WARNING! All 257 bulbs are not created equal.

[Wayne K.]

Hello again,

I purchased what I was told was a Wagner 257 bulb as I couldn't locate a GE 257 locally. Before I wrestled with the dash wiring I thought I'd check its operation. I put it in the socket and pulled the headlight switch out and the bulb shined bright but would not blink/flash after leaving on for a minute. The bulb is stamped T257, China. It is not stamped or labeled Wagner. Do I have a poser here or doesn't Wagner stamp/label their bulbs? Does the socket have to be installed in the cluster so it's environment heats up enough that that gets it to blink or should it work as I tested it? If there is a brand of bulb that for sure is a flasher I would like to know so I can order from some internet source.

Wayne

[Jack H.]

Re: WARNING! All 257 bulbs are not created equal.

Look at your wiring/harness... Originals from the era used a SINGLE power wire(typically grey insulation) to an all-metal lamp socket. Interference fit between the metal lamp socket and the dash panel completed the electrical path to ground.

Yes, there have been reports that some 'Made in China' #257 lamps are faulty in terms of blinking. I don't know if Wagner has a contract mfgr supply them with these lamps (#257 'blinker' bulbs are a rather low volume item these days), but ID labeling would rely on the specifics of the contract between Wagner and the foreign mfgr/supplier...

On the bench, simply connecting the lamp between B+ and ground should produce blinking action within 30-60 seconds (takes time for current through the filament to heat it and trigger the bi-metal open/close switching action)

Note B+ in a typical auto environment is NOT 12 VDC! It's closer to 14 VDC since the generator/alternator is running to charge the battery during normal operation. Most auto electric tech benchs are equipped with 13.8 VDC power supplies to mimic 'typical' conditions.

[Wayne K.]

Re: WARNING! All 257 bulbs are not created equal.

Jack,

My 67 has a blue wire coming from the light switch and grey/black to ground. The bulb socket is plastic. The bulb I purchased which is supposed to be a Wagner looks to have more than one filament. I think that a correct bulb is only supposed to have one. Are you saying that the car needs to be running to get the blinker feature to work? Other than the battery in the car and a 12V trickle charger I don't have a source for testing.

Wayne

[Timothy B.]

Re: WARNING! All 257 bulbs are not created equal.

Wayne,

I think the plastic socket is correct because this circuit gets it's groung from the limit switches at the headlight motors. Other bulb sockets in the dash are metal and ground as Jack says. The GE bulbs in my car blink without the engine running so your 257 bulb should heat up and blink with 12 volts.

[Jack H.]

Re: WARNING! All 257 bulbs are not created equal.

In '67, the headlight warning lamp power comes to the lamp on the 18G LBL wire and goes to ground through the through headlight door switches via the 18G GY/DBL/B color coded wire.

The #257 lamp executes its self-flashing function because one leg of the filament in the lamp is a bi-metal contact leaf. This is the same technology that drives your turn signal and emergency flasher.

When cold, current flows causing the bi-metal to heat, bend, and open circuit the load (the lamp goes out). Without current flowing, the bi-metal cools and relaxes to the point it makes contact once more and electric current begins to flow again. Thus, you get blinking with the blink rate dictated by the AMOUNT of current flow through the branch circuit.

Obviously, if either the load resistance of the filament is high OR the driving voltage source is low, you get less branch circuit current flow. This WILL affect the blink rate! In the ultimate case, it's possible to flow a current that's SO LOW the bi-metal never heats sufficiently to cycle open/close....

BUT, these blinking lamps ARE known to flash without the engine running presuming the battery is properly charged. The NCRS Performance verification test is done with the engine stopped AFTER it was started/run with the car not in motion. This is the last leg of 'static' tests performed prior to taking the car on an actual road test. So, NCRS PV judges expect the #257 lamp to blink without the engine running, but after the car was started, engine run, and battery charged for a while.

The PV manual DOES note: "As the flashing function is built into the bulb and heat generated, it will normally take a few seconds for it to warm and begin flashing". In my experience, this is typically a 10-30 second interval. But, remember it's winter now and outside ambient temperature is low.

[Wayne K.]

Re: WARNING! All 257 bulbs are not created equal.

I charged the battery in the car before testing the bulb. The charger indicated battery was fully charged. Car is in winter storeage in my heated garage (55-60 degrees)so I don't care to start it just to check the bulb function. It turned on and off correctly but will not blink. Tonight I'll test the bulb with my trickle charger. If it still doesn't blink I will try to locate a GE 257.

[Clark D.]

Re: WARNING! All 257 bulbs are not created equal.

Wayne, I went through the samething as you. When I had my cluster out I replaced all the bulbs to be proactive. I had to order the 257s from NAPA. Yep, made in China. When all was hooked back up the bulb would not flash. I had the orginal and you can actually see the area at the bottom of the bulb inside the glass that makes and breaks contact. I then looked at the China one, I bought a spare, and found it was a just a regular bulb. I already had the cluster in and I can't get my hands up to the top, so the non flasher is still in the car.

[Wayne K.]

Re: WARNING! All 257 bulbs are not created equal.

Clark,

I found a local parts store that claims to have an older boxed Westinghouse 257 (made in america). Next week I'm going to take the china bulb and compare it to theirs. If it looks different I'm going to give that one a try.

Wayne

[Gary B.]

Where are bulb numbers listed?

Can someone tell me where the bulb numbers are listed for my '66? I've looked in the AIM, but can't find them there. I'm just wondering if I'm at a swap meet and find some vintage bulbs, how do I get a list of what I need without removing bulbs from my instrumental panel, which I don't want to do.

Thanks,

Gary

[Joe L.]

Re: Where are bulb numbers listed?

Gary-----

You definitely won't find them in the AIM. However, they can usually be found in the owners manual or the Chevrolet Service Manual.

[Gary B.]

Thanks Joe; Found them in the '66 User's Manual *NM*

[Terry M.]

Re: Where are bulb numbers listed?

Gary,
If you have the original (8.5 X 11, Corvette Restorer, V16, #1) issue of the NCRS Corvette Specifications Guide, it has bulbs listed for 1953 to 1972. Those charts were not, to the best of my knowledge, re-printed in the pocket Spec Guides.

[Larry M.]

Re: Where are bulb numbers listed?

Gary:

For 1967, this information is shown in the Chevrolet Chassis Service Manual SPECIFICATIONS SECTION (which is at the very end of the service manual), under SECTION 12 BODY AND CHASSIS ELECTRICAL SPECIFICATIONS. Shows lamp usage, candlepower, and bulb number.

I assume that 1966 and other years would be similar.

Larry