412 wagon headlights not working

4Dozen · Post by **4Dozen** » Sat May 30, 2009 3:52 pm

I have a question for you experts out there. I bought a 73 412 wagon and only the high beams would come on. I took the light cover off just to have a look, I didn’t touch anything and now no headlights will come on. I do get the parking lights, and rear lights to work. I began testing the wires starting at the headlights and get nothing, I tested back to the fuse box and found I was getting no power to fuse 3,4,5,6. My question is where do I go from here. I referenced a wire diagram and found next in-line would be the Dimmer relay. Is this correct? Where would it be located, according to the wire diagram it should be under the fuse box, but in real life I found nothing but metal. I thought I’d throw this up there to hear some expert advice before I start tearing apart the dash. Also, my clock and speedo have never worked, not sure if this could be related. Thanks in advance for any info recieved.

herr_sparky · Post by **herr_sparky** » Sat May 30, 2009 8:35 pm

you mean the speedo needle doesnt move at all? and the ODO doesnt register either? thats a purely mechanical connection, so as long as the cable itself and where it is driven by the front hub is intact/OK then its just unplugged from the back of the gauge cluster. its held in place by a somewhat cheesy plastic nut, and mine seems to come loose now and then.
the clock is powered by its own hot wire, so that can just be unplugged. it sounds to me like someone else "tore into the dash" once upon a time and neglected to re-attach everything, like the speedo nut & clock wire (like i did, once...theres a lot of tiny connections to make without being able to see what youre hands are doing), so even if the source of youre headlight problem isnt actually in there, it might be worth it to make sure everything else is sorted, especially if theres a dangling, unshielded hot lead...

Lars S · Post by **Lars S** » Sun May 31, 2009 10:44 am

Yes 4Dozen the dimmer relay is plugged into the fuse box from the underside, you need to unsnap the fuse box to reach it. Be careful/unplug the battery because it is easy to hit earthed bodyparts with the live fuse holders.

Next in the current chain is the light switch, also a bit tricky to reach.

In the chain is also the ignition switch (check the socket at the steering column which is plugged to the bottom of the ignition switch. You should always have voltage at the red wire and when the ignition is on also on the black/yellow one).

Earthing at the lights themselves is also worth checking.

/Lars S

herr_sparky · Post by **herr_sparky** » Sun May 31, 2009 11:02 am

the fuse box is also susceptible to corrosion for the same reason as the master cylinder(s), so cleaning the fuses themselves and their contacts can help... i bet its a grounding issue, too.

lars: impressive motorbike lineup...T500 and an R69? yes, please...

Lars S · Post by **Lars S** » Sun May 31, 2009 11:15 am

Send you a pm about my bikes Sparky (they fit wery well in my type4 collection; both aircooled and one is a boxer..)

/Lars

4Dozen · Post by **4Dozen** » Sun May 31, 2009 3:18 pm

Thanks all fo rthe great tips, I'll start the search with the info you gave.
I originally thought the speedo was do to the cable. But while I was under there I had a look and thought, maybe, just maby I can kill two brids with one stone...probably not.
I just really needed an experts advice before I create bigger problems. I'll keep you updated throughout my headlight travels. thanks again.

Adam

raygreenwood · Post by **raygreenwood** » Mon Jun 01, 2009 8:50 am

If the act of just working on the lights chanegd something....then you need to check the ground/earth wires that are just underneath the headlights inside of the trunk. There is a wire harness that runs under the trunk mats from sideto side. If memory serves it also has a cround spade and several T-1 style connectors that get knocked loose and corroded,. RAy