Left turn signal inop when headlights on?

[duckkarl]

So my parents have a 2000 Mountaineer that has developed a turn signal issue. All signals work properly when the head lights are off. Once you turn the head lights on, the left signal will not illuminate. The local parts guy told them that they need a new flasher unit. Does not sound right to me seeing as the signals work with head lights off. I am thinking that the problem is more likely to be the MFS. I should also state that it has tilt steering. Does this sound correct to anyone? Has anyone seen this issue before? Thanks in advance for any advice you can provide.

 

[Runnin'OnEmpty]

My guess is that it's indeed the MFS giving the trouble.

My 2000 turn signals were coming on by themselves
because of a faulty MF switch. They have a history of
frequent failures, but they're very easy to replace and
not expensive.

 

[duckkarl]

My guess is that it's indeed the MFS giving the trouble.

My 2000 turn signals were coming on by themselves
because of a faulty MF switch. They have a history of
frequent failures, but they're very easy to replace and
not expensive.

Thanks for the info. That is what I was thinking too. Come to find out, the flasher didn't fix it for them. I am almost positive that the MFS will.

 

[bigcrunch]

check the ground on the turn signal socket.

 

[briwayjones]

Yup, sounds like the multi-function switch.