Time to start putting decoders in. I have the HO Spectrum Doodlebug with no directions, I got from a friend. How do I take the shell off and what kind of a decoder will it want. There seems to be a head light and interior lighting, I think.
The body shell is held onto the chassis by clips moulded as part of the glazing - you need to gently pull the sides apart to disengage these. It can be tricky, so take your time. A few strips of thin cardboard might be handy - if you slip these between the glazing and the chassis it will stop the clips re-engaging.
Regarding decoders, I used a Lenz 1014. The headlight needs a resistor as does the interior light, otherwise they get very hot and will probably melt the shell. I can’t remember what value of resistor I fitted, trial and improvement seemed to work (basically I tried a couple of different ones until I found one that reduced the bulb heat to a reasonable level). I rewired the interior light and it’s now connected to a decoder function output, so F0 activates the headlight while F1 activates the interior lighting. The result is a sweet-running unit with neat lighting effects. I still plan to experiment with the interior lighting in an effort to get a more even spread - currently considering glueing a strip of kitchen foil to the top of the light guide moulding to act as a reflector. Hope this is of use!