1973 CS Headlights Stopped working
- Thread starter inmantua1
- Start date
Honolulu
Well-Known Member
step by step
You want to follow the current track from the lights back to the battery. It would be nice to have a wiring diagram handy, there should be one on this site. I assume you have no other untoward electrical symptoms and thus the problem(s) are confined to your headlight circuits, and that your headlights are stock and unmolested.
first thing I'd check is whether the lights are getting power or not - remove the socket at the back of the bulb and use a continuity tester or VOM. Check that the bulbs are not burnt out (unlikely they'd both go at once) and that the ground is functional. IIRC the ground is on the front panel, follow the thick brown wire to where it is screwed onto the body.
Next, are the relays operating (do you know how relays work?) There are two "signal side" connections and two "power side" connections. Relays must be grounded, BMW always uses a brown wire as ground, make sure it actually grounds. Terminals on Bosch relays are numbered 85, 86, 87 and 30. Once in a while there is another terminal but it's just an added connection for one of the original four. Two relay terminals operate a solenoid, which connects the other two. Power one of the signal side terminals and when you ground the other, the relay should make an audible click, and at the same time you'll have continuity between the two "power" connections. Sorry I don't remember which are which, but on some relays the schematic is engraved on the item.
You want to follow the current track from the lights back to the battery. It would be nice to have a wiring diagram handy, there should be one on this site. I assume you have no other untoward electrical symptoms and thus the problem(s) are confined to your headlight circuits, and that your headlights are stock and unmolested.
first thing I'd check is whether the lights are getting power or not - remove the socket at the back of the bulb and use a continuity tester or VOM. Check that the bulbs are not burnt out (unlikely they'd both go at once) and that the ground is functional. IIRC the ground is on the front panel, follow the thick brown wire to where it is screwed onto the body.
Next, are the relays operating (do you know how relays work?) There are two "signal side" connections and two "power side" connections. Relays must be grounded, BMW always uses a brown wire as ground, make sure it actually grounds. Terminals on Bosch relays are numbered 85, 86, 87 and 30. Once in a while there is another terminal but it's just an added connection for one of the original four. Two relay terminals operate a solenoid, which connects the other two. Power one of the signal side terminals and when you ground the other, the relay should make an audible click, and at the same time you'll have continuity between the two "power" connections. Sorry I don't remember which are which, but on some relays the schematic is engraved on the item.
You don't have a fuse for the headlights, only a high beam relay as well. Power comes from ignition switch to "unprotected" side of fuse block at # 6 and #7 and then goes to main light switch and then to the dip switch. After that it travels down the steering column to the headlights. It may be the dip switch that is the culprit, wiggle it, just hope that you don't have fried wires from there to the lights. Pretty scary wiring arrangement for its day! `74 models got fuses, the Blue Book refers to it as "from 1973 models on."
As Chris properly notes- there is no low beam relay. Don't waste your time looking for it unless your car has been upgraded from stock.
Also- "BMW always uses a brown wire as ground" is not correct.
Also- "BMW always uses a brown wire as ground" is not correct.
echappe
Well-Known Member
I recently had the same problem in my 2002, a wire underneath the relays had frayed. This was found after the headlight switch and dimmer switch had been replaced and headlights still not working
No lights, no camera, no action...
Let's try again:
No lights at all? No low, high, turn/run, etc.
When the dip switch or high beam switch is activated- no lights?
Sometime 73 on, there was a load sheading relay wired with the heater. No heater blower action? If your car does have this relay, it above the fuse box and it's the right one of three.
I'd first probe with a meter or test light the main switch wires to see if there's juice there.
Let's try again:
No lights at all? No low, high, turn/run, etc.
When the dip switch or high beam switch is activated- no lights?
Sometime 73 on, there was a load sheading relay wired with the heater. No heater blower action? If your car does have this relay, it above the fuse box and it's the right one of three.
I'd first probe with a meter or test light the main switch wires to see if there's juice there.