what size light bulbs

[Fire_junky]

Anyone know what size the origanal dashlight bulbs where? What size or part number. All mine where blown when I bought the car so I was waundering if the size that was in there was wrong. They say 12v 3.4w

[MikeW]

The factory service manual for my '72 lists 3W. Keep in mind that it really doesn't matter what the wattage is. A 4W bulb will be brighter than a 3W bulb and a 3W bulb will be brighter than a 1W bulb. Unlike a fuse, putting in a smaller unit will not cause it to burn out any sooner. In fact, lower wattage bulbs tend to last longer since they don't get as hot.

I'd verify that your bulbs are, in fact, no good. You may just have a blown fuse or a wiring problem.

[Bambikiller240]

If they are all blown, most likely cause is butchered wiring and resultant short.

[MikeW]

If they are all blown, most likely cause is butchered wiring and resultant short.

I don't think it's possible to burn out a bulb with butchered wiring. You can take a 3W instrument bulb and wire it directly across your car's battery and it will simply light up. Take a solid wire, a wrench, or a screwdriver and run it directly across the battery and things will get exciting real quick. The bulbs operate a 12V and unless the voltage was significantly higher I don't think there'd be any problem.

[jimbo99]

For my 260 went through the samething chopped wiring was the problem but, to answer your question the 3898 bulbs I got from the WWW.TOPBULB.COM web site, great service sent them the specs and a picture $1.00 each + shipping very quick. The SAE type bulbs I got NAPA parts store

Seat Belt Warning 1.5 Mini-Bayonet Type OSRAM 3898 12V 2W

Defogger Switch 1.5 Mini-Bayonet Type OSRAM 3898 12V 2W

Hazard switch 1.5 Mini-Bayonet Type OSRAM 3898 12V 2W

Defogger warning 1.5 Mini-Bayonet Type OSRAM 3898 12V 2W

Choke warning 1.5 Mini-Bayonet Type OSRAM 3898 12V 2W

SAE

Speedometer Illumination 3.4W 57 2

Brake Warning Lamp 3.4W 57 1

High Beam Warning Lamp 3.4W 57 1

Tach Illumination 3.4W 57 2

T/S Lamp 3.4W 57 2

OIL-TEMP Illumination 3.4W 57 1

AMP-FUEL Illumination 3.4W 57 1

CLOCK Illumination 3.4W 57 1

Jim

[EScanlon]

Use Sylvania #53(BP). These are a direct exchange for the ones in the car, I've heard that GE 1445 also works, but I can't confirm that as I used the Sylvania's.

The BP denotes the "Bayonet Plug" afaik. The SKU Code from the back of the package is: 0 46135 33721 5

The leading 0 and trailing 5 are those very small numbers to the right and left of the SKU Bar lines. So omitting those (for different POS Scanner systems) the SKU would be : 46135 33721

I include it both ways, because it depends on your store having those numbers in their database (AFAIK).

I installed these in my car and I am well pleased with the amount and adjustability of the light. The bulbs are bright enough that just one in the center gauge is enough to light up the face. (Granted, I had also repainted the inside of my cases with a Polar White paint.) As far as adjustability, the dimmer has them lit completely through their range without any significant flutter to the light given.

But I agree, first do ONE bulb, and check, THEN go on to doing the others. It may be as simple as a fuse, or even a pulled ground.

2¢

Enrique

[Bambikiller240]

By butchering a wiring harness I mean modifying it (intentionally or unintentionally) so that more current (amps) flows through a cetain path than that path was designed to carry. Ever accidently short something out and some item in the circuit "pops". That's what I'm refering to.

AFAIK, it's the amperage travelling through that will cook the bulbs. Just like Headlamps that draw more current than stock headlamps can cause the wiring to fail. The filiment will fail before the wiring in this case.

I am certainly no expert on electrics, but I doubt that a 3W bulb cannot be made to fail by running excessive amperage through it.

[MikeW]

I am certainly no expert on electrics, but I doubt that a 3W bulb cannot be made to fail by running excessive amperage through it.

You can't run excessive amperage through a bulb. That was my point and the reason I gave the example of hooking a bulb directly to your battery. To demonstrate, I just ran the red side of a jumper cable to one post on the battery and hooked the other red side to a 3W instrument panel bulb. Finally I touched the base of the bulb to the other battery post. Don't try this at home, kids. A slight slip and I'd have had an extreme amount of amperage flowing. In fact, I did slip briefly and created a nice little pit in the battery post cable; you can see it in the attached picture.

[Bambikiller240]

Mike: Then why do fuses blow when excess amperage flows through them?

I inderstand that the bulb all by itself won't draw more amps, but if something else (for instance a Fan) were to be powered through the circuit that lights the bulb, couldn't the amp draw from the fan try to pull enough current through the filiment to cause it to fail?

[MikeW]

Mike: Then why do fuses blow when excess amperage flows through them?

Because the fuse has less resistance than the bulb. A fuse will allow enough amperage to flow to melt the fuse. A fuse is always wired in series with something else that has greater resistance than the fuse itself: headlights, the blower motor, etc. If a short circuit occurs between the fuse and the device it's protecting the resistance will be gone so more amperage will flow and the fuse will blow - thus protecting your wiring. If there was no fuse enough amperage would flow to melt the wire at the point of its greatest resistance, perhaps at a connector somewhere in the harness. In my case, with the jumper cable, the point of greatest resistance was where the clamp brushed the terminal so that's where things started to melt.

[MikeW]

I inderstand that the bulb all by itself won't draw more amps, but if something else (for instance a Fan) were to be powered through the circuit that lights the bulb, couldn't the amp draw from the fan try to pull enough current through the filiment to cause it to fail?

No, in this case the bulb would be limiting the current flow and the fan wouldn't even begin to run. So little current would be flowing that the fan would be the equivalent of a straight wire. The bulb would still light up just fine ...

[Bambikiller240]

If a short circuit occurs between the fuse and the device it's protecting the resistance will be gone so more amperage will flow and the fuse will blow - thus protecting your wiring.

So, couldn't "butchered" wiring cause something like this to occur? Where the filiment in the bulb would act like the fuse?

The one example that comes to mind is the S/S Clutch hose on blitzcraig's car that kept melting and burning due to grounding issues.