When the dash got put back in last week the battery was still connected(we know), it shorted and popped the fuseable link. We replaced it, all seemed well.

Last night on the way home I lost my headlights. Still had running lights, turn signals, interior lights. Noticed the new Fusable link was loose in the ring connector, re-attached it, still no headlights. I switched to highbeams, Lights....

I drove home. All was well.

Had to drive it to work today, got stuck at work till after dark... Leaving the parking lot, hit the brakes and poof, no lights. Still have running lights, turn signals, this time, no interior lights....

Runs fine

Not funny anymore....

Ballast? Voltage Regulator?

The lights seem to get excessively bright before going out. (both last night and tonight.

Thoughts?

(The replacement underdash harness is being cleaned, tested, and repaired)

Steve

Check the bulbs, and the alternator output. Since the bulbs get bright just before they go out, the voltage regulator may be bad and allowing the alt to put out too much voltage and burn out the bulbs. Also I think the brake lites and interior lites are on the same fuse. Also check the dimmer switch, if the headlite bulbs check out OK.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The headlights are on a circuit breaker located in the main headlight switch. Either something is causing a current spike (bad voltage regulator?), or this circuit breaker is getting too touchy.

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Not likely the headlight switch/circuit breaker, since the high beams work.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The Headlight switch is new

I've heard bad regulator and lamps burned out as options. Any way to test these components?

Steve

If your voltage regulator and/or alternator are faulty, either because they are producing too high a charging voltage or because they are causing transient voltage spikes, it can burn out headlamps and other bulbs throughout the car. Check the headlamps with a simple continuity meter or ohmmeter. With the lens facing away from you, the three terminals on the back of the lamp are as follows:

Left vertical: Common ground
Top horizontal: Low beam feed
Right vertical: High beam feed

Put your meter across ground and low feed. If you see continuity (or anything other than infinite resistance) the low beam filament may be assumed good. Put your meter across ground and high feed. If you see continuity (or anything other than infinite resistance) then the high beam filament is good. If your headlights test out as good, then you may want to look at the beam selector kickswitch. It may be faulty, or its connector may simply be loose or corroded.

Brake lamps and interior/dash lamps are on a common fuse so that you'll know from inside the car that your brake lamps are dead. A common cause of this "Step on the brake/poof no lights" phenomenon is a failure of the wire insulation at the rear lamp units themselves, which sometimes touches the (grounded) socket and as soon as you hit the brakes, poof, short circuit and blown fuse. However, this can occur anywhere in the line, which starts at the brake lamp switch, runs up through the steering column, through the turn signal switch, back down the steering column and from there to the back of the car.

It sounds like you've got multiple issues at work.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

i have had 2 older vehicles which had the same problem, no headlamps but the high beams worked. in both cases the high beam/dimmer switch on the floorboard was the problem.
hope this helps.

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mo-par to ya!

Ok,

Alternator tested OK,

Voltage regulator did not test ok,
replaced the voltage regulator.

Tested the bulbs.

Headlights - Popped
Interior lights - Popped
Dash bulbs - Popped

Replacing worked for everything but the dash bulbs.

Thanx for the help folks!
Steve