Brake & Seat belt light................help (1 Viewer)

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So after owning my '78 FJ40 for one year, the idiot lights stopped working. Replaced both bulbs even though the originals looked good-still no dice. Got out the owners manual but could not figure out what fuse controlled these lights, and the fuses do look good. As far as I can tell all connections are good too. Anyone have any ideas???
 
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pngunme the drivers seat connection appears good. The brake masters are also full with no leaks......I believe the brake light issue is related to a switch on parking brake?????
 
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Those lights should have a constant 12v going to both when the ignition is on. Both the seat belt and the brake switches provide a ground to activate the lights. If neither works, I would suspect that you lost the 12v supply. It is a fused connection, so you might check your fuses for good connections.
 
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Could be the contacts on the light sockets - I would start with the light sockets and work my way back to the fuse box, to fuse #5. Check continuity and look for insulation nicks and/or burns, from arcing.

Note: I don't know that these are controlled by the heater fuse, but @spotcruiser and @bj40green know much more about this than I do.

Also, @DougAustinTx knows much more than me (who doesn't!) and he said, "Both the seat belt and the brake switches provide a ground to activate the lights." - where is the ground and does it need to be cleaned? Use dielectric grease on all cleaned connection points.

hth
 

bj40green

Tssss, tssss
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I'm on a little vacation this week and don't have access to my database with diagrams, so I can't be much of a help this week.
I'll follow this thread and check in after the weekend.
Hope you solve it sooner.

Hasta luego amigo's

Rudi
 
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Get a $5 multi-meter at Harbor Freight and see if you have 12v at the sockets with the ignition switch on. If not, your fuse holder could simply be corroded. My headlights kept going off on my '79. I traced it back to the fuse block where the fuse was good, but it was intermittent on making contact. Unhooked the battery to avoid shorts, then pulled each fuse out and ran a stainless steel rifle bore brush through each pair of fuse clips. (and No, I don't use a stainless bore brush on rifles..... but I had one just in case).:) Do that and at least you'll know that the fuses are making good contact and can troubleshoot elsewhere.
 
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You should pick up a Haynes manual for your vehicle at the very least. They have a good diagram for the 78 as well as the other later years to 82 if you get the right one. First version was just 76/76. Shortly after was 68-77. Then after 82 the 68-82 version came out. 78-82 items that were different were added to the back. The US 78 FJ40 wiring diagram is the first in the back section. The brake warning light should have power once the ignition switch is on. The seat belt warning light goes thru the seat belt warning relay first. When working this will only have power to the light for a few seconds and not at all if the driver's seat belt is latched when the ignition is turned on. If the Haynes manual is correct the wire from the fuse has one branch going to the gauges. main wire then has branch for the seat belt warning relay/light, next is the heater followed by reverse light switch/lights. Then ends with the brake warning light system. Have you checked if your heater and reverse lights to see if they work? Did both lights fail at the same time? Been many years since I worked on my 79seat belt warning light. I can't remember if it has a buzzer for the key in the ignition or seat belt warning or both. 78 diagram doesn't show a buzzer.:meh:
 
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Yes, both lights appear to have stopped working at the same time. My manual shows heater fuse/circuit controlling much more as well, will start checking all contacts.
Fuse1.JPG
 
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I don't believe mine has a buzzer, I do have the Haynes manual as well and a voltmeter somewhere......Thanks for pointing me in the right direction guys
 
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Couple of partial diagrams-one for 78, one for 77--ignore the circled part of the circuit on the 78. Seat belt stuff is toward the top-- Igniitor wiring-1978.jpg
Igniitor wiring-1978.jpg
77 fj40 starter wiring2.jpg
Igniitor wiring-1978.jpg
 

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