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Troubleshooting Intermittant Mode C
I'm having issues with the mode C on my 180. What is happening is that mode A is working fine, but altitude is working intermittently. I took the plane in for its annual, which included the static pitot check. Everything was working fine prior to the annual, and the static pitot check was completed with no issues. Upon flying home the controller called me and said that the altitude was intermittent. We have tried a new encoder, new antenna, and tried a loaner transponder with the new encoder. The wiring harness between the transponder and the encoder was also checked and is wired properly. We have been troubleshooting this over the last month, but the problem is escaping us so far. For example today we installed a new antenna because the mode c was found to cut out if we tapped beside the antenna. We tested the system thoroughly on the ground and it was working perfect. As soon as I was airborne, the altitude was cutting in and out. Any ideas on what could be happening, and what to try next would be very welcome. My transponder is a Narco AT 150.
Thanks
Larry
- Larry Biever
- ICS member
- Posts: 33
- Joined: Wed Dec 03, 2008 3:20 pm
- Location: Airdrie Alberta Canada
JIMICS2452- ICS member
- Posts: 254
- Joined: Sat Mar 09, 2002 9:26 pm
- Location: Pine Shadows Airpark - North Fort Myers, FL
Re: Troubleshooting Intermittant Mode C
Not yet. Mark was thinking this would be next.
- Larry Biever
- ICS member
- Posts: 33
- Joined: Wed Dec 03, 2008 3:20 pm
- Location: Airdrie Alberta Canada
Re: Troubleshooting Intermittant Mode C
JIMICS2452- ICS member
- Posts: 254
- Joined: Sat Mar 09, 2002 9:26 pm
- Location: Pine Shadows Airpark - North Fort Myers, FL
Re: Troubleshooting Intermittant Mode C
- Larry Biever
- ICS member
- Posts: 33
- Joined: Wed Dec 03, 2008 3:20 pm
- Location: Airdrie Alberta Canada
Re: Troubleshooting Intermittant Mode C
- Larry Biever
- ICS member
- Posts: 33
- Joined: Wed Dec 03, 2008 3:20 pm
- Location: Airdrie Alberta Canada
Re: Troubleshooting Intermittant Mode C
Thanks,
-Quint
- Quint Van Deman
- Posts: 93
- Joined: Sun Feb 13, 2011 5:14 pm
Re: Troubleshooting Intermittant Mode C
The plane will check fine on the ground, because the test equipment is close to the airplane and They're checking for signal function, not for power out. the Transponder will check out great on the bench because their test rig has a new good coax.
If the coax is over ten years old, replace it all.
FCC lic'd Cellular radio tech for 25 years.
Pat Elliott- Posts: 39
- Joined: Sat Jul 05, 2014 4:17 am
- Location: Coos Bay
Re: Troubleshooting Intermittant Mode C
- Ron B Keil
- ICS Secretary
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- Joined: Sat Mar 06, 2010 2:10 am