Sealed beam?!?

69hurstolds said:

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.

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There's something with most of the composite headlamps with dual bulbs that the low bulb doesn't have a high filament. The H4 is one that does as it is used for both single & dual bulb set ups like the replacement headlight conversion bulb housing out there for our cars. My '96 C/K was one high, one low but the '08, '14 & '15 Silverado's were/are low/high & high. My '81 will also be that way with the Hella conversion bulbs.

Bonnewagon said:

When I look at RockAuto for my actual 1983 Bonneville lights, they are listed as either high or low beam [4651 and 4656]. But I have a 1981 LeMans nose and those are listed as 'high and low beam' [6054]. The wiring is the original Bonneville, I wonder if the 'high/low' bulbs would work with that wiring? Maybe not if the low beam wiring is not there for the two high only bulbs. Maybe I can re-wire with some Firebird sockets I have.

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Bonnewagon said:

So in 'high' the low beam is still a low beam? Why do that I wonder? It would make more sense to be a 'high' and a 'low' so that in 'high' all four would be high beams. Maybe the smart move would be to get some of those 6054 'high and low' bulbs that are actual high beams when enabled and put them in the low beam spots.

I went back to the 4656 that broke and clipped out the actual bulb inside. Both filaments looked identical. So I guess they are really both 'low' otherwise a 'low/high' would be wound differently like an 1157 tail/brake light bulb.

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That 6054 is in error as that's used in '78-'80 LeMans with dual headlights. The '81 header will be the same as your Bonneville's original header. But the out board bulbs will be high beams in "high" with the low beams being off as with the 6054 on the dual headlight cars. Just like what you stated, just like an 1157 bulb would be work.
With the halogen "bulb in a bulb" design the exterior can take some damage or like what you have develop a leak to allow water in & still function.

Bonnewagon said:

So, just to be clear, I can use the 6054 bulbs in my outer spots, and they will be 'low' in low beam mode, but 'high' in high beam mode. Giving me four real high beams in 'high'.

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The 6054 is for dual headlight cars, you'll need to stick with the 4656 for quad headlight cars & it'll give you "low" in low, "high" in high.
The 6054 measures 7.877 x 5.62 in / 200.8 x 142.8 mm.
The 4656 measures 6.6 x 4.23 in / 167.89 x 107.5.

The specs on the H4656 makes it more desirable than the 4652. Reason this works is that the spread of the beam is slightly wider than the 52, and it has slightly more initial candlepower than the 52 in both low and high beam modes. Which you would expect it, since it is a halogen bulb and the bulb reflectors are better designed. I mean, The 52 bulb is based on 1970s technology which is pushing nearly 50 years ago.

Interestingly, low beam bulbs aren't always made the same. A lot of early 4656 low beams, like Wagner's, have 35/35 watts, so it was basically the same brightness in both modes. It depends on the manufacturer. Look for the bulbs that offer "extra vision" or whatever improvement marketing stuff they discuss and look at the specs. For example, Wagner made H4656 with 35/35 watts. Sylvania has an "Xtra vision" H4656, or something like that, that is 35/55 watts. Big difference.

If you want to delve into specifics on federal laws on headlamps, you can make yourself sick from your head spinning while you try to make sense of the federal code:


Basically, there are THREE standardized sealed beam bulb styles that are recommended for the 4-bulb rectangular setup on G-bodies. LED's, composites, and whatever other types notwithstanding. Anything else may not be plug and play, especially the projector beam, whamodyne, weird stuff.

Low Beam
4652 (I think nobody even makes these anymore)
4656 (and I've only seen these in Halogen models)

High Beam
4651 (and I've only seen these in Halogen models)

Found another "mod" you may consider in the low/high beam outside lamps. H4666 has a different prong arrangment, but they fit late 90s S-10s with sealed beam headlamps. These are dual lamp system bulbs that seem to be compatible in size to the H4656/4652. The S-10 has the same type of tan/green/black wiring as the G-body, but it only stops at 2 headlamps. It does not have the extra and separate high beams. Hence the low/high all in one bulb.

Standard Motor Products makes a connector with the correct fitment to the 4666, part number S-686, since it has an angled pin on the back of the bulb to ensure it can't just be plugged into your 4652 connector. You could "de-pin" the original low beam connector and figure out which goes where to make sure, then arrange the wires in the new plug housing and viola! You now have a 45/65W low/high beam that also stays on super bright when your 4651 lights up on high. Keep in mind this is a modification and it likely not a legal one. But if you want to effectively have 4 high beams on at once, here you go. I'd also only do this if I did the relay addition. Not sure how many amps that smaller wire could take. Or if you're handy at terminal placement on these bulbs, perhaps you could de-solder and re-solder the ground terminal to line up with the original plug and swapping the wiring around in the original plug (if it fits). I don't know if that's possible, just thinking out loud.

H4666 pinout.





Connector:









Here's the H4656.