Sealed beam?!?

There must be a top gap in the sealant used to bond the glass housing & outer lense. Only an issue with halogen bulbs. AS for those screws, all the fefreshed buckets for both cars got stainless screws as part of the refreshing cause those plain steel ones were a bad bean counter's idea.

Bonnewagon said:

While going through my stash of bulbs, I set a likely looking one on the work bench. When I went to pick it up later, the whole front lens fell off! It was like the bulb was made of two parts glued together and it failed. I had no idea that was how they are made. That would explain the water getting inside. And yet with that much water, both beams still worked.

The bulbs seem to be pretty available. Any advice on the 'extra bright' versions? LED versions are $100?!?

Another thing- I see 'low', 'high' and 'low/high' one for sale. Aren't all the three prong bulbs 'low/high' ?

Click to expand...

Had the same thing happen to one I had on the shelf. Unfortunately the lense hit the floor and broke.

Not going to insult your intelligence here, but only providing extra info for those who may not know about the G-body quad headlamp affairs.

If you got the rectangular 4 x 6, the three prong is technically a low beam/high beam, aka 4652, or GM p/n 5966200 from the factory. But they usually just call them low beams, notated as "2A" on the bulb. High beams are notated as a 1A on the bulb (non-halogen were 4651, or GM p/n 5966201, halogens were H4651, or GM p/n 5930567).

"Low beams" are three prongs. Tan wire to low beam, green wire to high beam which jumpers over to the high beam bulb, and a black ground. G-cars are set up that the low beams go off during the high beam operation, but get power through the high beam circuit, thus all 4 are headlights light up. They do this because they have a spare lamp circuit that comes on (green wire) when the bright lights are on. The high beam selector switch in the column takes power away from the tan wire (low beam only) and provides power through the green wire to the spare element in the low beam bulb and the high beam at the same time. There are other cars that have the low beams go off when the high beams are on. (I believe the 87/88 is like this, but I can't recall) So in reality, there's 2 elements in the low beam bulb, the low circuit and high circuit. This is why sometimes when only ONE element goes out on a low-beam bulb, it can light up in the other mode. It can mess with your head if you don't know about that 2nd low beam circuit.

Age can have an affect on the old style headlamps. Especially if the glue doesn't hold and they get fogged. However, the way the lenses are cut and the reflectors make the difference most of the time.

Oh, H4656 works too as the replacement for 4652. Forgot about that. AFAIK, the H4656 is a halogen low beam. I don't know if they ever came in a "regular" lamp, only halogens I've seen.

BTW, the 1A and 2A designators isn't the number of filaments. It's the classification of maximum candlepower output. Forget what those limits are, but that's what it's for.

One thing that lots of people do is have the low/high beam circuits run relays to power 12V directly from the battery to the headlights. This puts FULL 12V (nominal) to the lamps instead of having to run through teeny little wiring to get maximum brightness. Lots of ways to wire those relays up, btw.

Here's just ONE example from a Chevy Truck forum. Other than the shape of the bulb, it would be exactly how the G-bodies are setup. It shows one way how you can get full power to your headlamps with only two cube relays and a bit of battery positive wiring and some ground wiring. You still want to run an inline fuse as well for the battery wire, just in case. Of course, if you want it to look factory, you're going to have to get creative to hide it.

You would think 1A would be less but no. 1A is higher candlepower output than a 2A bulb. AFAIK, there isn’t any other designator like 3 or something.

I’m not an electrical engineer so I have no idea why they made the bulb circuits the way they did. Maybe the fact that 4 x 6 bulbs are kinda small, along with many other 4 lamp systems, but look at a 93-97 Camaro if you want to see tiny headlights.