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Brake Lights Not Illuminating


Guy Cocquyt
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I have a 1970 '02 automatic.  I have no brake lights, they were working until quite recently and I haven't done anything to the wiring recently.  According to the wiring diagram in Haynes diagram (very difficult to follow due to print size and quality), the brake lights are connected to  the  #4 fuse (6 fuse panel) which also fuses signal lights and reversing lights. I checked bulbs, connections and fuse, all working OK.  Pulled the brake switch and tested it as working however the power wire to the switch is not registering any current with or without the ignition switch on.  I ran a wire from the battery to the switch and the brake lights came on.  I am trying to sort out the power wire.  It disappears into a wire bundle below the fuse box and looks like it is heading through the firewall.  Before I get under the dashboard I need some help with the following questions.

 

Should the brake lights be getting power through the ignition switch like the signal lights and backup lights?  I thought brake lights were always powered regardless of the ignition switch being on or off.  Can anyone shed light (pardon the pun) on this question?  Thanks, Guy,  Cochrane, Alberta

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Hi,

 

I am looking at a wiring diagram for a '75 so I don't know if things are exactly the same for your car.

 

What I see is that the ignition switch sends power to a violet wire (#87) in the Run position.  This wire goes to fuses 5 and 6, #5 feeds the brake switch.  Therefore, the brake switch does not appear to be hot at all times, just in the Run position.  I would start by checking if fuse #5 is patent.  Sometimes, these fuses look okay but don't make good contact in their holders.

 

Follow the wires to the brake switch and I think you'll find the culprit.

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Hi,
 
I am looking at a wiring diagram for a '75 so I don't know if things are exactly the same for your car.
 
What I see is that the ignition switch sends power to a violet wire (#87) in the Run position.  This wire goes to fuses 5 and 6, #5 feeds the brake switch.  Therefore, the brake switch does not appear to be hot at all times, just in the Run position.  I would start by checking if fuse #5 is patent.  Sometimes, these fuses look okay but don't make good contact in their holders.
 
Follow the wires to the brake switch and I think you'll find the culprit.
Thanks, that answered my question. The fuse is OK, so I need to trace the wire from the switch to the fuse.

As I ran a hot wire from the battery to the brake switch and got brake lights, I believe the grounds are good.

My money is now on a bad connection for the power wire to the switch.

Thanks guys.

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I'd first check the switch, since you've already located and checked the fuse.  The switch is located aft of the power brake booster--it's a small pushbutton affair with two lead wires.  

 

You can isolate the problem to the switch (not an uncommon cause of no brake lights) by jumping the two wires that are plugged into the switch (with the ignition on)  and see if your brake lights come on.  If they do, the switch is the problem.  You may be able to get it working again by using a screwdriver to press the pushbutton in, then let it snap out several times.  That may loosen any corrosion on the two contacts and make it work again.  If that doesn't help, new switches are inexpensive and easy to swap out.

 

mike

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I'd first check the switch, since you've already located and checked the fuse.  The switch is located aft of the power brake booster--it's a small pushbutton affair with two lead wires.  
 
You can isolate the problem to the switch (not an uncommon cause of no brake lights) by jumping the two wires that are plugged into the switch (with the ignition on)  and see if your brake lights come on.  If they do, the switch is the problem.  You may be able to get it working again by using a screwdriver to press the pushbutton in, then let it snap out several times.  That may loosen any corrosion on the two contacts and make it work again.  If that doesn't help, new switches are inexpensive and easy to swap out.
 
mike
Thanks Mike, I tried jumping the two leads while the ignition was on and no light's. I ran a hot wire from the battery to the switch and got power, so the switch is good and the ground is good. The fuse is good as I have power to the signal lights so it looks like power to the switch is has lost continuity. Will try to trace the power wire back to the #5 fuse and see if there is a break somewhere. God I love this stuff!

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Hi,

 

By signal lights, do you mean turn indicators?  Those don't connect to fuse #5.

 

From what I can tell, Fuse #5 directly feeds the wiper motor and washer pump.  The wire to the brake switch goes on to the wish-wasch interval relay.  Do your wipers work?

 

It sounds to me that fuse #5 is your problem.  As I mentioned, the fuse itself may be fine but the conical nose often wears out, resulting in loss of contact.  Swap it for another and see if the brake lights work.  It's very unlikely that you have a broken wire as these don't get flexed much.  Could be a bad spade but my money's on the fuse.

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Hi,
 
By signal lights, do you mean turn indicators?  Those don't connect to fuse #5.
 
From what I can tell, Fuse #5 directly feeds the wiper motor and washer pump.  The wire to the brake switch goes on to the wish-wasch interval relay.  Do your wipers work?
 
It sounds to me that fuse #5 is your problem.  As I mentioned, the fuse itself may be fine but the conical nose often wears out, resulting in loss of contact.  Swap it for another and see if the brake lights work.  It's very unlikely that you have a broken wire as these don't get flexed much.  Could be a bad spade but my money's on the fuse.
Healey 3000, you are the man! Replaced the fuse and the brake lights work. See attached photo, the sticker though hard to read has turn signal lights, back up lights and brake lights on #5 fuse. Because the turn signals were working I assumed the fuse was good. Now that I think about it, I had to find power for my turn blinker from another source. Thanks for your expertise.

fb56bc3fd1abdeed5f3c6d6305794021.jpg

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2 hours ago, Healey3000 said:

I'm curious now about the fuse distribution - perhaps the older cars are a bit different.

Pre modell 71 cars have only six fuses, and the circuit distribution is entirely different from 12 fuse roundies, which in turn are different from squarelights.

 

And to make matters worse, I've discovered there are some circuits on later cars that aren't noted even in the shop manual (seat belt warning light system, for example)--that causes all sorts of "fun" when you get a short in the un-documented wiring!

 

mike

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23 minutes ago, mike said:

Pre modell 71 cars have only six fuses

 

In order to confuse up any clearing, here is the parts manual's version of history.  Our 1600 was one of the last 500 imported into the US in March of 1971.  The VIN lookup notes that it is a pre-71 generation but that it is a 1971 car.  It has a six fuse box.  So, no more questions, right?

 

Moral of the story:  listen to the parts manual and Mike.

Fuse Box Parts Numbers.png

Fuse Box Parts Numbers2.png

VIN Decoder.png

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