CDI not responding to GPS signal

[problematique]

I need to figure out the first place to start here.
I have a KLN 94 mounted in a 2000 Cessna 172. I'm not sure when this problem started but I have had some work done behind the panel so I'm hoping something just didn't get reconnected.

When I enter a GPS course and push the GPS/NAV button to specify GPS, the course deviation indicator doesn't move from center no matter where I am in relation to the GPS course. (Thus inhibiting the autopilot to capture the GPS course.) I've tried to troubleshoot and noted that the CDI does perform properly while in NAV mode and following Radials. When it's switched to GPS nothing happens. It does not respond to NAV frequencies while in GPS mode and it does not respond to the GPS course. Any thoughts?

 

[ChemGuy]

take it back to where they broke and ask them to fix it?
if someone was in the panel and now the CSI doesn't get signal from the god, they did something.

good luck getting them to admit it and fix it.

 

[problematique]

take it back to where they broke and ask them to fix it?
if someone was in the panel and now the CSI doesn't get signal from the god, they did something.

good luck getting them to admit it and fix it.

Interestingly (luckily?) my mechanic is excellent with any type of labor issues. I just want a little information before I drop off the plane. Like- is this something that could have easily been "unplugged" (or whatever has to happen) when working behind the panel. OR is it relatively difficult to get this type of result. OR is this a part of the system that could singularly fail even though the NAV portion works properly. Is it more likely that its a problem with the GPS unit or the CDI unit? I just basically want to know whats involved with the signal that is received by the CDI.
Has anyone had this particular issue?

 

[bradg33]

Interestingly (luckily?) my mechanic is excellent with any type of labor issues. I just want a little information before I drop off the plane. Like- is this something that could have easily been "unplugged" (or whatever has to happen) when working behind the panel. OR is it relatively difficult to get this type of result. OR is this a part of the system that could singularly fail even though the NAV portion works properly. Is it more likely that its a problem with the GPS unit or the CDI unit? I just basically want to know whats involved with the signal that is received by the CDI.
Has anyone had this particular issue?

There's no one size fits all answer to this question. Avionics installations are largely "custom," so it's hard for us to know exactly how your system is wired. More than likely, a plug got disconnected or a wire was pulled out of a connector. If it were me, I'd start by checking the harness from the GPS to your annunciator/switch box. Then I'd check the connections from that switch box to the CDI. If the CDI is responding to NAV input, the issue may be between the GPS and the annuncaiator/switch, as the General left/right signals are getting from the switch to the CDI

 

[problematique]

There's no one size fits all answer to this question. Avionics installations are largely "custom," so it's hard for us to know exactly how your system is wired. More than likely, a plug got disconnected or a wire was pulled out of a connector. If it were me, I'd start by checking the harness from the GPS to your annunciator/switch box. Then I'd check the connections from that switch box to the CDI. If the CDI is responding to NAV input, the issue may be between the GPS and the annuncaiator/switch, as the General left/right signals are getting from the switch to the CDI

Perfect,
thanks for the info.

 

[hotprops]

bad connection at isdo switch

 

[coloradobluesky]

It's wired wrong or has a bad connection is most likely. You need the manual for it and the manual for the avionics its connected to. Not something most mechanics or owners can do. Find and avionics shop and hire them to fix it.