G3X troubleshoot

[Webb]

As I try to finish up avionics install, I ran across these issues and would appreciate any help.

The only error message on the GDU460 was no info from the magnetometer but that is understood since it is not connected. Since it’s a terminal end, there is a 120 ohm resister across the canbus. No heat on that resistor. No issue.

Issue #1 - G5 won’t sync with the GDU460 for Baro although it did on the bench. No error message on the g5 and it is getting ARINC429 data And the GDU 460 is seeing the LRU.

Issue #2 - A 120 ohm resistor across the canbus on the other terminal end which is the roll servo. That resistor is getting really hot. It’s a small resistor and may be too small so it is heating up. Just guessing.

Everything seems to be working except the baros won’t sync between the G5 and the GDU460. And I’m concerned about the resistor heat on the roll servo term end. Neither of these occurred before I did the final install.

I’m wondering if there is a canbus issue going on. The only change is the forward top skin was riveted on which moved some wires around and he GDU460 was removed and reinstalled.

Suggestions?

 

[Richard Connell]

As I try to finish up avionics install, I ran across these issues and would appreciate any help.

The only error message on the GDU460 was no info from the magnetometer but that is understood since it is not connected. Since it’s a terminal end, there is a 120 ohm resister across the canbus. No heat on that resistor. No issue.

Issue #1 - G5 won’t sync with the GDU460 for Baro although it did on the bench. No error message on the g5 and it is getting ARINC429 data And the GDU 460 is seeing the LRU.

Issue #2 - A 120 ohm resistor across the canbus on the other terminal end which is the roll servo. That resistor is getting really hot. It’s a small resistor and may be too small so it is heating up. Just guessing.

Everything seems to be working except the baros won’t sync between the G5 and the GDU460. And I’m concerned about the resistor heat on the roll servo term end. Neither of these occurred before I did the final install.

I’m wondering if there is a canbus issue going on. The only change is the forward top skin was riveted on which moved some wires around and he GDU460 was removed and reinstalled.

Suggestions?

If you are terminating at an GSA28 you should be just jumpering pins 3 and 4. No resistor. It’s in the servo.
If you are terminating at a
GAD 29, GEA 24, GMA 245, GMU 11,
GPS 20A, GSU 25, or G5 you should use a Garmin Can terminator (with a resistor inside it)
Are you wiring in your own loose resistor at the GMU11 end? I guess in theory that’s the same thing as a can terminator plug, but I’ve never seen or heard of anyone doing that.

 

[Webb]

A 120 ohm resistor across the canbus terminal ends simulates the terminal end. Since the wings are not installed, it’s a way to mimic the roll servo and the magnetometer terminal ends Which are in the wings and those are my terminal ends. Worked perfect on the bench.

 

[Richard Connell]

A 120 ohm resistor across the canbus terminal ends simulates the terminal end. Since the wings are not installed, it’s a way to mimic the roll servo and the magnetometer terminal ends Which are in the wings and those are my terminal ends. Worked perfect on the bench.

Ah I see. I read it as everything was installed.
have you verified that you get 60Ω at each can bus node (not ends) and that each LRU is green and that the network error rates are on each are zero?

 

[mburch]

A 120 ohm resistor across the canbus on the other terminal end which is the roll servo. That resistor is getting really hot.

Under normal circumstances there is no appreciable current flowing in the CAN bus wires, so this sounds like you have a short circuit somewhere. If this was my airplane I would not apply power again until I was sure the wiring had been corrected.

 

[Webb]

Under normal circumstances there is no appreciable current flowing in the CAN bus wires, so this sounds like you have a short circuit somewhere. If this was my airplane I would not apply power again until I was sure the wiring had been corrected.

After reading the canbus troubleshooting guide, it sure sounds like it. Looks like I’ve got a date with a volt ohm meter.

 

[Webb]

Update - Went thru the canbus. Found voltage on the Hi side. Fixed. Jumper 120 ohm resistor is now cold on the roll servo terminal end and rest of the CB checks out.

Last issue - G5 has error message not receiving ARINC429. Also G5 won’t sync with GDU 460. It has before. Since the CB checks out from terminal end to terminal end and G5 is in the middle of the CB, only thing I can think of is the CB isn’t connecting in to the G5 and the culprit is the connector.

Looks like another date with Miss Volt Ohm.

 

[Webb]

Update - Miss volt Ohm was ready to party and found a bad connection. Reflowed the solder in the solder sleeve and the G5 is a happy camper.