67 Parking brake light

[Durandal25]

So, the very last little issue I have with the MN Gold electrical is the parking brake light. I cannot seem to get voltage on it. Ground is good, and was trying to trace it back to the fuse block....but the wiring diagram calls for a blue wire but I cannot find a blue wire on the fuse block.
I'll add a few PICs

 

[Durandal25]

Here we go

 

[69L48Z27]

That light takes two possible grounds to work, one is the e-brake and the other is the distribution block. One or the other, or both. The diagram you have appears to be missing the distribution valve. Did you confirm that you do not have 12v+ with a test light or VOM?

I would also be using a wire chart from a factory manual. I’m not sure how accurate those aftermarket charts are.

Also, fun fact… that bulb is supposed to be a flasher bulb too.

 

[Nacho-RT74]

The blue wire is a constant 12 volts source straight from the RUN circuit coming out from ign switch somewher at a splice down the harness tape. Barelly on 72 this feed came out from fuse box due the increased devices to be feeded from this network, but untill 71 this source wasn't fused. At least for A and B bodies as far I know.

As mentioned, the black wire which is what turns on the light it with ground comes from dist brake block and emergency brake ( both linked ) so the light will turn on either when emergency brake is applied &/or a brake fluid pressure failure appears.

 

[Durandal25]

Here's the factory one, and it also has the wire listed to fuse block.....but as stated above, it must be a splice to the RUN circuit.

 

[Nacho-RT74]

I can't recall any pre 72 A or B body getting a fuse for the RUN circuit into the cab. This demands a fuse cavity divorced from any fuse box buss bar ( Batt or Acc ) and the only divorced fuse cavity on those is the cluster/dimmer light circuit as far I recall. Sure I can be wrong.

since 72 on E and B bodies, the two top fuses on both rows are divorced fuses from Acc and Batt bar busses, one for the cluster/dimmer circuit as earliers, then the RUN circuit but not for the ign system, just for the internal devices sharing this source like Brake cluster light, cluster itself ( on some models such as B bodies standard cluster ) and seatbelt warning system.

I think A bodies got that same mod for the extra fuse

 

[Durandal25]

Also too, the bulb in question is a 257 bulb, and they are kind of rare. I may have found a NAPPA option and I just scored a few from Jackson Lighting

https://www.jacksonelectricsupply.c...MI5N-t0_yH8QIVGAutBh3BqwCiEAQYAyABEgIIRvD_BwE

https://www.napaonline.com/en/p/LMP257N?impressionRank=29

https://www.bulbtown.com/57_Miniature_Bulb_Ba9S_Base_p/b57.htm

 

[Nacho-RT74]

my car uses a 57 bulb on there. Same socket thought. But diff could be the size of the glove, wattage and filament kind

https://www.bulbtown.com/57_Miniature_Bulb_Ba9S_Base_p/b57.htm

Editing:
yeap, pretty much the same bulb 57 vs 257. The filament shape is diff which would mean a diff light radiation and wattage is slighty diff too. Aprox same glove size. 57 is available almost everywhere.

So if you can't get locally a 257 bulb I'm sure you'll get 57 bulb anywhere. But if you are going to pay shipping, I guess will be better to get the right 257, just for correctness, since both will work

 

[Durandal25]

Adding it to the list sir

Ahhhh, got to love the resource gathering.

 

[Nacho-RT74]

I edited a bit my previous reply.

the differences mentioned uses to be associated to the shape of the housing where socket is inserted and lense distance, to assure a better light radiation and heat dispersion, but both will find its purpouse in there about get you the brake warning call.