Low Beams vs. High Beams

[OverKnight]

On our 1986 Eagle Limited, when the headlights are turned on, only the right low beam comes on, but when the high beams are turned on, all four bulbs come on.  I'm thinking the highbeam switch, but before we start removing the steering wheel, etc., I thought I'd ask here.  Where would you suggest we start?

Thank you.

[DaemonForce]

If the basic connection only activates your front right low beam, you have a dead low beam circuit in the left side. Take care of that first. When something goes wrong with my lights, every patrolman and their grandma is suddenly out to get me for it. I'm guessing you experience the same thing.

[vangremlin]

The outer lights have both a high beam and a low beam.  So it sounds like your low beam is burned out on the left side.  Time for a new sealed beam unit.

[captspillane]

To be clear, inside the bulb is two distinct elements that are totally independent of each other. I'm guessing that you thought it must be wiring issues because the bulb worked in high and didn't work in low. That just means one element is broken and the other is fine. You'll still have to replace the whole bulb.

[jim]

The connections at the bulbs can corrode beyond repair.  I've had to replace several.  They were available at parts stores.

[OverKnight]

Thank you, everyone.  As Charles Barkley would say, I might be wrong, but I doubt it... 

Four headlight systems have a single filament (either a high or a low beam) in each bulb, while two headlight systems have two filaments (both high and low beams) in each bulb.  None of the Eagle's headlights would have two filaments.  When replacing these bulbs, you'll need either a high-beam or a low-beam.  Again, I might be wrong, but in all of my years of working on cars (more than I care to admit) I've never heard of a dual-filament bulb in a four-headlight system.  If the outer bulbs had both high and low beam filaments, that means you'd have four high beams plus the low beams going when the highs are switched on; I don't think so...

I suspect something is loose or broken in the high beam switch, but since we're planning on replacing all of the headlight bulbs anyway, we'll be able to clean the sockets and rule these out.  Between my job and Joe's classwork, the weekends are pretty much the only time we'll have to work on it, so we'll report back after this weekend.

Thanks again.

[WoodenBirdOfPrey]

Thank you, everyone.  As Charles Barkley would say, I might be wrong, but I doubt it...  

Four headlight systems have a single filament (either a high or a low beam) in each bulb, while two headlight systems have two filaments (both high and low beams) in each bulb.  

Not to sound like a , but you are, in fact, wrong in this case.  Take the headlight out of it and you'll see, the outer bulbs do indeed have a high and a low filament, the inner ones are high only.  Headlight systems are not universally consistent in design across the different makes and models.  And being an AMC owner, you should know by now that AMC isn't a company to do the same thing as everybody else.

[vangremlin]

If the outer bulbs had both high and low beam filaments, that means you'd have four high beams plus the low beams going when the highs are switched on; I don't think so...

The low beam filaments in the outer bulbs turn off when you turn on the high beams, so you only have four high beam filaments in high mode.  The fact that the plugs for the outer lights have three sockets is also evidence of the two filaments.

Hopefully changing out your sealed beam units this weekend will solve your problem.

[WoodenBirdOfPrey]

I wouldn't go as far as to say every 4 bulb system has 2 high/low beam bulbs.  I had an 84 dodge van with the 4x6 sealed beams one over the other.  Upper ones were low beam only and stayed on when the lower (high only) beams came on.  I liked that setup better than the ones on the Eagle, the lighting pattern was better in high because when the brights were on it didn't leave dark/blind spots closer to the vehicle.

And I know we're talking about sealed beams at this point, but i've had 2 newer Chevies with the composite headlights, that actually had separate bulbs and reflectors for low and high beams.  Each of those were single filament bulbs and the lows would stay on with the highs just like my 84 dodge.

[OverKnight]

If I'm wrong, I'll stand corrected.  The pictures of the replacement bulbs I've seen have only two terminals; I don't see how you're going to get a high and low with that.

We'll pull the headlights out on Saturday and find out for sure - thanks again, all.

[IowaEagle]

AFAIK all four light sealed beam systems, round or rectangular the "low beam" light have two elements and the high beam has one.  The Federal DOT requirement that cars use sealed beam units built to specific requirements really messed up US car design until the DOT allowed the use of "modern day" halogen bulbs rather that sealed beams.

Our Eurpean Export Eagles used a headlight housing that looked like a standard sealed beam but in fact had replaceable halogen bulbs

[AMCKen]

If I'm wrong, I'll stand corrected.  The pictures of the replacement bulbs I've seen have only two terminals; I don't see how you're going to get a high and low with that.

We'll pull the headlights out on Saturday and find out for sure - thanks again, all.

If your replacement bulb has only 2 terminals it's the high beam bulb. The outer bulbs should have 3 terminals.

[BenM]

This may help:


These are the basic sealed beam numbers, some are now available in higher wattage.

ID	Dimensions	Elements
1A1 4651	6½x4 165x100mm	High-50w
-	-	-
2A1 4656	6½x4 165x100mm	High-35w Low-35w
-	-	-
2B1 6054	8x5½ 200x142mm	High-65w Low-35w
-	-	-
1C1 5001	5¾ 146mm	High-50w
-	-	-
2C1 5006	5¾ 146mm	High-35w Low-35w
-	-	-
2D1 6006	7" 178mm	High-65w Low-35w
-	-	-
2E1 4666	6½x4 165x100mm	High-65w Low-55w

[carnuck]

Thanks (and an egg) for keeping me from having to dig that up!

[OverKnight]

So what goes good with crow...?

I stand corrected; Joe pulled the headlights out, and as everyone said, the other bulbs have three terminals.  The last car I owned or worked on with a four-bulb system was a 1967 Ford wagon; everything else since has had two bulbs.  A little dated I am, perhaps...

All of the bulbs are halogen, and both of the bulbs on the right side have visible moisture in them.  We're trying to keep the costs down, but I think we'll replace all four; I'd bet the difference between two new bulbs and two old bulbs will be quite noticeable.  One of the headlight adjusters is broken, also, but that's an easy fix.

We've also realized that this car came with fog lights.  The dash switch and the wires with the plugs/sockets are all there.  Probably a ridiculous question, but are stock fog lights available?  There doesn't appear to be much clearance between the holes in the bumper and the grill, meaning fog light housings were pretty shallow; are there after-market lights that would fit?

Thanks again, all.