headlights are not working . ground issue ? 1973 dart slant 6

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moparjon

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1973 dodge dart slant 6 . I just got this car a few days ago . The previous owner said he bypassed the alternator gauge by connecting the two wires that go to it together . He said it was because the gauge was causing a NO POWER condition as in none at all . is that possible ? . The Headlights are not working . i think it is a ground issue , but i am not sure .

With the HL knob pulled out to the first and second step , just one front parking light comes on steady , and both back lights and rear side marker lights come on . All other outside lights work normally with first step of switch except for the two front side markers . Same for second step , except with the right turn signal turned on , it stops blinking . The headlights do not come on . It is not the footswitch . The footswitch pigtail is showing power at all three terminals . Without footswitch attached . Both headlight pigtails are showing power to all three terminals . All are showing almost full battery power 12.27 + or - . That is not right . One "should" have no power for ground , correct ?

None of the dash lights light up either as far as i can tell .

The negative battery cable and connections and ground there all test good . I am suspecting where the other two wires come together where that attaches near the radiator , but , I didn't want to start cutting into them without ruling out other things .

Can it be the Headlight Switch ? ( i am looking for the extra one i have right now )
Would the cluster ground , or lack of , cause this full power symptom ?
Where are the grounds on a 1973 dart slant 6 , besides the one going from the firewall to the engine top ? and the rad area .
What else am i forgetting to check ? anything the previous owner might have unknowingly done while messing with the alt gauge ?

Thank you for your time and thoughts .
 
Well you need to do some actual TESTING, not guessing.

FIRST if you do not have such, wander over to MyMopar.com and download both volumes of the 73 service manual, and while there, go to the wiring section at MyMopar and download the simplified aftermarket diagrams, which can be easier to follow

SOME OF those manuals got there because of some of the guys right here!!

Ammeters and the ammeter circuit can be a big problem. Read this article to find out the why


PART OF the reason your tail/ park/ etc lamps are working is that the headlight switch has TWO SEPARATE power sources

The power for tail/ park/ instrument lamps comes from a fuse in the panel.

But the HEADLIGHTS ONLY power comes direct from a splice in the black ammeter wire a few inches from the ammeter. That wire goes to a different terminal on the light switch, which has a circuit breaker built onto/ into the light switch.

When you pull the HL knob all the way out, the HL power goes down to the DIMMER SWITCH (as mentioned above. It is a simple 3 terminal, double throw switch. This means that with the HL switch "on" there are always two terminals of the dimmer that should be "hot"

If you have power to one terminal of the dimmer and no others, and operating the switch does not change things, then the dimmer switch is bad. If you have power at two terminals and no lights, the trouble is out in the engine bay

If you have no power at all at the dimmer, you have problems up under the dash, time to pull the light switch, and probably, the cluster

ENGINE BAY: After headlight power leaves the dimmer switch, high and low beam power goes out on separate wires through the bulkhead connector, around the fender to the headlights. Often, the headlights are BOTH grounded through ONLY ONE screw. Start by running along that harness and checking for ground screw(s) and making sure they are so

It is not unheard of that headlights can BOTH burn out!!!

If you had power at the dimmer, go out into the bay, and using your manual/ diagram, probe the bulkhead connector for the head lamp hi and low beam and see if you have power there. If so, move on to the headlights themselves
 
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67Dart273 said:
If you have power to one terminal of the dimmer and no others, and operating the switch does not change things, then the dimmer switch is bad. If you have power at two terminals and no lights, the trouble is out in the engine bay
67Dart273 said:
ENGINE BAY: After headlight power leaves the dimmer switch, high and low beam power goes out on separate wires through the bulkhead connector, around the fender to the headlights. Often, the headlights are BOTH grounded through ONLY ONE screw. Start by running along that harness and checking for ground screw(s) and making sure they are so
Click to expand...
Click to expand...




Thank You . There is power to all three terminals at the dimmer switch . There is power at the inside and outside of the bulkhead on the high and low beam wires . It is close to full battery voltage 11 - 12+ volts . There is power at all three headlight terminals . Both sides . With and without headlights attached . Again , 11 - 12+ volts for each terminal ( all 6 ) . I tried a known good headlight and it didn't work .

I checked the ground screw you mentioned , but i am not sure i am doing that right . I tried the multimeter with one probe to the positive battery post and the other probe on the ground screw connection near the radiator . It shows 12+ volts . I didn't see any other grounds along the fender . Not sure what to do next .
 
At this point you are either down to a ground issue or the headlights are bad. To check that, pull out either lamp a little so you can access the connector, with the headlamp still connected. With the HL switch on, clip your meter ground to the battery neg. to start with and probe the connector. 1 of 2 will have power at a time and the other is ground, so this can be confusing.

With HL power OFF you can first identify the ground terminal by probing the connector for continuity

Here is a headlight connector, BK is ground here

HL.jpg

Anyhow, one of the two "non black" should have power depending on whether the dimmer is in hi or low. So with the lamp connected, and lights powered on, if you show power on say, lo beams, and the ground is good, it is gonna be the lamp.

You can use your meter and "ohm" the lamp. All three pins show continuity to each other on a good lamp
 
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