3rd Brake Light/Back up Light dont work

Miller220 · Nov 13, 2009

Hey! Ok, so my car hasnt had any backup lights since I got it last august or so...which I figure is no problem, I'll just replace them later. So while I was doing my brakes..I found a random set of new brake lights in with my spair tire, which again wasnt a Problem. NOW, when I pulled out the assembly and the back up light(the lil white one since I think I made up the term) Was ALSO new...but it also didnt light up.

Long story short, I swapped the bulbs, brought out my brother and he said that it didnt work, along with the light above it(it being the lil white thing, along with the brake light above it). I plugged in the other light, and there was the same problem. Am I to assume that I blew a fuse? If I did(which I'm assuming that the car came with a blown fuse) any idea WHICH fuse and where to find it? Any help would be appreciated, seeing as I wouldnt mind seeing behind me while I back up at night.

Thanks!

wmburns · Nov 13, 2009

The back up light is on fuse F2.11(15a).

The 3rd brake light is on fuse F2.33(15a) F2.41(15a).

Is the "little white thing" the license plate light?

Sooooo. No fuse in common. However, it is not a bad idea to check all of the fuses.

Recommend start out by checking grounds. Measure the ohm between the empty light socket and a known good ground. Optionally, test for 12 volts from the other side and a known good ground. Post the results.

Has there been any audio work or body work done?

Has this been posted before?

Miller220 · Nov 13, 2009

Now that I think about it...the left light over my plate is also out...along with 3rd Brake lights, and back up lights are also out. If there isnt any fuse in common...and I DID switch out one of the back up light with a new light that was right out of the packaging...and It was the right bulb(Something that ended with L's. I dont remember it all..but was the same light that I pulled out). The bulb that was inside was new....so I dont know what it is...Any ideas at all? I will check the fuses though, just for good measure.

wmburns · Nov 13, 2009

Sorry. Already gave you my best ideas. Need to know the results of the test before going in a new direction.

Sappy saying for the day: "there is no elevator to success, you have to take the steps".

wmburns · Nov 18, 2009

G400 ground left side trunk

How are the tests going? Note, several components mentioned have ground G400 in common. However, if the full ground was bad, much more would be affected.

Please review the attached diagram.

IMO, it is more lilkely that some wiring/connector in the turnk has been damaged. You may have to remove the trunk liner in order to inspect. Follow the wire down from the 3rd brake light. Look for any signs of damage (esp water). If found, it will need to be repaired.

Do the same for the back up lights.

It would still help if we knew for certain that there is 12 volts in the socket (or not).

wmburns · Jan 15, 2010

2 rear brake lights bulbs on each side (by design)

OK. After a series of PM's back and forth, I think I have a better understanding of the problem. The OP has noticed that on each rear side brake light cluster there are 3 bulbs. When the brakes are applied, only 2 light up. However, when the parking lights are on, all 3 light up.

Rest assured that every late model Mustang does this. Two of the bulbs are dual filament (high/low) bulbs and the inside bulb is a single filament (low). The parking light use the low and the brakes use high.

Please review the wiring diagrams. Note on diagram 90-4 that there are 2 brake bulbs per side. On diagram 92-2, there are 3 rear parking bulbs.

Also, if the rear stop light assembly is removed, it can be seen that 2 sockets have 3 wires and one socket has only 2 wires. So it came from the factory that way.

If there is a problem when any other lights not working, please repost exactly which are not working and the results of the ground tests.

3rd Brake Light/Back up Light dont work

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