electrical and ignition #6 fuse question

[Conway]

Car is a 75 12 fuse car. According to the sticker under the hood, this location has the flasher system, the radio, the horn, and the back up lights. Why would everything on the fuse be working except the flashers and back up lights?

[esty]

did you check for power at the flasher & back-ups...

[Conway]

Yes, I've checked the circuit with every electrical test I know to perform. Everything has power, everything has continuity.

[Simeon]

Have you checked the grounds in the circuits ?

It takes two to tango.

[Conway]

Yep, all grounds are clean and tight.

[Hans]

so, ignition on, car in reverse, you get 12V at the hot wire behind the bulb and no light?

[pklym]

Dead bulb. Or if the power isn't making it to the bulb, bad reverse switch or loose reverse switch (located on the tranny), and bad or loose hazard switch or flasher relay?

[Hans]

On an old car, you should use a voltage tester rather than test lamp to be sure a full 12V are coming thru

[Conway]

Turns out I do not have power at the back up light bulb or the flasher bulb.  Not sure why I said that in the earlier post.  Let me give a little background here.  I've been dealing with this issue for 2 years.  I did a 5 speed swap last year, I had these symptoms previous to the swap.  Sometimes everything will work as it should, and other times everything is dead.

 

The back up light switch is new (and the correct one) and the wires are clean and tight to the connection.  I replaced the turn signal switch with a new one from blunt.  The hazard switch is new and has the correct pin out for my car.  I have 2 stock and working flasher relays, and I also have the electronic relay that people have been using (the symptoms are the same regardless of what relay is in use).  I took the ignition switch out and cleaned it, no change.  All grounds for the circuit are spotless and tight.  All wires leading to fuse #6 are intact, spotless, and tight.  With the ignition on I have 11.8 V at the fuse.  I took out the rear bulb trays cleaned and sanded the bulb contacts.  bulbs are new and fit fairly tight in the sockets.

 

What's really got me confused is when I turn on the hazard lights, all signals flash like they are supposed to.  Where does the turn signal switch get it's power?  As I understand it, the TS switch completes the circuit when engaged, so does the power come from the ignition switch?

 

The only places this circuit comes together is the bulb trays and the fuse according to the wiring diagram.

[Hans]

For the reverse light, just to confirm: ignition on, car in reverse, are you getting 12V at the wire that attaches to the tray? If not, I'd test output from reverse sender. Keep working back until you find the missing link.

There is a current post for 75 wiring diagram - that should tell you where 4 way gets power.

Edited August 20, 2015 by Hans

[AustrianVespaGuy]

No worries Conway, I think I have this mostly figured out for you.

 

First thing is to understand that the hazard switch is SUPER weird, and does get power from two places: Fuse 2 (hot all the time) so that you can put the hazards on with the car off, and Fuse 6, which generally speaking powers the 'normal' operation of the turn signals.  So really the hazards working and turn signals are separate circuits, so don't let that confuse you, but it also confirms that there is NOT an issue with the bulbs/wiring at the back of the car; our problem is most certainly up front somewhere.

 

Now, both Fuses 5 AND 6 get powered by a solid purple wire coming from the ignition switch.  So if BOTH your wipers AND your reverse/signal lights don't work at the same time, then the problem lies along this solid purple wire (at the ignition switch, at the supply to the fuse box, or a break in the wire).

 

Next, check if the horn works, as it (along with the signals and reverse lights) is also supplied from the output from Fuse 6 (purple/white wires).  If the horn also doesn't work, then the problem is either A.) you have a shitty fuse/fuse connection, or B.) the purple/white wires are not properly plugged into the back of the fuse panel.  I think that one of these is the most likely cause.

 

If the horn DOES work but the other two still don't, then the last place the problem can be hiding is a break somewhere in the purple/white wires between the fuse box and the hazard and reverse light switches.

 

So in summary, test your wipers and horn, then based on that follow the above steps and you'll find the problem!

[Conway]

AVG, you were 100% right. Loose purple/white wire at the fuse box. I'm gonna go punch myself in the face.