'77 124 - dash lights go off on high beam

[Rupesy]

Whenever I turn on the high beams, the dash lights go out. They only stay on when the low beams are on. Also, is it normal for the dash lights to only go on when the headlights are on or are they supposed to come on with the clearance lights position? Right now the dash lights only come on when the headlight is on.

Any Idea where to start looking? I have all the circuit diagrams and have sorted out most of the PO mess.

[vandor]

They are supposed to come on even with the clearance (running) lights.
Most likely the PO did something. On the diagram find where it is powered from, and make sure it's still connected to the same circuit.
Alternatively, check that the gauges get a good ground signal. I just added an extra ground to the gauges, as the fuel/water/oil gauges all used to go up 10-20% with the lights on.

[Rupesy]

I guess I need to keep digging. When the key is out of the ignition, I can turn the clearance lights on (no dash lights). When I turn the headlights on, the headlights do not turn on and the clearance lights go out(and no dashlights).
Two more questions to help with troubleshooting:

Can the headlights go on with the key out of the ignition?

The wiring diagram seems to indicate that I should be able to flash the high beams with the ignition on and all the lights off. Should I be able to flash my high beams with all the lights off (to signal people to get out of the way LOL!)?

This will help me to narrow down where to start looking. I already found a wire with a replaced connector on the end going into the head light switch. Will have to see where that goes.

[Zulu]

From the factory, the light system worked as follows:

With the ignition OFF:

- The running (or clearance) lights will turn on, with the instrument lights.
- The headlights will not turn on, and the running lights and instrument lights will go out when the switch is toggled fully.
- Flipping the high-beam lever will do nothing.

With the ignition ON:

- The running lights will turn on, with the instrument lights.
- The headlights will turn on with the clearance lights and instrument lights.
- Flipping the high-beam lever will switch off your low-beams and switch on your high-beams.
- You can flash both the high- and low-beams by pulling toward yourself on the high-beam lever.

[Rupesy]

Thanks for the feedback. After looking over the diagrams again and doing some circuit testing, I have a sneaky suspicion that for some reason the PO must have jumpered the dash lights to the low beam circuit (a quick fix). This would explain why I only have dash lights when the low beam is on and they go off on high beam (based on the high/low bean switch diagram). I think I know what I need to look for and how to test my theory. Vacation all next week, so no need to finish it tonight!

[Rupesy]

Also, I did find that I can flash my high and low beam with the lights off. Didn't know you had to pull the lever towards you ...duhhh. Anyway, I can't flash them with the ignition off, but it seems as though the power to the light switch is off when the key is off so that makes sense. Getting closer.

[Zulu]

Also, I did find that I can flash my high and low beam with the lights off. Didn't know you had to pull the lever towards you ...duhhh. Anyway, I can't flash them with the ignition off, but it seems as though the power to the light switch is off when the key is off so that makes sense. Getting closer.

Oops, I was wrong about that: you can't flash them with the ignition off. My lights are wired differently than stock and come on with the ignition off (a hacky solution for my driver until I get the project driving).

[GeorgeT]

While you are sorting this out, you should install headlight relays - they will take a hugh load off the ignition switch, the column lever and the dash panel switch plus you will have brighter lights.

[Rupesy]

Well, I pulled down the fuse panel for a closer look and found a couple of wires out of place, however, the circuit diagram isn't very helpful when it comes to what is going into the fuse location. Anyway, the wire for the dashlights was hooked into the fuse for the headlights (fuse 6 yellow and black wire) which explains why they come on only when the headlights go on. One of the wires for the clearance lights was actually on a fuse that had no power coming in (fuse 8, yellow and red). The other wire for clearance lights was on the fuse (fuse 7, yellow and black) coming from the headlight clearance light position. So after switching them around I found a combo that worked, however, it is not according to the fuse diagram. I tried putting them in that configuration and then everything worked, but the headlights came on when the headlight switch was on clearance only. I took some pics to show what I found and what works.

Actual location of the wires when I pulled it down


Wires in position that works. It seems like I can use either the yellow/black wire for clearance or yellow/red, but I have to leave one off(put back over in fuse 8 spot).


Here is the wiring diagram with the changes. No wires on fuse 6, two wires on fuse 7, put one back on empty fuse 8:


Finally a picture of where I am at right now! Did solve quite a few issues today so it was a good day.



Thanks for the suggestion on the relays for the headlights. Any recommendation on what relay to use?

[GeorgeT]

There is a member of this forum or another one that sells a relay kit that's has a straight forward installation. Do a forum search for "headlight rely". Also search the Mirafiori forum.