No bus devices

[Follybob]

Guys,

After experiencing intermittent sims gauge failure I order a new t connector and went one by one using the new blue tee to find the bad one. I could not get the gauges to read the engine port or starboard. If I ask it to list bus devices it says no devices on bus. Can someone please help me? I am at my wit's end.

[Moonlighter]

If you have tested all T pieces and they are OK, then likley culprit is an engine interface cable failure. Or a least a wiring break in the interface cable connectors. So check them carefully and make sure that where the wires enter the back of plugs they are all good. Also check the adapter cable plugs and wiring itself for breaks and corrosion.

If they are all good, the interface cable itself may have failed.

You havent stated your network setup - is it a single engine setup or twins? The above comment assumes single engine.

Note: if the cable itself has failed, and ypu need a new one, you will need to be careful to get the right cable. You mentioned "blue" T pieces and this keads me to believe you have quite an old setup??

Can you confirm the engine year and that your network is using the old Lowrance (large) blue T pieces? We can then recommend a version of the cable to suit if you need to get a new one.

[Follybob]

They are the blue ones. Motors are twin df225s. The weird thing is nothing else shows up on the bus and the gps and other items are connected to it .worked fine for 2 years then ontermiteenet then nothing.

[Moonlighter]

1. What GPS do you have connected to the network? Assuming its not just a GPS puck antenna, haveyou been into its network device list to see what is showing up?

2. What year are the engines? Important info!!

3. The blue T's are notorious for failing due mainly to corrosion. Are you certain they are good?

4. If the SMIs gauges are lighting up, then the bus must have power. So the problem can only be

- a wire broken somewhere - did you check wiring as suggested in my previous post??

- a failed T piece, probbaly th eone that the interface is connected to. Swap the interface cable onto to the SMIS's T piece and see what happens. If the SMIs doesnt light up, ghere is your culprit.

- a failed interface cable. Does happen, and yours is quite old......

[2014DF25ARS]

It sounds as though you have ALL your devices (engines, GPS, whatever) connected to the network. Like a radio channel, the communication protocol on the network requires that all the devices cooperate with some rules and allow each other to talk. A failure in ANY of those devices can potentially trash ALL communications on the network and make it impossible for ANY device to communicate. Think of a radio channel where one person holds their TRANSMIT button and prevents anyone else from talking... If you haven't already done it, I suggest you start by unplugging everything but the SMIS gauge from your network, then plug in each device one at a time with the gauge. I suspect that you will find when you plug in one of the devices, all the devices will disappear from the network.

[Follybob]

I think the motors are 2007s. 2 lmf400 gauges that both light up and both say no bus devices. Simrad nss evo also on bus. Motors have separate cables coming to the bus which is mounted under the console and screwed solidly into the console. The gps doesn't see the network either. Should I switch to different cables? How hard would that be to do?

[Moonlighter]

So, we now know youve got twin engines, and no bus devices showing on either the SMIS displays or on the NSS.

Pls confirm that the SMIS displays arent showing on the NSS device list, and vice versa??

If so, it points to a fault in the network wiring/hardware, a bad T piece, or, as 2014 DF said, one of those devices may be bad shutting the network down. Do as he said - unplug one device at a time, including the interfaces, test each time and see what happens.

It seems unlikely that both interface cables have failed at the same time unless something else has happened recently to the boat's system? Like a big electrical spike of some kind?

Last suggestion- please double check the network power supply, including its fuse - please remove the fuse/power connections, clean, confirm good, and refit.

[Follybob]

Success!! Thank you so much for your help! The key piece of information that I was missing is that any one device on the bus can take the whole thing down. Rearranged the tees so I only had power, one gauge, and one motor. It was able to see that motor. Switched motor cables over at the tee and could not see that motor. Was therefore able to determine the problem was the starboard motor. Attached its interface cable to the port motor backbone cable at the motor and it was able to see the motor so I knew I had a bad cable . Replaced it and I am back up and running. Thank you thank you thank you! FYI the starboard rigging tube was full of water and penetrated the cable.

[Moonlighter]

Good you figured it out.

The new cable you got - which version? Need to be careful with software versions as some may not work properly with earlier motors like yours - but if fuel flow from new cable looks good (same as other motor) you will be Ok, so thats the key thing to check. If its miles different then will need to change software.