I recently had my RV12iS (iS engine, dual G3X, TT 104 hours) painted. On my initial preflight and engine run up for my trip home from the paint shop the Lane A and B switches and associated lights functioned normally. The flight was uneventful, and the engine appeared to be running reasonably smoothly, with minimal vibration. However, on my next preflight I noticed the Lane A light never illuminated, regardless of Lane A and B switch positions. The function of the Lane A switch itself appeared normal, with expected drop out of engine instruments, and normal running of the engine when Lane B was turned off. Lane B switch and light behaved normally with expected drop out of engine instruments.  

ECU faults were noted in the Engine Information page only when either switch was off, but with both on, no faults were noted. I concluded the problem was with the indicator light.

Investigation included:

  • Removal and inspection of the ignition switch module.
  • Inspection of the wire harness d-sub pins at both ends of the cable connecting the ignition module to the HIC connector module. Special attention was given to the wires associated with the indicator light per the schematic diagram.
  • Wiggling all connectors on the HIC module to see if the Lane A light would briefly come on.

No abnormalities were found up to this point.

I next pulled the cowl cover and inspected the Rotax engine fusebox. While I could not find documentation as to specifically how the indicator light is wired through the fuse box (or what each fuse in the fusebox is for), I did notice a 2 AMP fuse was blown. I replaced the fuse, and the Lane A indicator light now functions normally. I have cycled the avionics on and off, as well as started the engine numerous times since, and Lane A light continues to function normally. With both Lane A and B switches “on”, there are no ECU faults.  

I also performed a dynamic prop balance post painting, Prior to painting the IPS was 0.04. Post painting it was 0.14 with improvement to 0.02 IPS post balancing. The minimal vibration I noticed previously is improved post balancing.

My questions:

  • Although the light and Lane switches appear to be working normally now, should I be looking elsewhere for a cause of the blown fuse?
  • It seems coincidental that the problem occurred after painting. Could this be vibration related?
  • Can anyone point me to a description of what circuit each fuse in the fusebox protects?

Question also posted on VAF and submitted to Van's technical support



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