It never ends......

'75 Cutlass Salon--So I am getting the Cutlass ready for Japanese inspection in the morning. I washed under the hood and underbody because they will fail you for as little as some oily grime underneath. Afterwards my headlights quit working. Here is where I stand:

Everything else still works from what I can tell. Parking lights, turn signals, instrument cluster lights, engine runs fine, and interior lights all work as they should. When I pull the switch all the way out, the lights don't come on, and the high beam indicator stays on, even if I flip between highs and lows. I checked the connector at the lights and all 3 prongs have power and no ground when switched "on." I have followed the wires back from the lights to the firewall connector and there are no shorts or cuts or anything. They aren't even wet, even at the connector. I avoided that.

So any ideas why I would be getting 12v to all three wires of the headlight connector when I switch them on? I know one needs to be a ground obviously. Which one should be ground? I have a FSM with a wiring diagram, but it isn't helping me.

Thanks in advance! T-minus 9 hrs and counting until inspection!

 

Unplug both headlights, then use a test light or meter to check for voltage at each of the colored wires on each plug (Black is the ground, if I recall).
Also check to be sure there is no resistance to ground through the ground wire.

You can also check each bulb by clipping a ground wire to the ground terminal, and touching a 12V wire from the battery to each of the other two terminals - one is high beam, one is low beam.

If you have no voltage at a high or low beam wire on both sides, check the high beam switch.
If you have no voltage at only one side, check your wires and connections.

Also might not hurt to release the metal terminals from the plastic connector plugs and give them a good shot with a wire brush.

- Eric

 

Thanks for the input. Unfortunately I'm getting 12v to all three wires at both headlights when I turn the switch on. No ground, all 3 hot. I'm leaning towards thinking either water is indeed in somewhere shorting it out (like maybe the dry looking connector on the firewall?) or the headlight switch is bad. Wires are light green, blue, and tan FWIW.

 

Are the headlights connected when you are testing the wires?
They have to be unplugged to test them.
And you have to check continuity to ground.

edit:
Interesting - I just consulted the '75 CSM and your headlights are wired backwards.
The Light Blue is the hot, and is ALSO the common, while the green and the tan are ground returns through the dimmer switch.

SO... When you turn on the headlight switch, power flows from the switch through the Light Blue wire to both headlights, through one filament in each (either the high or the low beam), then through the respective wire (either green or tan) to the dimmer switch, where it is connected to ground.

It sounds like you have a bad ground, so in your case, that means you have to check the dimmer switch on the floor, and the wires that connect to it.

- Eric

 

Roger that. It just started pouring rain so I guess I'll be waking up extra early to troubleshoot. I will see what I get with both pugs disconnected from the headlights.

Also, just to make this even more complicated, I don't have a floor dimmer switch. I guess it's a Salon thing, but the dimmer is integrated into the cruise control stalk on the column.

 

Oh. I have no idea, then. I know nothing about those.

Maybe the G-body guys can help.

- Eric

 

Good Luck with the Inspector's I know they can be tough for sure. Lived in Tokyo for 17 years. Are you stationed at Kadena? I lives 5 min from Yakota Air Base on the main land. Anyways, Good luck!! interested to hear what the inspector says.

 

Just for your information, on a 12V DC electrical system, as on most cars, power flows out of the batteries negative side, and returns through the positive terminal when the circuit is complete.

 

Yes, Mr. Physics Professor.

Electrons are negative, and so flow away from the negative and toward the positive pole.

But, conceptually, most people look at it the opposite way, and it makes no difference functionally.

- Eric

 

Hmmm, late to the party as always....but here's my 2¢. IF the headlights were working fine before you pressure washed under the hood? Get your compressor out and blow dry every connector you can see. Then add a small bit of dialetric grease to the connector to prevent this problem in the future. It may work, and it may not. But the odds are if everything was dry prior and all lights worked, it should work just fine after it's all dried out again.

Eric, I believe they started putting the headlight dimmer up in the stalk around 73 or 74. Same basic principle as the foot switch, just different location. The wire leads will be on the column connector.

 

Column mounted dimmer was part of the Salon package starting 73. GrandAMs and possibly Lagunas also had it. Think it was 78 or 79 when GM went to column dimmers on all passenger cars.

A Salon dimmer switch functions pretty much the same as a floor-mounted switch, just in a different location. Pull the turn signal lever and a metal rod runs down the column to the actual switch. It does the same thing as you pressing the floor switch with yer foot.

GM stuck to that design for years, long after everyone else had gone to switches that changed ground path for the different filaments and incorporated "flash-to-pass".

If the problem started after you washed underhood, it is definitely water-related. You just have to find out where the water got in the wiring.

If they'll fail you for a light oil film, nothing I own would pass a Japanese inspection!

 

I doubt they would have failed MacArthur.

- Eric

 

Tested the plugs disconnected from the lights. With the switch in the on position, the light blue wire has 12v, the other two are grounded. With the lights "off," all 3 have ground.

 

I don't see where you answered Eric's question of testing the lamps with direct battery power . So try that....or Try testing the continuity of each lamp for shorts (without harness connected of course) on an Ohm meter... maybe the lamps filaments are shorted and that's why your getting the 'high' beam lamp all the time. Maybe they 'used' to be sealed beams...! Good luck

 

So you're saying that BOTH the tan and the green go to ground?
Only one should go to ground at any given time.
The problem could be your dimmer switch.
Confirm good continuity by connecting a single filament of the headlight bulb to the blue and the green, and then to the blue and the tan, and then work back from there. When connected to the right terminals with the switch on, the headlight should be bright when the dimmer switch is in the right position.

- Eric

 

I would suggest trying the test again with the high beams on and see what the results are for 12V and ground.

 

I've ordered a new headlight switch and dimmer switch, but they won't be here for a week or two. In desperation yesterday I just wired up a ghetto-fabulous harness with a couple relays to make the lights work. That part passed, but I failed for other ridiculously stupid things. Back again today after some more fixing. After I pass, I'm going to trouble shoot a little more while I'm waiting on the new switches to show up and I'll report back with the results. Thanks a ton for all the quick help guys!

 

Yup---well, I work for Kadena, but I actually work at Naha Airport, and I live down by Kinser. And yes, the inspectors are being real ball busters as usual. I have pretty slick custom combination reverse light and turn signals to meet the amber turn signal requirement. They said I couldn't combine the two housings because it might confuse somebody. REALLY? Because I use my turn signals while I'm backing up ALL the time, and even if I did, you think people couldn't figure it out? They were going so far as to measure my back seat saying it was too big for what was listed on my title as a 4 passenger car, and I might have to add another seatbelt and call it a 5 passenger car. These dudes are seriously a$$holes.

 

You're welcome - we try.

- Eric

 

Haha... They need to remember this is an American car. Most of us Americans have wider behinds!

Good luck on the rest of the inspection. Cruise control should pass with flying colors...

 

Hate to say this, but unless there's a really unusual back seat in that thing, it IS a five-passenger car.

Are you sure there isn't a center seat belt buried under the back seat cushion?

- Eric

 

Every 1975 Cutlass built came from the factory with three sets of seatbelts in the back.

 

Tell the inspector to go work for the nuclear plant. They need a good QC guy over there.

 

So, it's been a busy week or two. Long story short, I finally got it past inspection (after 3 days of trying). Funny interlude, immediately after passing, I drove around front, updated my paperwork, jumped back in all excited, and it wouldn't start lol. At least it waited one more time to die instead of crapping out in the line right after they told me I passed. They no kidding probably would have taken my paperwork right back! Anyways, you can read that saga here if you are interested....

http://www.73-77olds.com/forums/showthread.php?t=9760

So, back to the headlights, I received my new dimmer switch and headlight switch. I replaced the dimmer switch and you guys were right. That was it. Now to figure out how to route the wire back through the cover on the steering column. It's just plugged in and tucked back up in the dash for now (and I can't remember the last time I used high beams here on Okinawa).

Thanks for all the help!

 

You're welcome.

Glad they finally passed you!

- Eric