Possible culprits behind intermittent headlight loss?

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Have a '66 Fairlane wagon, the headlights will blank out after maybe 15 - 20 minutes on low beam. Turning the switch off for a few secs and then turning on will typically get them back on temporarily but
they'll continue to go out. Further, hitting the hi beams is almost guaranteed to kill the lights. Replaced the switch and the floor dimmer, neither cures the problem.
Any suggestions as to where to begin looking?
Thanks.
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I have a similar problem with the radio, turn it on, plays for about 10 sec then goes away. Thouth it was a bad fuse, some will do that. But that did not fix it.
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On my 64 T-bird I found some of the crimps in the fuse block were no longer tight and had to solder them.
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What are you running for headlights or other lights hooked to "that" circuit? The headlight switch contains a circuit breaker for the headlight circuits only and your concern indicates high current flow in the system

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Don't most older cars have self resetting breakers for the headlight circuit/s? Seems I remember them ocassionly cycling on and off...
Do you have a factory shop manual for it? If not, google up "Faxon Auto Literature". They more than likely have one in stock.
Good Luck!
Erik
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Doc wrote:

Its a worn circuit breaker contained IN the headlight switch. The usual fix is to replace the switch with a new one. Go one step further after that and install headlight relays to take almost the entire load off the switch, and the headlight switch will outlast the car. Much brighter lights, too.
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Thanks - can you advise more details on this - what's involved, where to find the pieces etc.
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Sharon Cooke wrote:

The headlight switch is a standard auto parts place item, even for a 40+ year old Ford. The relay is available there also, or you can buy a pre-wired harness from someplace like www.autodynamic.com that simply plugs in.
You can get the relay info by typing headlight relays into your browser search engine.
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Did you inspect the female terminals' tension at the dimmer switch harness? Are they corroded or clean? Other than that, you most likely have high resistance somewhere common to both bulbs. This could be a poor ground, splice, fuse holder, etc. in the system.
I don't know what kind of fuse protection is used on your Fairlane, but *if* it uses a circuit breaker, the breaker could be faulty, or the contacts between the fuse box and breaker could be loose which would heat up the breaker and trip it thermally.
Toyota MDT in MO
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On the old cars, (especially fords), it was usually a bad headlight switch.
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Doc wrote:

I see that happen to old vehicle when folks try to run halogen bulbs in them without adding a power relay.
The bimetal circuit breakers in the old switches cannot take the amp draw the modern halogen bulbs draw.
The old time conversion kits that were sold when halogens first came out are a simple Bosch relay that is fused to the battery and wired so the switch is just the trigger for the relay.
Here is a site on how to wire one in. http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm
The other reason I see the breaker cook is a bad connection in the plug for the headlight switch. The main power wire's spade connector can get ratty which will cause arcs and heat and breaker failure.
I see this same bad connection on the floor dimmer switch plugs.
And last, a bad ground can cause heat issues. I would verify the headlight ground tags and the body's main ground from the battery.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id !15147590 (More Off Road album links at bottom of the view page)
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wrote:

There is almost no difference in the current draw between the old bulbs and halogen.

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Ashton Crusher wrote:

There is enough difference to blow the bimetal circuit breaker, especially when the high beams kick in. There is a 'reason' we needed the conversion kits, every one I have seen without it has sooner than later cooked the switch.
Some kits (one for my 1970 Pontiac Safari Wagon) even wired the relay in parallel with the light switch circuit so the headlights got two power sources which was enough to keep that bimetal switch cool.

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wrote:

There was a long discussion of this in a T-bird group. With the headlights from 66 bird what was measured...
with a battery charge of 12.6 static volts... "Old" style headlamp.... low beam: 2.2A. @12.18V,......... high beam:4.2A. @12.07V. "Halogen" headlamp.... low beam:3.0A.@...,.......... high beam:4.1A.@.... So the maximum draw with the halogens was actually LESS then with the old style bulbs. Not really surprising since one of the benefits of the halogen bulbs was that they are more efficient so for the same legal max output they actually draw LESS current. The newer bulbs had brighter low beams, that's why the low beam current was higher, but still less then on high beams which is the max current draw when all four bulbs are lit up.

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Ashton Crusher wrote:

Real life says someone is playing fast and loose with the numbers!
Got any 'real' numbers for the watts of the bulbs, not something someone made up with who know what kind of skill or meter?
Once again I will say 'every' old vehicle I have seen with halogens that were not included stock burns up the headlight switch unless the conversion kit or a relay is used!
I see this 'lots' due to being a wiring tech for a owner owned fleet of old vans on one 9 year contract and all the old Jeeps I play with and repair.
On the fleet I would have to hot wire one or two headlights a year so they could deliver that night when their switches smoked out. It was the Ford switches that went the most, followed close by the GM switches.

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On many American cars, the current supply for the lamps was very marginal. Going to a halogen doesn't pull a lot more current, but it still pulls too much more.
This is opposed to some British cars where the switches just burn up all the time anyway, even using the stock lamps.

Hmm, that's a cute idea. I like that. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Scott Dorsey wrote:

The CB built into all the Ford headlight switches even back in the '60s was rated at 22 amps, which was plenty of capacity to run all the exterior lights, when new; the main real culprit is age, affecting current draw and CB reliability. In the case of Ford, it was compounded by using marginal quality parts and very light gauge wire; there's a reason why it's always been called the "Ford flashing headlight syndrome", even though other makes have reportedly done it (just not as much).
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Just as a follow up, replacing the headlight switch so far seems to have cured the problem. Curious since the one that was in there wasn't that old.
Thanks again to all who replied.
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cheap china stuff.
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only problem is the headlights point straight up when using Chinese lights since they are calibrated on the wrong side of the planet.
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