Question on the Circuit for the Nav Running Lights
Hi all,
Yesterday while on the second leg of a training/fuel run I noticed that my alternator gauge was showing an output of only 15, where in a normal configuration it shows about 20. ('76 Warrior, by the way.) I cycled the alternator and turned on/off the pitot heat, and it went up and down in response as you would expect. So I just flew home watching it.
While in the air it occurred to me that likely something which normally draws power was not doing so at the moment. All the circuit breakers were in, and the avionics were fine, so the only other thing I have on normally are the running lights.
Sure enough, went I got back home I checked and the red and green lights on the wings, and white light on the tail, were not coming on. The red beacon on the tail, which is on the same switch, was working fine. And yes, I tested the nav dimmer to make sure I hadn't accidentally turned it off.
So I've already called my A/P, but if anyone here can think of an obvious break in that circuit that we should check I'd appreciate it. Thanks!
Re: Question on the Circuit for the Nav Running Lights
Hi Jeff. Been there, done that. Twice. Let's hope it's only the breaker. Otherwise, it's probably the switch itself or connector L1 located immediately behind the dimmer assembly (attached to the dimmer assembly, accessible behind the panel). I can email a .pdf of the wiring if needed.
In summary, +12v is routed to the Nav lights via 7.5A breaker, then via connector L1 pin A, the rotary switch on the dimmer subassy, L1 pin B, L1 pin pin J to terminal 11 on the buss strip.
First nav light failure was due to avionics shop neglecting to fully insert L1 following a GPS installion. Took 30 min to figure it out, 30 seconds to fix.
Last year, the switch inside the rotary dimmer failed in the open position. Major pain to replace. Have to remove instruments at bottom of avionics stack for access to screws holding dimmer subassy to the panel. Took 30 minutes to troubleshoot, 3hrs to replace.
Re: Question on the Circuit for the Nav Running Lights
Tom, thanks for that. I'll take a look in my service manual documentation. Also, funny you should mention that one time was caused by the avionics shop after installing a GPS. I just had a Garmin 430W installed a few months ago so that could very well be it.
Re: Question on the Circuit for the Nav Running Lights
Tom, if you're still checking this, can you send me that PDF of the wiring diagram? What had been an intermittent problem now seems to be a permanent one, as the Nav lights will not come on at all. I suspect a bad breaker but will also check the L1 connectors as you suggest.
Re: Question on the Circuit for the Nav Running Lights
Hey all,
I want to re-open this inquiry to provide latest details and see if there are any other thoughts. Having checked the L1 wiring connection, the circuit breaker, even tightening the wires at the junction box under the seat, I'm still having intermittent problems with the nav lights.
Intermittent is the key word. Of course, whenever my A/P looks at it, they're working. But often when I'm doing pre-flight the nav lights just won't come on. Interestingly, they always do seem to come on once everything is fired up and things seems to "warm up" a little bit.
I don't know if "warming up" has anything to do with this, but that's just my way of saying that after the plane has been operating for awhile they seem to work. And sometimes, they do work on pre-flight as well. Very vexing.
Could this be indicative of a switch going bad? Maybe some intermittent shorting or rubbing of wires inside the plane? Anybody else have ideas?
The plane is going in for annual on May 19th so we're definitely going to troubleshoot this some more, but if anyone can point me to likely causes that will be helpful. Thanks!
