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No Brake lights


finkiedog
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All of a sudden I have no brake lights and they did work before....where are the fuses that I should check? which ones? is there a relay in the front bonnet on passenger side wall that is part of the brake light? any thoughts??? This is a 1986 Jalpa

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Start with the basics:

 

- Check the fuse box. Passenger side under the front bonnet, big black box, has a thumb screw to take the cover off. I'm not near a wiring diagram so I do not remember which fuse it is. They are bullet style fuses, so bullet fuses have a tendency to sometimes fail in a manner that isn't always obvious. I'll take a look later tonight when I can access a wiring diagram.

- With the earlier Jalpa, it's likely that the tail light grounding is daisy chained. It was on the earlier harness I worked on that I'm using for my restoration. There is a piece of carpet in the back underneath the trunk latch that can come out. Once that is pulled, you should be able to see the black ground wire(s) on the tail lights. On the later car like mine, each tail light had one. On the earlier harness, they were daisy chained to one ground, which if it were to get loose would result in no lights.

- It's unlikely but be sure to check both bulbs if the tail lights aren't working.

- If the fuses check out and the grounds look good, the next thing to check is the brake light switch. You'll need a multimeter to do that, and then turn it on resistance mode. At the bottom of the master cylinder there are little switches with 2 prongs. Have someone touch both tester nodes to them, and then step on the brake. If it goes from open to closed, the switch is working fine. This means it's somewhere else in the circuit.

 

Try these first and let me know what you find. One thing at a time, always start with the basics.

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will start with that when I get home....thanks for the information. Did a run through the fuses...changed the Blue , White , and Red.....no brakes........opened rear bonnet.......removed carpet , found the ground, was slightly loose, removed screw buffet up metal and the 2 leads, reconnected tight....no brakes. Pulled the bulb, tested, both high and low working. cleaned up both connections at the master brake reservoir....re connected....no brakes. Will have to wait for 2nd person to test the switch

 

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Apologies, I gave you incorrect info on the actual switches. I'm finally home looking at it and I was thinking Porsche. They use check switches on the bottom of their masters. On the Jalpa there is a junction on the brake lines with a check switch that closes circuit when the brakes are pressed. I can't get a good picture of mine because there is a huge aftermarket alarm in the way. But if you follow the frame wall DIRECTLY down from the brake booster (basically follow the brake lines out of the master cylinder) you'll see a union joint where the brakes connect. Coming out of the top of that is 2 wires, this is your check switch.

 

It's part #27 on the front brakes diagram for the jalpa from Lamborghini.

 

I'll try and remove the huge alarm tomorrow and get a picture, but once the spare tire is removed, you should be able to pretty clearly see it below the brake booster. It'll be the only 2 wires coming out of a union with brake lines attached to it under the master cyl. All it literally does is complete the connection between the two wires.

 

The test will be the same, remove wires, put multimeter on check switch spade ends (one on each), hit brakes, if the circuit closes and resistance goes to open circuit then it's something else. If it doesn't, it's your check switch.

 

On the diagram it shows it facing down but in my jalpa it is actually facing up with a green stripe wire and a red wire.

 

You could also attempt to emulate the brake lights by using a test wire and jumpering the 2 female connectors that go to the check switch. However, in the diagram that I'm seeing, this is a 12v switched circuit, meaning it's hot, so be very careful if you do this as you don't want to short anything out (don't touch the frame or anything it could ground on). In jumpering it you'd be emulating what the switch would do. If brake lights come on, it's the switch, if not, it's likely something else in the circuit.

 

If you look at a wiring diagram for the Jalpa it's #18, the Hydrostop switch.

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Found the check switch...it is down there hard to get at ....I got the 2 wires off and have my battery cut off on so there is no power. when I check for power on the red wire it is hot 11.8 V.....and I check the yellow green and it is also hot 11.8V...? I s that the way it is to be? Not sure if I should jump them together?

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Took a chance and jumped the wires and the brake lights came on.......got the multimeter clipped on to the check switch and hit the pedal and the circuit closed ......hooked wires back up and Abracadabra!!!! brake lights!!!! Must have been a bad connection. Thank you for your guidance...GREATLY APPRECIATED!!!!! Now I can go for cars and coffee with that car.....I took my Urraco last time and the boys love seeing that one out as well.

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Took a chance and jumped the wires and the brake lights came on.......got the multimeter clipped on to the check switch and hit the pedal and the circuit closed ......hooked wires back up and Abracadabra!!!! brake lights!!!! Must have been a bad connection. Thank you for your guidance...GREATLY APPRECIATED!!!!! Now I can go for cars and coffee with that car.....I took my Urraco last time and the boys love seeing that one out as well.

 

Sounds like a dirty connector. If you want to make sure they don't give you further trouble, disconnect the battery and then spray some electrical contact cleaner on the spade ends for the switch and the wires and that'll help.

 

Last thing Mr. Kerplop.........if you could tell me which of the fuses was the brake fuse would be great.....Blue, White, or Red???

 

I'll take a look when I get home but I'm fairly certain it's fuse #13, should be an 8 amp fuse (white).

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