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64 1/2 D Code Coupe,
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Discussion Starter #1
The brake lights stopped working on my 64 1/2 coupe. I disconnected the wires on the pressure switch under the hood and shorted them together (closed the circuit) and the brake lights came on just fine. So I thought it was the switch. I went and got a new switch, installed it, hooked it up, pressed the brake peddle....Nothing, No brake lights. I did upgrade from drums to front discs with an adjustable proportional valve. The stop light switch is connected to a port in the top of the valve. Before the upgrade the switch was in the single bowl master calendar, Now I have a dual bowl MC. The lights used to work after the drum to disc conversion. I switched to LED rear light panels a couple of summers ago. The brake lights worked great after installing the LED lights and they work great when I close the circuit as I mentioned above. It was in December 2019 that I noticed that they didn't work. Could it be the proportional valve? I'm assuming it's not the switch, old or new.

Thanks

Tom
 

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A photo of your "proportional" valve showing where the brake light switch is attached would be of great benefit.
 

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Check under the dash to see if there is a brake light switch that's actuated by your brake pedal. Usually, the switch on the proportioning valve is for a brake warning switch.
 

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Hmmm… Did they ever work with the switch on the proportioning valve?
 

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64 1/2 D Code Coupe,
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Discussion Starter #6
64 1/2s don't have and a stop light switch connected to the brake pedal. The pressure valve originally connected to the MC is what activated the brake lights.
 

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Discussion Starter #7 (Edited)
Hmmm… Did they ever work with the switch on the proportioning valve?
Yes it was working last summer. I noticed it wasn't working in December. I began to trouble shoot it and figured it must be something between the pedal and the proportional valve not activating the switch. I'm going to test the old switch and with an ohm meter and a little air pressure and see if that closes the switch.

Just tested the old switch, I put alligator clips on the connectors, connected the leads to my ohm meter and used a small screw driver to press the contact plate inside the switch. No resistance.
 

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I had never seen an aftermarket adjustable PV with an extra port for a switch so I didn't understand what you were doing. After searching for a SSBC PV I see that they did make such a thing. Apparently somthing inside the PV is blocking pressure or your switch is defective. I'd remove the switch and have a helper lightly step on the brake pedal and see if any brake fluiid comes out of the port.
 

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If it were me, I'd put an IVF "tee" into the rear circuit port on the M/C and put the switch there.
 

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^ Yeah. What the two posts above said.

Either you have a bad switch or something is going on in the PROPORTIONING valve.
(assuming the brakes are behaving exactly the way they did in December when the brake lights worked)
Outside of fooling around forever with it, you could "upgrade" with a brake pedal mounted switch....

And, you apparently have some leaks/weeps in your brake plumbing.

ex-Global West GM
1991-1995
 

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Discussion Starter #11
^ Yeah. What the two posts above said.

Either you have a bad switch or something is going on in the PROPORTIONING valve.
(assuming the brakes are behaving exactly the way they did in December when the brake lights worked)
Outside of fooling around forever with it, you could "upgrade" with a brake pedal mounted switch....

And, you apparently have some leaks/weeps in your brake plumbing.

ex-Global West GM
1991-1995
I spilled brake fluid filling the MC
 

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Discussion Starter #12
Update, I replaced the switch which and OEM switch and the same thing. No brake lights. I went and got the same switch that was in the SSBC cliip that awhtx posted. Brake lights work again.

I wonder what the difference between the Ford OEM switch and the switch that SSBC used. SSBC used a switch that was OEM to a 1968 Jeep CJ5 I found out. If this fails, I'm going to a pedal mounted switch.
 

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Anything can fail. There are a multitude of threads on the pedal-mounted switch. I've had an interesting time with a few myself. On the other hand, I do the maintenance on a 1942 truck with a pressure switch, which may be original. It works. As long as your system works, leave it alone. I'm guessing the failed switch is just that, a failed switch. The system of using a pressure switch is fine.
 

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I have no idea why Ford changed from the pressure switch to the brake pedal switch. Would you rather work on a switch that you merely lean over a fender to reach or one that you have to lay on your back under the dash to reach?
I have a '58 F600 with the pressure switch and it looks like a 62 year old original to me.
 

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No doubt it was cheaper.
My guess is that the Fed's had an issue with the potential of the brake lights failing to come on if there was hydraulic failure in the brake system. Also, with the advent of dual-circuit braking coming along (the manufacturers would have known this in advance) that having 2 separate circuits it would be necessary to have 2 separate switches thus becoming a cost and complexity factor.
 
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