400W install--no see antenna
 

Hi guys,
I am installing a used 400W in my buddies RV-6 with a new 345 and G5.
I have powered it up and it runs through it's test cycle and offers up a message.
"GPS is not responding Check GPS antenna"
Well I installed a new GA35 antenna which is the recommended one and ran new RG400 with proper BNC and TNC connections. All looks good and checked and rechecked but no joy.
Any thoughts before I reach out to Stein or Garmin or a local shop to check the units??????
Tia.

GPS - no antenna
 

In that case I?ll ask an obvious question- are the connector centre pins fully out in place? I?ve seen them accidentally retracted & by paid ?professionals? ;)

GPS antenna
 

I only ask because I could see myself doing this... after making the changes to the antenna, are you moving out of the hangar to perform the test where the antenna could actually see the satellites?

Thanks for replys....
 

Thanks for your thoughts guys.
Yes the center pin tip of the RG400 cable is flush with the barrel.
Yes we are moving it outside and even flying it!

I have slid unit out of tray and looked at DB connectors and antenna cable slip in connectors all seem fine.
I did the manual's test of slid into tray until it comes on and count the turns to tighten, the book says min of 3 and I had 4.5 so I think it is seated.
I also installed the older non wass antenna and still no connection or no differance in the "message".

Question? This is a "older unit" not too old but we got a "new" 2018 antenna GA35...any chance the 400 software needs an update to "see" the newer antenna? Mod level on rear of unit starts at 8 and goes to 19 with no mods done. So I assume mods 1 through 7 were done at manufacture.
There is a "note" #4 on manual, page 1-10 that says....
"It is anticipated that there will be no operational limitations when using a GA 35 antenna in conjunction with a future version of GPS software. Consequently, it is recommended that the GA 35 antenna be used wherever possible"

I don't know about the 400, but it's cousin, the GNS480 needed a software update to be WAAS compliant for 2020. A local avionics shop had the update cards. Also, the 480 is notorious for having connection problems related to the unit not getting seating well for good connection to the plugs in the tray.

Have a friend with a good 400W installation? You could try swapping units to verify if it's the device or the installation that is the culprit.

Update-found problem
 

I had the 400W and the new antenna checked out at a radio shop and they tested fine. Clearly I had an install problem. Started ohming the connectors, replaced one end, then replaced the other! The second one cleared the problem. From now on, I will be checking continuity as I install BNC connectors.
Thanks for the troubleshooting input!

Hey Bob, sorry for such an ignorant question, but what ohm reading tells you its a bad connection, and what ohm reading tells you its a good connection?

You're not looking for a resistance reading. You're looking for continuity. Direct short between center conductor and pin (0 Ohms) is good. Open circuit (Infinite Ohms) is bad. Direct short between center pin and shield is bad.

Mel is correct
 

What Mel said......Tks Mel.

Clearly I made up the bad connector, The only differance was I crimped the original/bad.....and I soldered the replacement/good. Very hard to take one apart after assembly, so I will never know for sure why it was bad.

Lesson for me is that if I check the connector right after I assemble it I will know right then and fix it......instead of "assuming" it was good and causing lots of troubleshooting.

Thanks again for everyone's input. Still learning!