Lane A/B Lights & Status

The first thing I would do is look at the battery. How old is it? I saw erratic behavior of my Lane Lights with the original battery. I replaced it with an Odyssey brand battery. It is a stronger and more durable battery. The problems all went away. 

Thanks Scott. Will do. 

Drew,

It sounds like you are not getting start power.  Is the start power on the Sling 2 manually controlled with a switch or is it an automatic function through a relay? Maybe you could post the Sling 2 wiring diagram section relevant to this function.   

I am perplexed because power from the master switch powers the #3 in fuse box and the #1 (#2 fuse box) & #2 (Reg A) relays. This is where I get the relay clicks and no lighting of Lane warning light  

If I turn on the ECU backup the engine turns over every time. The ECU Backup also provides direct power to the Fuse box and Reg A, by design, and Lane warning light properly function.

I did notice that my battery CCA was less than Rotax recommended 350 amp.  I ordered a new battery.  Not sure if new battery will make difference, but at least I will be above Rotax recommended minimum. 

Thanks for your help. 

Drew,

The Rotax typical wiring diagram shows a two pole manual switch for start power, which is the same function as your relays 1 and 2. Relay 1 closes 12+ power to the 2 terminal of the X3 connector, and relay 2 connects the airframe ground to the isolated Rotax ground.  In the case of your aircraft, relays 1 and 2 are only engaged when you have the key in the start position.  Relay 3 closes at the same time, which energizes the starter.  There is a note on the wiring diagram that either indicates that each of these relays is a 4-pole relay with only 1 pole used, or that all three of these relays are actually part of a single 4-pole relay… probably the former so I’ll refer to them as separate relays.

The reason that the start power is typically a separate (manual) switch is so that it can be turned on prior to starting, in order to run the fuel pumps and check/clear the lanes.  It also allows for the switch to remain on until the engine has started and stabilized, at which time the alternator(s) are providing reliable power to the engine.  The way your aircraft is wired you don’t get “start power” until the moment you turn the key to the start position, and “start power” is turned off the moment the key released from the start position. I would think that this would provide unreliable starting unless the backup power switch is also used.  But, using the backup power switch for normal starting defeats the intended function of the “start power” switch.  I’m curious if the standard procedure for starting your aircraft includes using the backup power switch to prime the pumps, clear the lanes and is then left on until the engine is running?

With start power being provided by a relay, I could see a low battery situation causing the relay to drop out on low voltage when the starter is engaged.  You could try replacing relays 1 and 2.  But even so, I personally don’t like the starting circuit.  If it was my aircraft, I would install a 2-pole toggle switch for start power (relay 1,2), and then connect the starter relay (relay  3) directly to the starter key switch. This would eliminate the relay(s) altogether.   With this done, you would follow the starting procedure in the Rotax 912iS operating manual.  Of course if the aircraft is an SLSA, you would need a Letter of Authorization from the manufacturer to make these changes