67 headlight warning flasher revisited

[Wayne K.]

This weekend I managed to get up behind the dash to try and figure out why my headlight warning lamp is not working. After wrestling my way to the correct socket ( this stuff was a lot easier to do 40 years ago ) here is what I found:

The bulb looked good but it was a T1895 not the 257. I checked the specs on the 1895 and they are the same as a 257 (14v .27amp). I used my multimeter to check it for continuity(one probe on end that contacts the grey/black wire and the other to the metal side of bulb that contacts the socket attached to the blue wire) and got a reading so thinking the bulb is good.

With the headlights turned off no power to either blue or grey/black wires at bulb socket. Headlights on I have power to the blue wire and the grey/black when the bulb is in the socket but when I remove the bulb my test lamp only comes on off the blue wire.

The bulb socket looks fine and I cleaned it up with some electrical contact cleaner. What am I missing here?

[John H.]

Re: 67 headlight warning flasher revisited

Wayne -

Those are the results I'd expect to see for the circuit. Is the bulb not illuminating, or not flashing, or ??

[John H.]

Re: 67 headlight warning - Add-On

Is the T-1895 bulb a flashing bulb?

[Wayne K.]

Re: 67 headlight warning - Add-On

John,

Thanks again for the reply. With bulb installed in the socket it does nothing. Unless I was bench testing it incorrectly the bulb did show continuity and it looked to be OK. I don't believe it is a flashing bulb. I'm including a link to the 1895 bulbs specs. Are all 257 bulbs regardless of mfg. flashing? Do you think if I simply locate and install a 257 I'll be in business? I was surprised that my test light came on probing the grey/black terminal. Is that not the gound wire? The other day when I tested the grey/black wire at the limit switch with light switch on and headlights down the test light didn't come on. At the lamp socket it does come on probing the grey/black.

http://www.donsbulbs.com/cgi-bin/r/b.pl/1895~usa.html

[Larry M.]

Re: 67 headlight warning flasher revisited

According to the 1967 Chevrolet Chassis Service Manual the correct bulb for the Headlamp Motor Warning is a #257, which is a flashing bulb. It is 2 candlepower.

The Brake Alarm Lamp bulb is a #1816, which is non-flashing and is 3 candlepower.

A #1895 bulb is shown for Brake Alarm Lamp for Chevelle and Chevy II. It is non-flashing and is 2 candlepower. This bulb is also used for other, various dash and instrument lighting for Chevelle, Chevy II, and Camaro....but not for Corvette.

I would check your bulb(s) on the bench using a 12 volt battery to be sure they light and flash correctly before re-instaling. If they work on the bench, they should work in the dash, and your problem is from another source.

Larry

[Gerard F.]

Re: 67 headlight warning - Add-On

Wayne,

The blue wire at the headlight warning socket is the hot wire fed from the light switch. The gray black is the ground wire which goes through both limit switches. When both headlights are fully open, the circuit is open and there is no ground for the bulb.

If one headlight is not fully open and the headlights are on, the circuit is grounded and the bulb will will light.

The flasher mechanism is within the 257, as it heats up it begins to flash on a little faster. When cold, it flashes very slow.

I think if you put a good 257 in the socket and you are hot on the blue wire, it should work and flash. Otherwise you will need to chase down the ground through the gray/black wire and limit switches.

How do I know this, I got dinged on this very item of having the wrong bulb in the warning light socket on my 67.

Jerry Fuccillo
#42179

[Joe R.]

Re: 67 headlight warning flasher revisited

Hi Wayne:

I wrestled with this circuit a couple years ago and was familiar with the details then, but it has been a while.

As I recall, the bulb socket is an insulated plastic socket with two wires. For the bulb to light, you need 12 volts *across* the two wires. So, try connecting your test light across the two wires with no bulb in the socket and see if your test light illuminates. I suspect that it won't.

From your description, it sounds to me that power is available to the bulb on the blue wire, but the ground return on the gray wire is not connected to ground.

I believe that the limit switches on the headlights are wired in parallel to connect the gray wire to ground if EITHER headlight is not fully raised. So, if your wiring is intact, one thing that could cause the gray wire to remain ungrounded is if BOTH limit switches are defective. This may seem implausible, but as I recall that turned out to be the problem with my car.

To check this theory you could remove the two connections to one of the limit switches and short them together. If the indicator bulb lights when you do that (with the headlights on), the problem is with the switch. Note that you only need to do this on one limit switch to test the theory, since the two switches are connected in parallel.

By the way, if you end up replacing a limit switch, be very careful getting the two retention screws out. One of mine was frozen and it broke off during removal. That created a whole new headache that I didn't need.

[Richard M.]

Re: 67 headlight warning flasher revisited

Guys.....a side question? Our '63 "Lights" indicator always flashes when the buckets are open in the full up position. Never on when partially open or when down with headlights powered on as I'd expect. Seems totaly backwards. I'm getting ready to squeeze my hands in there today and look.

Thoughts? I always get this uncomfortable feeling when I stick my hands in the hood "scissors" opening and would like to minimize time in there.

Thanks,
Rich

[Wayne K.]

Thank you all for the advice. I'm going...

to do some more investigating. From what I've been told here I think I may have a grounding issue. I did remove both limit switches and checked them for continuity. With the plunger pushed in they both broke continuity which is the way I think it should be. I will also try and secure a 257 bulb although the specs on a 1895 are the same except for the flashing feature. With the 1895 in place the test light came on probing either the blue or grey/black wires but the bulb was not functioning. I bench tested the bulb using a 12 volt source and it did come on. I will respond after doing some more exploring.

[Wayne K.]

Re: 67 headlight warning flasher revisited

Rich,

I can't answer why your system seems to be working opposite of how it should but I can advise you to please put a bolt through the safety hole of the hood support so we don't have to hear about you getting injured.

Wayne

[Joe R.]

Re: Thank you all for the advice. I'm going...

Hi Wayne:

The current 257 bulbs that you get from the Corvette restoration suppliers are typically made in China and do not always flash reliably. I was able to buy a genuine GE 257 at my local NAPA store. The box was obviously very old stock, but they had them.

In terms of simply testing your wiring, I think that just about any bulb with the standard socket would work. You could try swapping in a known-good bulb from the several that are used for general illumination of the dash cluster.

[Timothy B.]

Re: 67 headlight warning flasher revisited

Rich,

I think I would start by disconnecting the headlight harness ground wire at the core support. This wire is the common ground for headlamp,parking and limit switches. After that, unhook the black/white wire off both limit switches and hook a test wire from both the limit switches where the black/white wire plugs to them to a new ground. If the tele tale bulb starts working properly then there is a problem with either the headlamp wiring or the marker light wiring sockets. All these share the same ground wire so what you are doing is eliminating the other sockets and headlamp motors.

It's all a process of elimination and others may have a better suggestion but the limit switches are normally closed so power is getting to that socket from somewhere.

[Richard M.]

Re: 67 headlight warning flasher revisited

Timothy, Thanks I'm in there right now....rich