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CanBus Query

design4p

Active Member
Hi,

I am having difficulty with my CanBus connections so I have only connected 2 LRU's with cable - Garmin GAD 27 and Garmin GEA24. Cable is between the 2 LRU's and cable out of each with no onward connections.

Note: Both LRU's are connected to their respective hardware (sensors, lights, flaps, trims etc)

Here is the query:

With both connectors out of the LRU's (not plugged in) all OK ie continuity independently along the HI and along the LO and along the shield. No cross continuity.

However, if I plug the related connector into either of the LRU's I get a resistance reading between the HI and the LO of 49 kilo ohms. (49,000 ohms).

Does this reading of such a high resistance mean NO continuity between HI and LO? and therefore the wiring is OK???

John (CanBus Confused)
 
your getting a reading through the circuits connected to the can bus inside the LRU.

bob burns
RV-4 N82RB
 
CanBus

I installed the G5 and GMU-11 in my -8 recently and had no communication between the two units. After several hrs of troubleshooting with no success, I decided to recrimp the canbus pins and shield ground. Started at the GMU-11 connector because it was easiest to get to. I cut and installed new pins, and re-soldered a new shield ground. Decided to op check before moving on to the G5 and system worked like it was supposed to.
 
CAN bus termination

Hi,

I am having difficulty with my CanBus connections so I have only connected 2 LRU's with cable - Garmin GAD 27 and Garmin GEA24. Cable is between the 2 LRU's and cable out of each with no onward connections.

Note: Both LRU's are connected to their respective hardware (sensors, lights, flaps, trims etc)

Here is the query:

With both connectors out of the LRU's (not plugged in) all OK ie continuity independently along the HI and along the LO and along the shield. No cross continuity.

However, if I plug the related connector into either of the LRU's I get a resistance reading between the HI and the LO of 49 kilo ohms. (49,000 ohms).

Does this reading of such a high resistance mean NO continuity between HI and LO? and therefore the wiring is OK???

John (CanBus Confused)

John,

When it is all said and done, you will have 2-120 ohm resistors in parallel across the bus. If you measure resistance at any intermediate LRU, across CAN hi and CAN lo, you should read 60 ohms. If you read 120, you only have 1 termination, if you read less than 60, you likely have too many terminations.

Please feel free to send any questions to us directly at [email protected]

Thanks,

Justin
 
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