Headlight blow-out problem!

Jon B

I replaced a burned out headlight bulb two days ago, only to have the "new" bulb burn out within a day. It could be a problem with the old-stock replacement bulb of course, but I wonder if anyone can suggest other possibilities that I might look for, when investigating? Bad socket? Grounded wire? Not sure what "external" things might cause a bulb to go bad.



I have a 6-volt positive ground system with the old prefocus (3-pin flange) bulbs. I installed a dual relay years ago, even grounded each socket to the frame by soldering a separate wire to it.



Both filaments were burned out on the previous bulb; only one is burned out (so far) on the "new" bulb. The inside of the glass (in both new and old bulbs) has a grey fog on it.



A couple years ago I'd installed two new 6-volt halogen bulbs and they worked fine. But in June of 2007, when I turned the light switch on, both bulbs (high and low beams) blew out simultaneously. At that time I suspected some sort of high-voltage surge so replaced the voltage regulator, and put the old style tungsten lamps back in the lights. They worked just fine for the rest of the season, but this spring the tungsten bulb blew, followed (a day later) by its replacement! If this were some sort of voltage surge I'd have expected both tungsten bulbs to blow, just as the halogen bulbs did, so I'm thinking the problem might be in the wiring.



I've posted this over at the AACA tech forum as well. Any suggestions would be appreciated!

Unknown

Jon



Time is usually the culprit in these types of problems. The socket and connection points where the bulb shank and contact points make contact quickly oxidize. The oxidation becomes a resistance in the electrical circuit. As the oxidation continues the resistance reaches a peak point when it isolates the bulb from operation. At times before this occurs the turning on and off of the headlight switch caused the voltage to arc from the contact to the bulb contact and from the socket to the bulb socket case. In your case the switch causes the relay to switch the voltage ... or ground. In all cases the oxidation can be the source of the action. The grey tinge in the bulb case is due to the filiment being consumed as the bulb is being turned on and off. A quick fix for these problems is to use some plumbers helper cloth to burnish the bulb, it's contacts, the socket and the contact there in.



Good Luck.

Jon B

Hmm... Most interesting! Thanks for the thoughts. So, resistance anywhere along the line can cause some sort of voltage change or surge? (I'm not "electrical" still trying to figure out why it feels so strange when I stick a fork into the wall outlet...)



If there is a surge signifcantly above 6 volts, it could explain why the halogen lights blew out. (I get the feeling halogen lights are more "sensitive" to these things, though I could be wrong.)



Where, exactly, would one purcase "plumber's cloth" -- or is this essentially the same as emory paper?



Would abraiding the contacts (to make 'em shine again) remove any protective plating that remains, thus causing them to tarnish even quicker? If so, could one smear some sort of protective coating or grease on the now-shiny contact, to preserve its brightness?

Geoff

The primary cause of bulb blowing is too high a voltage. Have you checked the regulator adjustment? It should be set at 7.25 volts with the engine running with the headlights on.

Jon B

Geoff: ....and this adjustment is within the regulator box? (Remember, I'm the inquisitive but ignorant kid with the metal fork)

mars55

Here is a failure mode that needs to considered. Hudson generators are externally grounded through the regulator. If short to ground on the field wire occurs, the generator will lose regulation and output voltage could rise as high as 30 volts. Although battery will try to clamp the voltage down. You should put a voltmeter across the battery to see what the voltage is.



P.S. The regulator adjustment that Geoff speaks of is indeed inside the regulator box.

[Deleted User]

mars55 wrote:

Here is a failure mode that needs to considered. Hudson generators are externally grounded through the regulator. If short to ground on the field wire occurs, the generator will lose regulation and output voltage could rise as high as 30 volts. Although battery will try to clamp the voltage down. You should put a voltmeter across the battery to see what the voltage is.



P.S. The regulator adjustment that Geoff speaks of is indeed inside the regulator box.

Pos to Neg with the main cables on and the car at idle? Or cables on and car off or car and cables do not matter?

[Deleted User]

Voltage regulation is dependant on the overall resistance of the electrical system being constant. Make sure that the ground cables from the battery to the frame have clean connections and minimum resistance... also if there are other grounds... such as the generator that they are in-place and with minimum to 0 ohms of resistance. E= IR or voltage is equal to the current times the resistance. In other words to regulate the voltage a constant current is passed through a fixed resistance. The regulator acts as a current valve. If the constant resistance becomes unstable the circuit where that resistance resides will fail. Not withstanding that high voltage is usually the cause of failed lamps... a unstable resistance will create a mystery failure ... one can not seem to find.

mars55

Pacemaker500 wrote:

Pos to Neg with the main cables on and the car at idle? Or cables on and car off or car and cables do not matter?

The test should be done with the voltmeter connected to the Positive and Negative terminals of the battery and car at idle and then at a engine speed of about 30 MPH. The voltage readings should constant to one decimal place if using a digital meter. The idle reading can be lower and the readings can slowly increase over time providing they do not exceed 7.8 volts.

Geoff

I agree that there could be a destructive failure if the chassis connection to the battery was unstable. A momentary open circuit here could lead to up to 30 volts spiking through the system. However, I imagine a bad earth would show up first in starting problems.

Geoff.

[Deleted User]

mars55 wrote:

The test should be done with the voltmeter connected to the Positive and Negative terminals of the battery and car at idle and then at a engine speed of about 30 MPH. The voltage readings should constant to one decimal place if using a digital meter. The idle reading can be lower and the readings can slowly increase over time providing they do not exceed 7.8 volts.

Thank you. Testing procedure now added to ever growing Hudson Manual of Additional Mechanical Procedures, Diagnostics, Operational Guidance and Repair Tips.

SuperDave

Jon,

If all the voltage readings come up "OK" you may just have some leaky old stock bulbs. I went through at least a half dozen "Old stock" bulbs on my Model A Ford before I finally bought some new replacements. The bulbs sometimes loose the hermetic seal and the filaments will burn out rapidly. Nothing like being in the dark.. LOL

Jon B

A friend has suggested installing an .05mfd capacitor in the line between the headlight relay and the headlight bulb (actually, one capacitor each, for the high and low beam circuits). This, he says, would absorb any "transients" (momentary blips or spikes of electricity, as I would understand it) that might be causing all these lamp blowouts I've been experiencing.



Has anyone ever attempted such a "fix" for electrical problems on their Hudson? Does it sound reasonable in theory?

Unknown

In theory, the cap should work. Think of them as little filter reservoirs for electrical energy. Whether or not it will help in your case is something that time will tell. We used caps of much greater value to eliminate pops in car stereos back in the 70's. The pops usually occured when power was intermittently drawn (ie; brake lights or AC cycling) while the stereo was on. We placed them in the feed to the stereos.