Need some help with wiring. Brake lights and turn signals arnt working. Headlights do work and when they are on the side lights come on as well as the brake lights. However they will not blink or light up anymore even though they are lit up.
Is this an issue with the combo switch or brake switch?
That's an odd one. Maybe a bad ground? Bad grounds tend to cause all sorts of weird problems.
Although your taillight description reminds me of a time when I installed an aftermarket stereo and tried to use the stock ground wire. It knocked out my taillights and dash lights. I replaced the blown fuses and moved the ground wire to the nearest shiny piece of metal and all was good.
Have you done any work on the car recently?
In reply to Hungary Bill:
Havent done much. Just cleanup really. PO had an aftermarket stereo by the look of the dash. May check the grounds tomorrow.
Are you sure the bulbs are good? Often tail lights and brake lights are either two different bulbs in the same light housing, or even two different fillaments in the same bulb.
I get that it is unlikely for both sides to have the same failure though.
Start with the easiest and go from there. Bulbs, fuses, grounds. What kind of car? An older one will have a painfully simple wiring diagram and you can probably trace it to the circuit that has both brake lights and turn signals to locate your problem.
For example, both the turn signal and the brake light probably use the same relay to light the brake lights...
Its a 1982 rx7. And didnt check to see if both filaments are good in the bulbs. Might be worth a shot.
One of the rx7 I wired from scratchhad ssome sort of computer/module that all the turn/brake lights ran through. Does yours?
In reply to Dusterbd13:
There is some kind of secondary ecu looking thing towards the back of the car. All the connections are good and none of the components look fried but I could be wrong.
Take some time looking through this:
Page 23 should be a good start. You can then start checking things that run on similar circuits to what is and isnt working to pinpoint the problem. Like, does the horn work? That looks like it shares a power feed with the brake lights. Also, do the headlight motors work? Looks like they share a fusable link with the turn signals, brake lights, and horn, but the headlight bulbs are on a separate circuit.
In reply to rcutclif:
Ive been using that diagram but I am admittedly quite lost when it comes to wiring. The headlights qork perfectly but the horn does not. When the horn is pressed a clicking noise comes from one of the relays under the dash. Is it possible that relay has gone bad?
Could be. Can you find the relay? If so the relay can be troubleshot easily enough with a multimeter:
remove the relay and look at the four prongs.
with the multimeter on the resistance (ohm) setting systematically probe the prongs until you get a resistance value between two of the prongs (there is often a diagram on the side, but it's only 4-prongs, so random searching isn't impossible). These two prongs make up your coil line.
make a set of jumpers to apply 12v to the coil line (the two prongs) you should here a click. Directly to the battery is an option for a 12v source. I've also used two 9v batteries in a pinch.
with your multimeter still set on the resistance (ohm) setting probe the remaining two prongs (this is the switch line). You should have continuity here while voltage is applied to the coil. You should have no continuity when voltage is removed. (continuity = a very low resistance value)
Good luck!
Never use an ohmmeter where there is a possibility of voltage in the line.
edited to specify "remove relay". So no possibility of voltage.
Gonna check it after lunch.
If you can hear the relay click I doubt it is your problem. Usually when you can hear it click when you press the switch that means it is good. Not always, but usually.
Looking at that page 23. Can you see how the line goes from the battery, through a couple fuseable links, then to the horn relay coil? curly-q looking thing. Then after that it goes to the horn switch? Basically a relay is an electrically activated switch. When you put current through the coil, the other circuit connects (and you can usually hear that happen - its a physical magnet pulling two contacts together). So therefore, I believe you have power getting to your horn relay, and probably going through, but either not getting to the horns themselves, or they might be broken.
Additionally, this is good news, because it means that if you are getting power to the 'top' of your horn relay, you should also be getting power to the 'top' of your brake light switch. (see how they share the same line in the wiring diagram?)
My next step would be to push the brake light switch (should be attached to the brake pedal somehow) in, and check if you are getting 12V at both pins (or, it might be easier to take the switch out, and then make sure that it has continuity when the switch is activated and it doesn't when it isn't). I would take the wiring diagram and follow that line all the way to the brake lights. When you get power (12V) on one side of a component but not the other, you have identified your component that is not working.
In reply to rcutclif:
Gonna check the switch when I get home from work. When I see the switch it has two sections. Both should be showing 12V correct?
I finally had time to look at the wiring diagram.
I'm going to say the horn relay should probably go into the "it can wait" bin. I don't think it has anything to do with the light problems. Instead I'm going to second everything Rcutclif said:
manually operate your brake light switch (at the pedal) and watch to see if the lights come on (did you say you already gave the bulbs a visual inspection?). We can safely say you have voltage at the switch, but we don't know if it's getting through when the switch is closed.
It should have 12v at both sides when you step on the brake pedal. Otherwise you should have 12v coming in, but not going out.
I have no idea what that "stop light checker" is that's called out in the diagram though...
Another way would be to jump straight to the end and get a volt meter and see if you have 12v at the light sockets (when the switch is activated). If it's there then you can make sure the bulbs are seated correctly and have good grounds. If it isn't there then like rcut said: "when you have 12v going in a component, and nothing coming out, you have your culprit"
The blinkers not working:
Do your hazards work? If they do then we've eliminated everything down to the "combination switch" (your blinker stalk switch). If they don't then we're probably looking at the CPU or that 10-amp fuse. (at least according to the diagram, but I don't see a flasher unit anywhere. Maybe it's controlled by the CPU?)
Good luck!
Hungary Bill wrote: I have no idea what that "stop light checker" is that's called out in the diagram though...
It's a box that lights an idiot light on the dash when a light blows. Common failure point on a lot of Japanese cars from that period.
Hazards do not work. Finally got voltage at the brake light switch. Car has to be in the on position for there to be voltage across both. Still not getting light however. But we took the combo switch off (was incredibly dirty and had several dead bugs between contacts) and Im hoping that once we get it back on everything will be fine.
Kenny_McCormic wrote:Hungary Bill wrote: I have no idea what that "stop light checker" is that's called out in the diagram though...It's a box that lights an idiot light on the dash when a light blows. Common failure point on a lot of Japanese cars from that period.
Awesome! So removing the connector from the stop light checker and jumping the green wire to the white wire (a paperclip might work) may omit that from the equation. If the brake lights work with the jumper in (and the brake pedal pressed) then the stop light checker is your culprit. If they don't then we move on down the line. It'd be a good idea to see if you have 12v @ the white wire on the stop light checker and good ground at the "b" wire (could be blue, could be black) first.
Hazards and blinkers:
Could be the 10-amp fuse, could be the control processing unit. I'm not entire sure about this but we could try removing the connector from the CPU and installing a jumper from the green-white wire on the plug to the green-black (could be green-blue) wire on the plug.
What has me questioning this idea is I don't see a "flasher" anywhere in the diagram. I'm assuming the CPU does the "flashing". If so then the lights would be on solid when the jumper was in place. Probably no big deal but I thought I'd tell ya. (jumper in, switch on. If the lights turn on then the CPU is the culprit. if not then look for that 10-amp fuse)
It'd also be a good idea to see if you have 12v at the green-white wire of the cpu (switch on) and a good ground at the blue (could be black) wire.
Fun times man, but it looks like you're making good progress.
^ the above is assuming, of course, that cleaning the bugs didn't fix it 
Also, please take proper precautions when installing and removing the jumper (De-energize the circuit, etc)
Cheers!
Update: Have power where there should be under the dash. Thinking the brake light switch is bad as the values were reading all over the place and never settled down. Going to pull one from the salvage yard tomorrow. Hoping that solves the problem. At the very least it will drop a variable from the equation.
Update: new combo switch in. Didnt change anything... Going to jump over the stop light checker tomorrow and then see if that does anything. Still have to see if the switch is good now that I cleaned it and test the sockets. How should I do that? Test the side or the contacts?
The brake switch? Probably the best way is to see if there is 12v at the stop light checker's white wire when the brake pedal is pressed. (disconnect plug and put the positive probe of the meter on the white wire and the negative on anything shiny and metal).
You could also check the switch by setting your meter to resistance and probing into the switch (disconnect plug, and go to the switch side of things). If resistance drops to near zero when the switch is pressed then it should be good.
I would probably trust the 12v method at the white wire a bit more. If you're still getting erroneous readings there then I would say to replace the switch.
Good luck!
This thread is fascinating, and a perfect example of why this place is great.
This IS Grassroots.
I'd put that lamp failure sensor box at high priority. They can cause all sorts of havoc, no harm in bypassing it entirely either.
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