Both headlamps blew at the same time ?

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65-440

65-440

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Ok, installed a headlamp relay harness last year and the lamps have been working great. Left the house before the sun came up yesterday morning, obviously had lights on ! soon as I took off from the light in noticed on the bumper of the car in front of me that my lights went out. turned the switch off then on again and still not lamps, immediately hit the high beams. High beams came on and within a few seconds they went out, now I got nothing but parking lamps. A quick glance at the volt gauge and its reading normal, no overcharge.
Checked the system out today and everything is working fine, minus the lights coming on. High beam indicator still lights up when switch is pressed. All grounds are good, fuses good. Power is getting to both bulbs on both low and high beams. I find it hard to believe both lamps blew at the same time just because. Anybody have any ideas or have had this happen before ?? Both high and low beam circuits have 30A fuses before the relays. Thanks, Erik
 
I'd be checking the lamp grounds. Have you actually pulled either lamp and checked continuity? There should be a low reading between any combination of the 3 contacts
 
Yes this happend to me 20 years ago.Both headlights blew at the same time.I replaced them and they blew again.Come to find out my voltage regulator was bad.Replaced it and never had another issue.
 
68383GTS said:
Yes this happend to me 20 years ago.Both headlights blew at the same time.I replaced them and they blew again.Come to find out my voltage regulator was bad.Replaced it and never had another issue.
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Ditto. Happened to me a few years back. Poor ground between the regulator and the firewall. The system was charging 16+ volts. tmm
 
Ok, started car with dvom on battery. 15.08V, checked resistance on ground circuit at both attaching bolts to regulator and was good.. 02 ohms on both bolt heads. Swapped regulators with a new one I bought as backup, same exact voltage. Might be on to something here. ....
 
You probably have voltage drop in the ignition harness. With key in "run" but with engine off, find your 12V switched ignition. Leave one probe on that connection, put the other probe on the battery positive post. If you read more than .3V (three tenths of one volt) you have drop in the harness. This drop ADDS to the VR setpoint.

15V is not enough to blow up headlights. It IS enough to boil a battery.
 
Thanks, I will do more checking. I was also wondering if I need different regulator due to the fact that i'm running a mopar electronic ignition. I bought a regulator for a 70 340 dart, which was dual point from the factory, think that is an issue?
 
No not an issue. Anything 70 / later is OK, what they want is to get away from the 69 / earlier mechanical style. But even those, if you buy a new replacement, are electronic internally!!!!
 
67Dart273 said:
You probably have voltage drop in the ignition harness. With key in "run" but with engine off, find your 12V switched ignition. Leave one probe on that connection, put the other probe on the battery positive post. If you read more than .3V (three tenths of one volt) you have drop in the harness. This drop ADDS to the VR setpoint.15V is not enough to blow up headlights. It IS enough to boil a battery.
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Ok, where would you recommend tapping in to the 12V ignition source. under the dash or under hood ? not sure if it matters or there is a preferred component, ie ignition switch to get the reading. obviously the easiest access would be easier !
 
You want as close to the regulator as you can get. You still have a ballast? One of the terminals comes from the key, and branches off to feed the regulator. Probe them with key on and your meter grounded to find the highest reading

Then leave your probe on that terminal, and transfer the ground probe to battery POS

Another way is to clip to the blue field wire for a 12V source.

You are trying to discover the "end to end" voltage drop. You most certainly DO NOT want to probe under the dash, as this may eliminate the actual problem and lead you astray

The circuit path for a factory car is.............

Battery.........starter relay.......fuse link.......through the bulkhead........to ammeter......through ammeter........out ammeter..........to ignition switch connector........through switch........out switch connector..........back out through bulkhead.......and branch off to field, VR, igniton

EACH of those is a potential problem. Your most likely is the bulkhead connector, the ignition switch connector, and the switch

More rare, bad ammeter connections or problems in the ammeter. More rare yet is the factory wedled splice in the black ammeter wire.
 
Thanks for the info, I will do some checking this evening. Will post my findings. Thanks again !
 
Ok, go back and double check. Put your meter on ground, and probe both or all 4 ballast terminals with key in "run" Makes sure you got the "highest" reading terminal. This is the one coming from the Ign switch.

Then check the bulkhead connector and the ignition switch connector for drop.

Check your 12V going INTO the ign switch. This must be done under load, that is with key "on"

This 1.6 V is being added to the "properly" regulating voltage of the VR, IE 14V + the 1.6 drop is 15.6 volts at the battery.
 
If lights were getting dim at idle, I suspect that the bulkhead connection is playing a role in this. You seem to be in good hands for checking the VR. LOL Could be incredibly tight manufacturing tolerances that got both lights to fail at the same time.
 
I lost the lights one time in a 65 Belvedere, turned out it was the dimmer switch.
Clean the contacts and everything worked again.
 
I had my wife keep an eye on the meter while I play with the wiring under the dash. I was reading the schematic and followed the under dash splice and saw a black wire going to the headlamp switch. soon as I grabbed the harness close to the switch the voltage dropped down to .25V, I let go and it went back up to 1.2V and stayed. I was able to get the voltage to fluctuate by messing with the headlamp switch connector. Nothing happened when playing with the bulkhead connector. Voltage was 12.5 going into the bulkhead and 12.5 coming out.
so after all this I decided to start the car and see what my output voltage was and it was at 13.7 at idle, and 14.01 at 2500rpm. Not sure what the hell I touched but the alternator output appears to be back to normal, but still have 1.2V drop on ignition harness ...... DAMN THIS !!
 
Here are the "big things"

Bulkhead connector

These are three for this problem.........

The red battery wire coming in, the black alternator wire going to the ammeter, and the IGN1 "run" wire

Ammeter itself and it's connections. These can be problem children right in the crimped / molded eyelets on the ends of the ammeter wires

The welded splice. Only way to check this is to pull the cluster and untape the black ammeter wire until you "get to" the splice.

If you have not done so, read the MAD article

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

Below, from that article is a simplified view of the main power

Power comes from the battery, to the start relay large stud, through the fusable link, and in through the BULKHEAD on the RED wire to the AMMETER. The power goes through the AMMETER, out on the BLACK ammeter wire to the WELDED SPLICE. Not shown, this branches off to the IGNITION SWITCH CONNECTOR, through the SWITCH, and back out the SWITCH CONNECTOR. From there, on the IGN1 "run" line, back out the BULKHEAD CONNECTOR

Also, of course, alternator charging current comes in through the black wire BULKHEAD CONNECTOR

ANY of these capitalized points can be causing this, or a combination of them

amp-ga18.jpg
 
The fact that you "got something" when you wiggled confirms you are on the right path.

Probe the battery feeding into the ignition switch connector. Do your "wiggle test" and see if that drops. Probe the ignition coming out of the connector in "run" Again, wiggle test. You should be able to "bracket" the problem by doing so.
 
Alright, traced the wire from battery to all under dash crap. Got battery voltage going into ignition switch (12g red wire) and 6.4v coming out (14g Brown wire) . Guessing ignition switch is bad, or wire connection
 
If this is with the switch in RUN, then that is about normal. The brown wire only has 12v on it when the ignition switch is in START. In RUN, then voltage you see on the brown wire is just being backfed on that wire from the junction of the ballast resistor and the coil +.

Keep testing.....
 
Yup. The brown wire should be "close to battery" when cranking
 
Ok, so voltage in and out of ignition switch are good. Ignition side of ballast matches the wire coming from ignition switch at 6.5v w/ key in run. The other side of ballast is only reading 10.6v, shouldn't that be close to battery voltage? Also found a semi burnt wire in my headlamp switch connector, the green wire that feeds the dimmer switch. I did check voltage drop with headlamp switch disconnected and it was still 1.4v.
 
That green wire is THE power feed to the headlights; it carries all of the headlight current from the the headlight switch to the dimmer, from which it gets routed to either the high or low beam filaments.
 
Yes I know that, and I will fix it. But still doesn't help my voltage drop/ over charge issue! At least I think it doesn't
 
65-440 said:
Ok, so voltage in and out of ignition switch are good. Ignition side of ballast matches the wire coming from ignition switch at 6.5v w/ key in run. The other side of ballast is only reading 10.6v, shouldn't that be close to battery voltage? Also found a semi burnt wire in my headlamp switch connector, the green wire that feeds the dimmer switch. I did check voltage drop with headlamp switch disconnected and it was still 1.4v.
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65-440 said:
The other side of ballast is only reading 10.6v, shouldn't that be close to battery voltage?
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If this is "switched" 12V or ign run, then yes.

Again, the path this takes is where you check. You need to traced back and forth. It's "easy" on paper, but not so easy in the car. For example, the ammeter connections are difficult, the welded splice nearly impossible

So check the easy stuff first and work towards the problem.

Example. Say you check the IGN 1 (run) coming out of the ignition switch and it's OK. This means the red battery wire coming through the bulkhead, the ammeter and connections, and the IG switch and connections are all good.

Most likely suspect is the IGN feed going back out through the bulkhead.

Example. Say you check the battery coming IN to the ignition switch is OK, and the IGN run going back out is low. This means the problem is "right there" either in the switch connector or the switch.

You have to wiggle stuff. Just touching your probe, say, to a bad bulkhead terminal might make it "better" (acceptable) or "worse" and show up the problem
 
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