going from the ACS starter switch to the starter solenoid.
Connect both these wires to a temporary separate switch, replacing the function of the ACS starter switch.
If the 10A C/B does not blow, then you know that the ACS switch is damaged.

Good luck

+1 what Avanza said. Isolate the problem.
 
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