replacement bulbs?

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John Mc
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replacement bulbs?

Post by John Mc »

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One of the bulbs burnt out in my front running light/blinker. (I'm totally spacing out on what you call those housings at the moment.)
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As far as I can see, the burnt out bulb is a #1251 (28V and 6.44 watts). I've ordered a 10 pack as a replacement and some spares.

I see there is a similar bulb, #623. It appears to be identical, other than being 28 V, 10.36 Watts.

I'm wondering if that might also be an appropriate replacement, or is the higher wattage likely to cause heat issues in the small, sealed housing?
1951 M37 "Brutus" w/Winch and 251 engine
ashyers
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Re: replacement bulbs?

Post by ashyers »

I don't know if it will bother the housing, but I did manage to melt the cover for the turn signal indicator!
just me
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Re: replacement bulbs?

Post by just me »

If you're wiring is up to snuff, it will be fine in the housing. The current draw is higher, the candlepower is higher (brighter) it will create more heat.
If you're wiring is questionable, the added draw may not be a good thing.
Used in tight quarters or plastic housings/lenses, the heat may cause damage.
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Re: replacement bulbs?

Post by PoW »

If one is using the plastic full round covers (originally fielded on Goats), never fit the larger lamp in the socket that is closer to the lens.

As others have learned, it will melt a hole in the cover.

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John Mc
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Re: replacement bulbs?

Post by John Mc »

Ended up buying a 10-pack of the 1251 bulbs on Amazon for $9. (28V, 6.44 watt) They seem to be working well.

I also ordered two Aero-Lites #303 LED bulbs, just to see how well they work in my truck. I installed one and it's working fine. Might be slightly brighter than the 1251 incandescent bulb. Of course, one of those bulbs cost as much as the 10-pack of the incandescent bulbs.
1951 M37 "Brutus" w/Winch and 251 engine
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Re: replacement bulbs?

Post by Cal_Gary »

Good info John-thanks!
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John Mc
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Re: replacement bulbs?

Post by John Mc »

I'm guessing the info may be old hat to many of you, but I thought I'd share just in case someone was looking. The local Advance Auto Parts had nothing in stock, and did not seem to be able to get the appropriate bulbs.

I've been told that if I replace both front and rear blinkers with LED bulbs, it may cause problems with not flashing correctly. I have not tried it yet. My rear bulbs are still incandescent.
1951 M37 "Brutus" w/Winch and 251 engine
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Re: replacement bulbs?

Post by Rdinatal »

John Mc wrote: Tue May 27, 2025 4:59 am I've been told that if I replace both front and rear blinkers with LED bulbs, it may cause problems with not flashing correctly. I have not tried it yet. My rear bulbs are still incandescent.
Yes, the issue is called "Hyper-Flash". Basically the flasher uses the resistance of the bulbs to work. If one bulb is out, the flasher sequence is real fast. It also helps determine if there is a bulb burnt out.

For LED signal bulbs (no resistance) you will need an LED compatible flasher. I'm not sure the .mil signal units will work.

I was lucky (or unlucky) that both the .mil signal and flasher units were bad. I replaced them with a Signal-Stat switch and LED compatible flasher unit (some rewire required).
1952 M37 - Mods = Locking hubs, battery switch, 2 bank charger, PB, PS, Pertronix SSI, Elect fuel pump w/filter&pressure switch, bikini top, tool box liners, 24v & 12v fused circuits, Seatbelts
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