new garmin gtn750 installed in 260C comanche

[Edward Pencosky]

I had a Garmin 750 installed last month and I am getting a intermitting glide slope flag. I removed the antenna on top of tail and cleaned the connections and still happens. I noticed the cable comes up thru tail, to antenna and makes a u turn and goes back. It does not look like the center lead in cable is being used.To me it looks like they use the shield wire at 2 places and they go to the 2 connections on antenna,am I right that the center lead isnt used???? another question is how hard is it to replace wire to a new one? do side panels come out or can i get to them thru belly or floor? not sure if i can do some test on cable as I hate to change it for nothing. Im going to radio installer this weekend for testing.If cable is bad I guess its not his fault but dont want to change it for nothing

[md11flyer]

Edward, not 100% sure of what is happening with your cable to antenae connection, but if that antennae worked with your old glide slope without problems then
my guess would be a wire from your new Gamin to the indicator is causing the problem. I would take it back to the avionics shop and have them confirm the problem.
Its always difficult with intermittent faults, but in this case if its a bad solder connection (wire to pin) then just wiggleling the bundle should duplicate the intermittant flag.
Another check would be to see if you get the flag not only in vLoc mode but do you get it when flying a GPS approach using the LNAV/VNAV on the unit. IF you get the intermittant GS flag
when shooting the GPS approach then you know its nothing to do with the GS antennae /cable.
I had an intermittant GS flag in my KNI 520 indicator as well when I had A new Garmin 430W installed. It turned out to be a solder joint in the connector, which the shop fixed with apologies. These problems can happen when resoldering new wires into old connectors....even the best of shops can have this happen to them.

Good Luck,
Gary

[Edward Pencosky]

Gary no i dont get a flag when flying the gps approach. I also got no GPS indication on screen and it lasted 30 seconds. I will bring plane to avionics shop as they need to fix it. I spoke to them today and they want me to see if I loose flag on both radios at same time.Also they said to push radio in tray when this happens.Time will tell I guess....

[VANBLADEREN]

One other thing to consider is that the radio shop may have used a NAV-NAV1-NAV2-GS splitter and fed the 750 with the nav signal and a second radio(kx 155 with a GS), so NAV and GS to that radio. The 750 must be fed with a splitter that does not pull out the GS as it has an internal splitter. So you need a NAV-NAV1 NAV2 splitter. NAV 2 then goes to the old splitter which feeds the KX 155.

If you have a good nav signal, then the cable is probably ok.

Something else to consider.

Regards

jvb

[Edward Pencosky]

thanks for your respond john.I spoke to garmin teck and he did mention that 750 needs a special splitter.The shop said they put than in but must double check that.Garmin is sending a loaner to first check its not the radio.Lets hope I can get this solved as its something no one needs after spending big bucks.. I am using my old collins head as the glide slope indicator as im told is ok ????