Thread: Odd G327 Failure

My G327 Transponder has failed in a very strange way. About 10 minutes after turning on, it reports altitudes of FL287 to 290. Since I'm in a Mode B overlay, I'm AOG until I get it fixed, so it went to the local avionics shop.

They first tried swapping the encoder, but the problem persisted. Wiring from the encoder to the transponder tray supposedly checks out Ok. The transponder does not act up on the bench. However, they feel that the transponder is the culprit and they want to send it to Garmin. Flat service fee at Garmin is $650 no matter what's wrong. Since I'm under a Class B, I'm kind of at their mercy.

Has anyone had this kind of failure? Any ideas?

Doug

Hi Doug,

Was it working OK before and then had an acute problem?

Airplane just came out of annual and a G696 install. Wiring could be an issue, but (1) the problem is intermittent and (2) avionics folks checked the wiring and it's Ok. Transponder could have gotten static discharge or something during the annual, unlikely but possible. Problem just showed up, no previous warning signs.

I thought about just installing a new encoder and wiring harness (factory wired them up for gray code instead of RS-232), but that's not really allowed - A&P has to sign off on the Transponder system, and any new parts require a new transponder certification, which I certainly can't do.

I suppose if it does turn out to be the wiring, that will be the last time I use this shop....

Doug

Since it just came from the shop and had new wiring done, My bet would be a wiring issue until proven otherwise. It wasn't an issue until they put in the 696 and now it's a transponder problem. Not my first choice.

Update: Garmin serviced the transponder and this seems to have fixed the problem. It appears that they replaced some of the internals - the display had some of that protective film that comes on new electronics. So far so good, but I'll keep a close eye on it.

Doug