Brake light fuse...?

Wiring, lights, heater controls, anything electrical..
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ischilf
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Brake light fuse...?

Post by ischilf »

Hello all. I am trying to figure out if I need a new brake light switch or if I am not getting power to the switch. I have ordered 2 switches just in case.

The pickup is a 1970 W200. I have poked the red wire coming out of the switch (to the best of my understanding that is the hot wire) with a test light and no light. I have also tried the white wire and no light. This tells me that I have no power to the switch. Searching the forum has other people mentioning that there is a fuse the brake light gets power from. I have checked all fuses and they appear to be good, with the exception of the horn fuse. The only lights I do not have working at the moment are my brake lights. I have all other lights working, running, turn signals, and headlights.

Does anyone have suggestions?

Thank you,

Ian

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Re: Brake light fuse...?

Post by Johninky »

Check for power at that switch above the brake pedal.

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Hobcobble
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Re: Brake light fuse...?

Post by Hobcobble »

ischilf wrote:Hello all. I am trying to figure out if I need a new brake light switch or if I am not getting power to the switch. I have ordered 2 switches just in case.

The pickup is a 1970 W200. I have poked the red wire coming out of the switch (to the best of my understanding that is the hot wire) with a test light and no light. I have also tried the white wire and no light. This tells me that I have no power to the switch. Searching the forum has other people mentioning that there is a fuse the brake light gets power from. I have checked all fuses and they appear to be good, with the exception of the horn fuse. The only lights I do not have working at the moment are my brake lights. I have all other lights working, running, turn signals, and headlights.

Does anyone have suggestions?

Thank you,

Ian
I had a similar problem. Mine turned out to be one of the fuse end
clips in the fuse box. It was broken but I couldn't tell. It was when
I removed the fuse that half of the clip fell out. :pale I installed
a new clip and was back in action. :Thumbsup
John

ischilf
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Re: Brake light fuse...?

Post by ischilf »

Johninky wrote:Check for power at that switch above the brake pedal.
Physically above the switch or above in power flow? I have tried tracing the wire but it jumps right into my harness. I would personally prefer not to have to cut open the harness if at all possible.

ischilf
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Re: Brake light fuse...?

Post by ischilf »

Hobcobble wrote:
ischilf wrote:Hello all. I am trying to figure out if I need a new brake light switch or if I am not getting power to the switch. I have ordered 2 switches just in case.

The pickup is a 1970 W200. I have poked the red wire coming out of the switch (to the best of my understanding that is the hot wire) with a test light and no light. I have also tried the white wire and no light. This tells me that I have no power to the switch. Searching the forum has other people mentioning that there is a fuse the brake light gets power from. I have checked all fuses and they appear to be good, with the exception of the horn fuse. The only lights I do not have working at the moment are my brake lights. I have all other lights working, running, turn signals, and headlights.

Does anyone have suggestions?

Thank you,

Ian
I had a similar problem. Mine turned out to be one of the fuse end
clips in the fuse box. It was broken but I couldn't tell. It was when
I removed the fuse that half of the clip fell out. :pale I installed
a new clip and was back in action. :Thumbsup
John

What fuse is that you checked? I can not identify a brake fuse

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pwadventurer
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Re: Brake light fuse...?

Post by pwadventurer »

The brake lights are on with the dome light and the low brake warning lamp. It is the 4th fuse from the hazard flasher. Sits between the instrument lights fuse and the tail park lights fuse. After the fuse (red wire), there is a splice the splits to the dome light (yellow) wire and to the low brake warning lamp ( blue wire). The red wire continues to the bake pedal switch.

ischilf
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Re: Brake light fuse...?

Post by ischilf »

I checked the fuse and it's good. I have power on both ends of it. I'm not sure where the wire leaves the fuse block and ties back into the wire harness. Anyone know the physical location of where that red wire comes into the harness? I do not have power at the red wire going to the brake light switch.
I'm really confused by this.

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Re: Brake light fuse...?

Post by Hobcobble »

http://www.sweptline.com/tech/70wire.jpg
Try looking at this diagram. :study :Thumbsup
Another one of my Sweptlines had the left brake
lamp go out and it turned out to be a bad turn signal
switch [steering column].
John

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Re: Brake light fuse...?

Post by pwadventurer »

Having power on both sides of fuse does not eliminate broken fuse holder. It just says fuse is good and power on line side of fuse is good. Check back side of fuse block on red wire and see if 12 volts is there. It might come and go from twisting fuse block upside down.

You should buy or borrow a "volt/ohm" meter and check for continuity on all the wires involved. You should have continuity between red brake pedal switch wire to back side of fuse block, and to the blue wire for the low brake fluid lamp, and to the yellow wire for the dome light. All three wires are connected together. If you have continuity between all three, then splice is good and most likely like John said, you have a broken fuse holder, even though fuse is good.

Having a volt ohm meter with beeper on it make trouble shooting easier.


Also note that the red wire should be a direct wire to the brake pedal switch and the yellow blue wires should be tapped from the red wire.

ischilf
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Re: Brake light fuse...?

Post by ischilf »

This problem is confusing to me. When I put my test light to the fuse it lights up. When I pull the fuse panel off the firewall and test the wire going to the appropriate fuse I have no light. How come I have power at the fuse but not at the wire supplying power to it?
I have traced the wire to the engine side of the firewall and still no power to it. Does anyone know where the wire gets it power? I'll try it from the head waters and see how long until I'm powerless.
Thank you. Ian.
P.S. I did order a me brake light switch but that has made no difference.

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Re: Brake light fuse...?

Post by pwadventurer »

ischilf wrote:This problem is confusing to me. When I put my test light to the fuse it lights up. When I pull the fuse panel off the firewall and test the wire going to the appropriate fuse I have no light. How come I have power at the fuse but not at the wire supplying power to it?


maybe that's where the problem is , the connector or fuse holder is broke.
"ischilf" wrote: I have traced the wire to the engine side of the firewall and still no power to it. Does anyone know where the wire gets it power?
power comes from alternator, through firewall connector, then to fuse block via a splice.it also has the power coming from battery, through firewall connector, then through amp meter then to fuse block via same splice.
70 dodge brake wiring.png

ischilf
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Re: Brake light fuse...?

Post by ischilf »

In the picture you posted, are the colors correct representations of the wires on the pickup? It appears to me that the ones I've seen are. If that's the case this might make it a lot easier haha.

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Re: Brake light fuse...?

Post by pwadventurer »

Yes

ischilf
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Re: Brake light fuse...?

Post by ischilf »

So after replacing the light switch and looking at all sorts of writing diagrams I figured out the problem.
The fuse wasn't making good connection on the output side.

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Re: Brake light fuse...?

Post by PwrWgnDrvr »

That's a common problem due to rusting of the tangs that hold the fuse in the block. It can even be a bad connection between the tang and the rivet that holds the tang to the block, also due to rust.

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