NO Brake Lights!

[fastboatman29212]

Sawyer's720 said his Brake Lights don't work but all the other stuff is working. So I assume the blinkers and marker lights and 4 ways and headlights all work properly.

I have an '86 720 but I use an '84 Service Manual for my info. Not much changed from 84 to early '86.

OK, Follow your brake pedal up under the dash. It will have a rod connected to it that goes through the firewall and goes to the brake master cylinder. You will also see a bracket. The brake switch is mounted on the bracket. When you press the brake pedal, the little button on the brake switch is released. The photo below shows the switch pretty clearly. This is the first time I have looked at mine since I got the truck and I see someone has wadded up a little duct tape as a small pad between the pedal bar and the switch button. My finger is pointing at the duct tape and that is where the button is located. Anyway, check to see if the button is stuck. If the button doesn't pop out when you press the brake pedal, then the brake lights won't come on. If the switch itself is bad, then the truck brake lights don't get the connection to turn on. It's literally an on/off switch. The Service Manual calls it a STOP LAMP SWITCH.



Autozone or other parts supplier may carry an aftermarket switch. I have not checked much for availability.

Of course, if you have a short somewhere in the wiring of the switch or other place in the circuit, that could be the problem too. So before you go and spend money on a new brake switch, check to see if it is really bad or not.

I hope that helps. Let me know.

[sawyer's720]

no the switch works. when i push in the brake in pops out. the fuses are good. and the bulbs are good so there must be a short somewhere right?

[fastboatman29212]

OK, the button might pop out, but that does not necessarily mean the switch is still good. Just like the light switch on your refrigerator door, it might move in and out, but the switch itself could still be bad and thus the light doesn't come on. Excuse my simplistic analogy.

I suggest that before you go to the trouble of removing the switch, trace the wiring from the switch and look for a break or short somewhere.

If you don't find any, try and see if the wires at the back of the switch will unplug, or whatever. If you get them off, then if you place a connecting wire between them, or touch them together, that should make the brake lights come on. It is a simple test that can (hopefully) be done before you remove the switch.

Let me know what you find.

[fastboatman29212]

Looks like eBay sells a replacement brake switch for the 720 in case you need one.

http://cgi.ebay.com/ebaymotors/Beck-Arn ... 35ac00fa66

[noface]

un plug the connector at the brake switch and use a jumper wire to short the harness connector pins together to simulate the opening and closing of the switch.

Or use a volt meter to check for voltage...

[sawyer's720]

the black connector piece has a tab on it, as does the clutch switch connector piece. but the only difference on mine at least, is that the brake connector piece tab sticks out/is broken and the clutches in not. could that have anything to do with it?

[fastboatman29212]

That's probably it then. Unplug the 2 Yellow wires (yellow with red stripe and another yellow with blue stripe) from the back of the brake switch and connect a jumper wire (green in photo) to the connectors. The brake lights should come on. If one of the metal tabs on the back of the brake switch is broken, then you will need to buy another brake switch.

[sawyer's720]

the wires don't pull out,not easily at least, should i keep pulling? i'm worried about breaking something.

[fastboatman29212]

I would undo the nut that is closest to the end with the button. Keep the other nut like it is. Slide the switch out of the bracket. Then see what happens if you just place a jumper wire across the two wires. That should bypass the switch and make the brake lights come on. You could also try a little WD40 on the connections to see if that helps loosen things up to get the clips off.

[sawyer's720]

my buddy and I took everything apart and we believe it is a trailer set up. the PO's set up trailer lights for the truck so when it was pulled behind an RV or what have you it could have working lights. this trailer light set up has no power so we are clipping and capping everything to see if it fixes the problem

[fastboatman29212]

So did the brake switch test OK?

[sawyer's720]

yeah the switch tested fine, and all the wires and fuses did as well.

[fastboatman29212]

Sounds like you've narrowed things down a bit. That's good. Maybe the brake lights were hard wired to the RV and all you need to do is re-establish the connection to the truck. Kinda hard to say without seeing it in person. Keep us informed.

[sawyer's720]

yea that's what we're thinking. we'll be fixing it soon, as for now we are helping my other friend perform an engine swap. after that's taken care of we should be fine.