GNS430W incorrect OBS input?

cowman

cowman

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Just got this airplane, didn't notice this in CDI mode but quickly found it in VLOC when we tried tuning in a VOR.

In the diag screen the OBS is erratic, seems like there's almost a dead zone.

Tried going through a calibration screen where you set it to 150... 150 reads ok but again it barely reaponds when being turned. Readings are always off and often don't change while turning the knob.

Anyone got any ideas/suggestions?
 
That's a pretty sketchy description, there's no such thing as "CDI mode" in the 430, and I have no idea what the "diag screen" is. One would need a lot more info to even begin to guess what's going on.
 
I'll hazard a guess.....

1) Don't know about this diagnostic screen you speak of... photo please?

2) Are you tuning a VOR frequency on the Nav radio, but not switching the CDI from GPS mode to VOR mode?

That's a blonde moment I've done a few times. Planned to fly a radial, got set up to intercept it, tuned and identified the frequency correctly, twisted the OBS on NAV1 to the radial I wanted... and then waited for the needle to move...

Nothing.

Fiddled with the OBS knob again

Nothing

Muttered a curse and gave a "what's going on?" look to the instructor in the right seat. Who then proceeded to laugh at me, reach over to the GNS and press the CDI button.

Instantly the annuciator on the CDI switched from GPS to VLOC, the needle moved, and I did the V8 slap to my forehead.
 
Yeah my apologies for my hash of terminology.


This may be clearer. Note where the OBS is set to and what the 430 says its set to. This is in a nutshell the problem. Talked to an avionics guy about, he suspects the actual OBS
 

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Most likely it is a connection problem. There are 6 wires between the G430 and the CDI for the OBS function. Try first pulling the G430 out of its tray and spray contact cleaner on all the contacts. Reinstall G430. Do the same with the CDI connector. Check OBS reading again. If the reading still off check for broken wires on P4001 connector pins 31 thru 36 on the G430 tray. It is rare for a CDI to go bad.

José
 
Sounds reasonable. Is this something I can do myself or do I need and A&P or avionics person to sign off on it?
 
Slight thread hi-jack. Would dirty/loose connections be at play when the CDI does NOT display the TO-FROM flag in either GPS or VLOC modes and the G430W displays "VLOC remote transfer switch stuck" message?
 
Piloto said:
Most likely it is a connection problem. There are 6 wires between the G430 and the CDI for the OBS function. Try first pulling the G430 out of its tray and spray contact cleaner on all the contacts. Reinstall G430. Do the same with the CDI connector. Check OBS reading again. If the reading still off check for broken wires on P4001 connector pins 31 thru 36 on the G430 tray. It is rare for a CDI to go bad.

José
Click to expand...

Exactly what I was going to suggest Jose. Also check for bent or pushed in pins on the rack and unit.

I had a bent pin (one of the signal wires) on the rack side cause this exact problem. Last time it was in the avionics shop they bent a pin when they pushed the unit back in, and I didn't notice it for over a year.
 
cowman said:
Sounds reasonable. Is this something I can do myself or do I need and A&P or avionics person to sign off on it?
Click to expand...

This is a minor fix that you can do it yourself if you are handy with tools. To pull the 430 you will need a long hex tool to rotate the latching cam and then grab the unit on the side (not by the knobs) to pull it out. To seat it back is a little bit tricky. If not try to get the local avionics guy to give you a hand. I hope is not a bent pin like John mention. It is a PIA replacing those pins.

Contacts oxidation is a common event on anything that has connectors. The symptom is usually intermittent operation. About 60% of the avionics intermittent problems are due to contact oxidation that can be fixed with contact cleaner. Whenever experiencing an avionics problem try cleaning the contacts first before spending any money. You will save a lot

José
 
AggieMike88 said:
I'll hazard a guess.....

1) Don't know about this diagnostic screen you speak of... photo please?

2) Are you tuning a VOR frequency on the Nav radio, but not switching the CDI from GPS mode to VOR mode?

That's a blonde moment I've done a few times. Planned to fly a radial, got set up to intercept it, tuned and identified the frequency correctly, twisted the OBS on NAV1 to the radial I wanted... and then waited for the needle to move...

Nothing.

Fiddled with the OBS knob again

Nothing

Muttered a curse and gave a "what's going on?" look to the instructor in the right seat. Who then proceeded to laugh at me, reach over to the GNS and press the CDI button.

Instantly the annuciator on the CDI switched from GPS to VLOC, the needle moved, and I did the V8 slap to my forehead.
Click to expand...

Sounds like you fly with my CFII. :D
 
Make sure the GNS is fully seated in the tray. There is a procedure in the install manual to verify acceptable tray / pin engagement. It's possible for the panel to prevent the unit from fully engaging into the tray...installation error or hopefully just needs to be seated a bit more.

Tim
 
FYI in case anyone else has an issue.

It was the indicator. Garmin is going to repair for $180 and send it back.
 
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