brake light troubles (again)

[Nicholas D]

Hello everyone, having an issue with my son's '89 Ranger that I'm hoping I can get some advice on. Basically, all the lights function except the brake lights. The hazards work as well, as I know these two systems share a fuse. A couple of weeks ago they quit working and it turned out to be the brake light switch under the pedal. I bypassed the switch and they worked, so it got replaced with a new one and it worked as it should for a few weeks. They quit working again but this time when I bypass the switch they still don't work. I guess the next step will be to check the wiring going into the brake light switch with a multimeter to make sure there is power at least this far. It's a real head scratcher and just curious if anyone else has experience with this. We had to replace the multifunction switch a year ago for another issue, and I don't think this switch would cause the brake light issue, but I am not sure. Any insight would be greatly appreciated! Gotta get this beauty back on the road!

 

[Li'l Work Truck]

Nice truck! Is there a brake light fuse?

 

[Nicholas D]

There is and it is shared with the hazards, which work. We checked the fuse already and it's good.

 

[RobbieD]

With a meter, check that power is going into the brake light switch, and then coming out when the pedal is pressed.

If that's good, the next thing is to check for is brake light light on power going into, and out of the multifunction switch (aka "turn signals") on the steering column. The brake light circuit passes through the multifunction switch, and they can get "finicky" with age. Check the terminals in the connectors there, too.

 

[Nicholas D]

Okay, thank you. Last time when I used a jumper wire to bypass the brake light switch I got brake lights back, so I knew the switch was bad. This time when I jump it I still don't get brake lights so I believe the switch is good. Sounds like I need to check for power at the switch plug and then go from there. Like I said, we replaced the multifunction switch a year ago but that really means nothing. Seems new parts are just a roll of the dice. We'll check this evening and see where we're at. Thanks again!

 

[Nicholas D]

Update, I've got power to the brake switch plug, but still no brake lights when I jumper past the switch. So now the plan is to check the brake light wire at the plug for the multifuntion switch. Not to get too far ahead of myself, but assuming I still have power at that plug, I'm not too sure how to check the multifunction switch itself. I really need to get a manual for this truck.... any input always appreciated! I see that it's the "511" tine on the plug, but still not sure how to check that.

 

[RobbieD]

I'm not too sure how to check the multifunction switch itself. I really need to get a manual for this truck.... any input always appreciated!

You can do a continuity check across the switch itself with a VOM meter; replacement parts are real crap these days. You also can supply +12 to the switch input terminal and meter the output terminal.


Two Phillips screws from below will let you loosen and then remove the column shroud. That exposes the multifunction switch.

Here are are the wiring schematic and troubleshooting pages from the factory manual:

In the schematic you can see how the stop lamp circuit routes through the multifunction, because the turn signal and hazard functions shares the same output circuits to the lamps. If only the stop lamp function is not working, I'd be looking real close at the input terminal from the brake pedal switch, the splice S218 and the plug at the brake switch.

The wiring manual is called an EVTM, and can be bought off eBay, cheaply if you're lucky or patient.

 

[Nicholas D]

Thank you very much for this, it is really helpful! Of course this happens when my work schedule is crazy busy so I'm not able to dedicate much time at once right now. Hopefully tomorrow I'll be able to dig into the multifunction switch a little.

By "input terminal from the brake pedal switch" you mean the plug from the brake pedal switch that goes into the multifunction switch? Sorry, I'm a simpleton, this is definitely not my strong suit. I feel pretty confident that the plug at the brake pedal switch is working because I got voltage when I checked it with the meter. Not sure what the S218 splice is either, but I'll do since investigating while at work tomorrow.

Thanks again, much appreciated!

 

[Nicholas D]

Just bought a copy of the Electrical and Vacuum Troubleshooting manual for $16 off ebay. Gotta love the good ol internet!

 

[RobbieD]

By "input terminal from the brake pedal switch" you mean the plug from the brake pedal switch that goes into the multifunction switch?

Yes. The wire from the brake lamp switch will be in the connector, or plug, at the multifunction switch. The wires are crimped into terminals, which lock into the connectors.

Look carefully at wires and terminals; they do, over time, back out of the connector body; get corroded, or loose metal tension and no longer tightly grip the mating terminal enough to make a good electrical contact. Heat from the resistance caused by poor connections builds up with use, and makes the problem even worse, until the circuit fails completely (becomes "open").

Excellent move on nabbing a manual. You'll be telling yourself time and time again, what a good investment it was.