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Not Enough Voltage to Brake Lights

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    Posted: 11-February-2024 at 5:21AM
1973 wagon. I had my power brake booster refurbished a while ago. The brake lights worked before I had the booster refurbished, but I put my brake light switch back in and don't have brake lights (I do have tail lights. The rear turn signals have always worked, the hazards worked before but not anymore, and I have a grounding issue with my front turn signals that I haven't sorted yet (I just have the three wires on both taped off with no connector or bulb right now). The brake lights work when using a power probe. 

I already had the instrument cluster out because I just cleaned out my fuel tank and had to do some soldering to make the fuel gauge work again. I unplugged this wire from behind the instrument cluster, which goes to the brake light switch:


I only have 9.5 volts at this connector where that other wire I unplugged goes:


I've been pouring over the service manual, wiring diagram, and previous posts here...and from what I've found, the green and pink wire goes to the turn signal switch, which should be this connector here, I think?


I'm also unsure of exactly what this connector is for, by the brake light switch:


After that point, I'm lost. Could it be a problem with the wiring in the turn signal switch connector? Do I just need a new turn signal switch and/or flashers? I just know I have to have brake lights if I'm gonna drive on the road...
Griffin
1973 Gran Torino station wagon
1972 Gran Torino 4 Door
1971 Maverick 2 Door
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 11-February-2024 at 6:18AM
it's been eons since i've been there myself with an operational fuse box but is there a brake light fuse? i'd be checking the entire fuse block for signs of corrosion / oxidization that could be inhibiting the Angry Pixies from doing their free electron dance. it might not even look like there's anything going on but just a little patina can do it, ever hear of DeoxIT ?

https://caig.com/deoxit-d-series/ pick your product and search for best price. i'd be doing every connection you can access! also don't overlook the fuses themselves, they can actually corrode internally, just because you don't see it totally blown doesn't mean it's Good
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GTW Quote  Post ReplyReply Direct Link To This Post Posted: 13-February-2024 at 1:10PM
There is a stop light & hazard fuse according to the shop manual. I’d be very relieved if the problem were just that fuse. I’ll try replacing it. I should’ve included a picture of the fuse box, but I’ve never heard of that Deoxit stuff before! With my wagon having been off the road for 45 years this month actually, it probably could use some. 

I’m still wondering if I actually reached the turn signal switch though…and about what to do if the fuse/fusebox isn’t the problem.
Griffin
1973 Gran Torino station wagon
1972 Gran Torino 4 Door
1971 Maverick 2 Door
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72FordGTS Quote  Post ReplyReply Direct Link To This Post Posted: 13-February-2024 at 1:42PM
While you are at the fuse box, have you measured the voltage from the fuse box?  I would do that and then follow the circuit and check the voltage at various points to see where the voltage is being lost.  I would also double check all your grounds in the circuit, remove them and clean.  It might be worthwhile to look at the brake light switch itself.  I have a had a few go bad over the years, but usually you just get no brake lights when it fails. 
Vince

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