Checking if Loco has a decoder fitted or not

[Train Mad1707822774]

Hello.

I'm sorry if this has been asked before (I'm sure it has been) but I have looked and can't find anything. I have a couple of Loco's that I've had for a while and I can't remember if they are DCC fitted or not.

I was wondering if it's possible to put them on a programing track to find out, or would that cause damage if the Loco didn't have one. I don't really want to take the body off as I'm worried I might damage the Loco, I have done that before.

Thank you in advance for any help given.

[P-Henny]

"I'm sorry if this has been asked before (I'm sure it has been)....."

Yes it has been.

All suggested tests assume there are no faults present.

There are a number of ways to check for a decoder (read further on), but the simplist & safest way is to use a Multimeter on the Ohms resistance scale.

Take a measurement across the wheels, the wheels with the pickups on them.

If there is no decoder, you should then read the direct resistance of the electric motor coils. I would say something in the 20 to 50 ohm range, maybe as much as 100 ohms but unlikely to be much higher than that.

However, if a decoder is fitted, then you are reading the input resistance of the decoder which will be very much higher in the hundreds or thousands of ohms range if at all.

If you get infinite resistance (an open circuit) then don't assume a decoder is present. The loco wiring or motor may just be faulty. Try the 9 volt battery on wheels test. If no movement of wheels with the battery applied and meter also reads 'open circuit', then it is 'bite the bullet' time to open the loco to investigate further.

Don't have a Multimeter......then get one......they are a crucial tool to have in the toolbox for this hobby or any hobby or DIY task that involves electricity. Very cheap on ebay or the likes of Screwfix or Toolstation.

Alternatively and assuming you have a DC Analogue controller and the loco is both functional and any decoder that might be fitted is configured in CV29 to support DC running. Then if the loco starts to (or trys to) move when the speed knob is turned just a little bit then the loco is likely to be an Analogue loco without a decoder fitted. If the loco only starts to creep when the speed knob is turned say 25% or 30% of its full rotation then the loco is more likely to have a decoder fitted as the decoder needs to see a certain amount of track voltage before it can function.

The Multimeter option is however the more reliable indicator of detecting the presence of a decoder.

Alternatively and assuming you have a DCC layout controller and not a DC Analogue one. Then placing a loco without a decoder fitted on a DCC powered track will make the motor buzz audibly or even take off like a scalded cat. If either event happens, then remove the loco from the track immediately as prolonged connection to DCC track power without a decoder can damage the motor, but a few seconds is all you need to observe this test.

You won't damage anything at all putting a loco on the programming track when no decoder is fitted, but putting it on the live running track without a decoder will (see previous para text). But not being able to read any CVs is not conclusive proof that a decoder is not present, it is only an indicator as there are many reasons why a decoder can not be detected by a controller.

Using the Multimeter is by far the most reliable test to perform.

[Train Mad1707822774]

Hi.

Many thanks for that. I'll get the old multimeter out and do as you said.

Thanks again much obliged.

[ntpntpntp]

It is safe to put the loco on a DCC programming track and attempt to read it, as this only activates the track for brief pulses and listens for acknowledgements. The programming track limits the current allowed.

If there is a decoder the programming software or system should read it. If not then typically you get a "no decoder present" response.

[Train Mad1707822774]

I've tried both methods on four Loco's and found that one had a decoder fitted. I am very grateful for the help given by both of you.

I'm sorry for the late reply but I've been diagnosed as having Carpal tunnel syndrome and one of the things I was told to avoid by my doctor was typing.

I had done some searching of the forum beforehand but couldn't find anything relating to this no matter what I typed in. Thanks again I wouldn't have had a clue without your help.