Relatively new to hardwired installs, I have done three or four so far. My problem: I installed a Digitrax DH123 in a P2K Alco S2. The motor functions well. I can change the normal direction of travel by writing different values to CV29. However, I only installed a front LED headlight in this unit. No matter what I have tried so far (CV33, 34, 35, CV61) I cannot make the headlight light when the engine is travelling in the direction the light is shining. I have F0F and F0R both set as non-directional, but the light will only light when the engine is travelling away from it. This is true for any value of CV29. Suggestions of what to try next would be welcome!
Solder both the white and yellow wires to the light. Doing so won’t hurt the decoder and the light will be on in both directions unless you turn off F0.
Not sure what’s going on. I did what you suggested Martin, and nothing changed. This should be so simple to get right, but I’m at a loss. Ready to tear the whole install out again and start over.
Thanks for the suggestion, it was a good one and should have worked.
I am not sure about a DH123, but on my TCS decoders, the blue and white wires power the front headlight; also, if you want front direction only to turn on the light (full, no dimming in reverse), set FOF (CV49 on the TCS) to “0”.
I had a headlight problem when I installed Digitrax decoders in several Kato N scale RDC’s. The headlight function was reversed. I reset CV 33 to 0 and 34 to 2.
I don’t think that reversing the orange and gray wires is going to make a difference in the lighting since the OP says that the motor is functioning well, and he has already tried to CV29 fix. The problem seems to be in the lighting function outputs.
Which of the four DH123 decoders is it? DH123D?
The blue wire is common, white is forward, and yellow is rear. So, the white and blue wires should be operative here.
If all is wired correctly, you could try setting CV61 to 1 instead of 0 (default).
This is what the Digitrax decoder manual has to say about CV61.
Program CV61 to a value of 01 and the decoder will map the normal reverse light function output (yellow) to be controlled by the F4 function key. In addition, the normal forward light function output (white) will bcome a non-directional light output that is controlled by F0 (light function) button on the handheld.
If the throttle is set to forward, the headlight comes on, but the loco moves in the opposite direction, the correct fix is the motor polarity by swapping the orange and grey wires as David suggests. If you change NDOT in CV29 it works, but if you forget about that and reset the decoder, you’ll be scratching your head wondering why it runs in reverse.
Also, since this is a Proto S2, did you run a new orange wire to the bottom of the motor and isolate the tab that contacts the frame? If not, you have a very high likelihood of frying the decoder if the loco ever derails, since the whole frame is connected tot he lower motor brush and if a sheel is pushed into it, it will connect track power to the motor output resulting in fried decoder. The Proto and Atlas Alco switchers are NOT plug and play even if they do have an 8 pin socket.
The one thing that I do before ever installing a decoder in a DC loco is to run the loco on a DC-powered track. Among other things, that will tell you if the motor is wired correctly for directional travel.
I think David B has the answer, the wires to the motor are reversed. Because of that, the decoder is sending DC to the motor to make it go “forward”, and also it turns on the forward headlight…but because the wires are reversed, the polarity is reversed, so the motor turns the wrong direction and the engine goes backwards. Fiddling with the CVs might eventually solve it - you’d have to set it so the headlight goes on when the engine is backing up, because when the decoder thinks the engine is backing up is when it’s really going forward due to the wiring error. Othersise, you could hook the front headlight up to the wires for the rear headlight (and vice versa if using both). But, probably easier to fix the wiring error.
It’s not that the wires are connected the wrong way, I’m sure he connected orange to orang and grey to grey (P2K has color coded wires) - it’s more that LL put the motor in upside-down. Mine are both goofy-wired too, orange to grey and grey to orange, because they run in reverse. Not sure how they goof that up, it’s not like a road switcher that may have run one end forward on one railroad and the other end forward on a different railroad. I have to flip flop all my GP7’s, too. They have them decaled properly witht he little F indications on the end of the frame, but on normal DC they run with that as the rear end, and also on DCC if the colors are all matched.
That Proto S-model issue also applies to the Atlas ones. They look nearly identical inside - probably made by the same factory anyway. Right down to the purple end cap on the motor.
If the motor has been wired in reverse by LL, always a possibility, then the OP is not reporting correctly, because he says that he has already messed with direction on CV29 to no effect.
One way to be sure is to pull out the decoder and run the loco on a DC track. That will tell with certainty the direction of travel as the loco is currently wired.
If the motor direction and headlight direction are out of sync, changing NDOT (the normal direction of travel) will NOT fix that issue. It does just what it says, it changes the ‘normal’ direction of travel, when you tell the loco to travel in forward, it travels in what it considers reverse and turns on the reverse headlight. When you tell the loco to travel in reverse, it travels in what it considers forward and turns on the forward headlight. The purpose of NDOT is for situations such as a loco that is ran short hood forward on most railroads but long hod forward on some. NDOT lets you change which end of the loco is considered forward, but does not change the mapping of the headlights relative to the motor.
Heck, don’t even pull the decoder. Lift the shell and see which way the motor is turning. Gonna have to do that anyhow if you need to flip the two motor wires.
The motor is connected orange-orange and grey-grey. I did do the modifications required to make the loco DCC ready, including milling out the frame below the lower motor brush.
I can get the direction of travel to change, but the headlight direction changes along with it. I will try the CV 33 and 34 combo someone suggested to see if that works. If not, might just pull everything and start from scratch again. It won’t be for a few days, though, since I am waiting for more shrink tube and more time. Especially the latter.
It runs backwards when NDOT is set to forward. I will try swapping the motor leads after I have some more shrink tube on hand and let everyone know the results.