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light switch problem

1K views 1 reply 2 participants last post by  J_C 
#1 ·
my 2010 Sport trac headlights will operate manually but at night when the light switch is in the auto position they will not turn on
 
#2 · (Edited)
I don't have a wiring diagram for your '10 but looking at an older generation diagram for the autolamp feature, you should check your owner's manual for the fuse diagram and look for one named something like autolamp or mirror sensor, etc It's most likely in the interior fuse box, not the one under the hood.

Next you could check to see if power is getting to the mirror assembly, and if when it should be turning the lights on, there is power going out from it to the headlight relay (relay coil pin). You can figure out which wire goes from the mirror to the relay by using a multimeter in continuity mode, or if none of the wires are continuous to either of the headlight relay coil pins (there are two of them) then it seems likely there is a break in the wire or bad connector along the way.

Of course the most likely suspect would be that you just have a bad switch. You could try spraying contact cleaner in, but in this case I don't know if it would do anything bad to the back coating of the mirror, ideally you would disassemble the mirror housing enough that contact cleaner only gets on the switch.

You might check at junkyards to see how much the mirror costs.

Another thought is I don't know if the ambient light sensor is in your mirror or mounted remotely. In some vehicles it's on the dash. If it is damaged, or the wire to it, you might just need that.
 
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