282 gantry crane

It sounds like a low-voltage situation that is occurring when the magnet and the motor are both drawing electricity.  Can you compare the voltage, specifically, at the magnet leads, both when operating the motor and when the motor is not activated?  ISTR that the leads to the magnet are somewhat flimsy, in order to be flexible. What gauge wires are you using to feed the controller? Can you raise the voltage either from the RW or provide more voltage from some other source, temporarily? Or temporarily install heavier gauge wires to the magnet?

This is really helpful, Arthur.  Thanks.  I'm using 18 AWG.  Would 14 or16 be preferable to feed the controller in regard to the somewhat flimsy magnet leads even though the accessory itself is rated up to 16V?

The power to the magnet goes through an insulated pin in the center of the rotational shaft.  There is a spring contact that sits on top of it to conduct the voltage to the magnet.  Check to see that that this connection is clean and there is tension on the spring.

I'm assuming that it's indeed a contact problem, as elucidated by the 282 service manual and by your reply, David, as well as this one on the Classic Toy Trains forum, which makes the identical point: "Lack of tension, and/or dirty contact surfaces, will cause intermittent contact when the crane is rotated, or when the winch is operated."  Before I start tweaking the two wire contacts at gear shaft and spring-loaded pin, one pertinent detail: the magnet does function when the first lever controller is down and the center lever is up, i.e., when the solenoid is activated, lowering the big hook.  It loses magnetism, however, when the first lever is shifted to the up position, i.e., when the hook is raised. Vibration in both directions, though.  In short, even though the magnet will work, the whole mechanism does not successfully pick up and then transport a magnetized load.

In another diiscussion on this topic from a few years ago which recommended rewiring the magnet and connecting it to a separate transformer (no can do, in my case), another member suggested, "Run the magnet very briefly in the opposite direction when stopped (up, if going down, down if going up) and you should hear the solenoid disengage.  Then you can lift/lower your load without the crane rotating."  I've tried that trick, but the problem persists. Any further speculations or advice before monkeying with the contacts?

I would try the easiest, first:  Clean the contacts, and increase the size of the power wires from the transformer to the controller.

Thanks, Arthur.  The feeders are 18AWG.  Would you suggest 16?  Also, I'm using the B-D posts (15v)  on my RW accessories transformer, but it's been suggested I increase voltage, too.  A-D would give me 19v--which might, however, overload this particular power source which runs other accessories.

It may well be something amiss in the controller.  The magnet loses power at the exact moment that the center (winch) lever is engaged upwards.  It will maintain magnetism if the crane is rotated right or left and even winched downwards.  But it loses contact when hoisting.