brake lights out when lights are on, but work fine when lights are off?

[RodeoLS2000]

Hi everyone!

someone told me that both my back brake lights were out on my 2000 Rodeo LS, except for the window brake light...that works ... but they are only out when the headlights/parking lights are on ... when I do not have any lights turned on the brake lights work fine... anyone having this problem?
... just wondering if it is the bulbs or fuses... before I go into replacing everything.. thanks for any help or advice.. appreciate it!

[amigo-2k]

if you have a trailer harness plugged in try unplugging it and see what happens.

This is the number one cause.

[dropsnout]

the bulbs are shorted internally replace the bulbs and everything should be good

[Ezlivin]

I had the same problem,lights off and the radio lights would come on, with the lights on the cruse control would go off . I took the trailer light harness out and everything works