Bachmann Class 105 DMU DCC Problems

[mmmbeeer]

Has anyone come across this - Bachmann 31-326A Class 105 DMU trailer car does work with DCC?

I recently bought this model and ran it in on DC and all was fine. I then installed two Hornby R8249 decoders and on a programming track set them to address 8, one at a time. The motor car work fine, lights and all, but the trailer car lights did not work. I tried reading back the address of the trailer car on the programming track but it wouldn't read. I swapped the decoders around, the one moved into the motor car was still set to address 3, so I set it to 8 and the motor car was fine. The trailer car lights would still not worked with the decoder originally in the motor car. So I swapped them back, same result. I set the trailer back to DC working and lights worked fine. So the trailer went back to the shop and a new one delivered 4 days later.

On testing, exactly the same thing happened again. Next to the socket there is an 8 and 4 printed so I assume the decoder was in the correct way round. Every time the plug was inserted I check with a magnifying glass that the pins were lined up OK. I recently installed Hornby R8249s into the Bachmann class 108 DMU without any issues, so I don't think it's me being dumb (yet???). I use the Hornby Elite DCC controller, before anyone asks.

Anyone got any ideas, I've run out? Excpet to send it back again.

[D0260]

Don't think the R8249 will program or read from a DCC controller unless there is a 'load' .... In the power car , the load is the motor, so it works fine. I think you need to add a 100ohm resistor across the dummy car decoder orange and grey -motor- wires..

Its one of the quirks and differences between Motor decoders ( normall DCC decoders) and 'function' decoders that do not need a load , but use different address'es..

[Essex2Visuvesi]

Is that one of the ones were you need to program it in the motor car, set it to reverse and then swap it back into the dummy?

[mmmbeeer]

The R8249 decoder worked fine in the class 108 dmu trailer car, so I'm not sure about that. I could give it a try.....

[dubdee1000]

D0260 and E2V have stolen the wind from my sails - its a programming thing with trailer cars. Some trailers seem to take the programming better than others. As has been said, i'd do the programming in a motorised unit, taking care to ensure that i'd reversed the direction of travel (otherwise you'll get headlamps on at both ends at the same time), then put that decoder into the unpowered trailer. You get the same problem with Bachmann decoders on occasions, so i'm sure what you've got will be fine

[mmmbeeer]

D0260 and E2V have stolen the wind from my sails - its a programming thing with trailer cars. Some trailers seem to take the programming better than others. As has been said, i'd do the programming in a motorised unit, taking care to ensure that i'd reversed the direction of travel (otherwise you'll get headlamps on at both ends at the same time), then put that decoder into the unpowered trailer. You get the same problem with Bachmann decoders on occasions, so i'm sure what you've got will be fine

I took the one from the powered car and put it in the trailer but it didn't work, but I didn't reverse it, still no lights though.

[dubdee1000]

ok, that the 105 works ok on DC suggests that there isn't a major problem with it.

Lets try starting completely afresh. Long winded, but it'll show up where the fault is. Forgive me if you've already done this, but starting from first principles helps me follow it

Use your elite to reset both decoders. To do this, you'll have to put each one (lets call them A & B) into the power car, onto the programming track and do the reset. So, this is not just changing the loco address, but a reset of the chip itself. It should go back to the address of 3

After each reset, try the power car alone on your main track for movement and check its lights.

So to recap, chip A into the power car, onto the programming track, do a reset, then test it on the main. Then repeat for chip B

If all is well, then we can move on. From what you've written so far, i guess it should be. If the power car doesn't behave as it should, then you have a problem with a decoder. As you'll have done a reset, any minor programming issue should have been cleared and a persistence of the fault would suggest that there is a more serious fault with the chip.

Can you try this first and we'll see what happens. We'll get to the bottom of this eventually!

[mmmbeeer]

ok, that the 105 works ok on DC suggests that there isn't a major problem with it.

Lets try starting completely afresh. Long winded, but it'll show up where the fault is. Forgive me if you've already done this, but starting from first principles helps me follow it

Use your elite to reset both decoders. To do this, you'll have to put each one (lets call them A & B) into the power car, onto the programming track and do the reset. So, this is not just changing the loco address, but a reset of the chip itself. It should go back to the address of 3

After each reset, try the power car alone on your main track for movement and check its lights.

So to recap, chip A into the power car, onto the programming track, do a reset, then test it on the main. Then repeat for chip B

If all is well, then we can move on. From what you've written so far, i guess it should be. If the power car doesn't behave as it should, then you have a problem with a decoder. As you'll have done a reset, any minor programming issue should have been cleared and a persistence of the fault would suggest that there is a more serious fault with the chip.

Can you try this first and we'll see what happens. We'll get to the bottom of this eventually!

Both decoders work fine in the power car so I don't see the point of a reset. The trailer car has gone back again to the shop, so I'll have to wait until another one comes back, although I suspect it'll be the same. The website I got it from recommended the Hornby decoder for this model but I have my doubts. I'll keep you all informed.....