lights flicker when putting out slides

mholman wrote:
I have recently replaced all the 12 volt light bulbs with LEDs.
(cheap china)
I have noticed that with the lights off that when i first push the switch to put the slides out the lights flicker once.
any ideas?

your info on the LED's is the first clue. More than likely they do NOT have any voltage regulation, just a dropping resistor to sort of set the current to the LED's. So when you hit the slide switch, several things happen. First, the motor inrush current is very large, this drops the battery voltage. the LED's are extremely senstive to voltage across the LED a slight drop in voltage results in a big drop in light output. that drop may only last a fraction of a second, but the LED responds immediately. then as the voltage comes back up, they brighten up.

Next, as Mex mentions, inductive loads result in voltage and current spikes that can cause additional havock with this type of LED drive circuits. Try Mex's trick to see if it fixes it.

BTW I have LED's with real current regulation and filtering for spikes on the panel, they are basically imune to such issues, and are much brighter and will easily tolerate voltage spikes and voltage range from below 10V to above 18V with the same constant light output. But the cost is more than the non regulated ones.