Blowing a Fuse

[Challenger RTA]

Not confusing the issue you are having.:There have been issues with retro fitting headlight.with 9004 and 9007,The grounds locations on the socket are different. Keep this in mind.

 

[sdcbowler]

When not connected to the firewall connector and no headlights plugged in. You should get no reading between any color of wires at all. only should get a reading on same colors. With headlights plugged in you will be reading across the filament from one color to the other. All 3 blades or prongs on the same color wire are independent of each other. Ground Hi and low.

OK,
I understand what you have said. Now, lets forget about the harness, wires, and connectors on the harness. Lets focus on the single sealed beam, removed from the car, sitting on a bench, not connected to anything.

1. I lay it on the front surface and I see three prongs on the back .....looks like l _ l
2. I probe between the left and middle prongs, there is continuity
3. I probe between the two outer prongs, there is continuity
4. I probe between the middle and right prong, there is continuity

I didn't know if finding continuity between all the connectors indicated a good sealed beam, or a defective sealed beam.

Hope I am not confusing you. I'm having a difficult time putting this into words.

 

[sdcbowler]

Not confusing the issue you are having.:There have been issues with retro fitting headlight.with 9004 and 9007,The grounds locations on the socket are different. Keep this in mind.

Thanks for the sidebar. I don't think I will be doing that, but definitely good to know.

 

[pschlosser]

No matter which two of the three prongs I probed, there was continuity. This lead me to believe that all three are somehow connected within the sealed beam. I didn't know if that was normal or not.

That IS normal. Because the bulb filaments are technically a wire connecting the two terminals (on either side of the bulb)

In a lamp with both High and Low beams, one prong is common to both, and the other two each power one filament. However, I would NOT expect the two not-in-common terminals to show continuity at the bulb.

That said, stay focused and don't get off track. Test those side marker lamp assemblies (when unplugged from the harness, but still installed in the car) for continuity to ground.

Continuity can be tricky. In most cases, the bulbs will show continuity across their terminals, but ALSO show resistance in Ohms. It is, as many know, the resistance that causes the filaments to glow.

My definition of continuity is not simply "it completes a circuit," but rather, completes the circuit without much or any resistance. That is a short.

It can be tricky to tell the difference between the two, sometimes. On my digital meter (DMM) I have a setting that emits a tone when the circuit is completed. I often use this to test continuity. I've heard this tone simply by pinching a lead in each hand, wherein my body completes the circuit. There is considerable resistance reading on the meter, but it still makes a tone. Don't be tricked by this phenomenon.

 

[sdcbowler]

OK,

I will perform the tests and post the results later today. Thanks to both of you for all the good advice.

 

[sdcbowler]

Good Day,
Below are the tests that I performed. The results apply to both side markers.

Side Marker Test Parameters: Installed on vehicle, WITH bulb, NOT attached to harness

-Probed between the two leads

:Continuity indicated

-Probed between each lead separately and the case

:Continuity indicated

-Probed between each lead separately and chassis

:Continuity indicated



Side Marker Test Parameters: Installed on vehicle, WITHOUT bulb, NOT attached to harness

-Probed between the two leads

:No continuity

-Probed between each lead separately and the case

:Continuity indicated

-Plug = Has continuity with case .000…..No continuity with center contact in bulb housing

-Socket = No continuity with case……Has continuity with center contact in bulb housing

-Probed between each lead separately and the chassis

-Plug: Has Continuity

-Socket: No Continuity



Side Marker Test Parameters: Removed from vehicle, WITH bulb, NOT attached to harness

-Probed between the two leads

:Continuity indicated .004

-Probed between each lead separately and the case

:Continuity indicated

-Plug = .000

-Socket = .004



Side Marker Test Parameters: Removed from vehicle, WITHOUT bulb, NOT attached to harness

-Probed between the two leads

:No Continuity

-Probed between each lead separately and the case

:Continuity indicated

-Plug = Has continuity with case .000…..No continuity with center contact in bulb housing

-Socket = No continuity with case……Has continuity with center contact in bulb housing


Personally, I don't know what to make of these results.

 

[pschlosser]

I believe your side mark lamps check out okay.

The bulb in the side marker lamps connects via an outer shell and a center nipple. It is common for the outer shell of most automotive lamps to be grounded, and the inner nipple to have power AND (when no bulb installed) be isolated from ground.

Your tests seem to suggest this is testing correctly. The "Plug" goes to the lamp socket's outer shell, and also shows continuity with ground. The "Socket" goes to the lamp socket's center, and (when no bulb is installed) does NOT have continuity to ground.

I believe this is correct and normal and not your shorting problem.

I predict you can install the side marker lamps into the vehicle, and with NO BULBS installed, plug them in to the harness and power your lights without blowing a fuse.

All 3 blades or prongs on the same color wire are independent of each other. Ground Hi and low.

I'm sure @Challenger RTA has the best intentions, but aren't we talking about a Challenger with dual headlights? And dual headlights will have only two connectors at each lamp?

Focusing back on the side marker lamps, which seem to be testing okay: What if you went the other way, and plugged in ONLY the side marker lamps? No headlights, no turn signals, no parking lights. Can you power the lighting circuit, and see the side marker lamps working installed in the car, without blowing a fuse?

 

[sdcbowler]

After completing all the testing yesterday I also believed everything was in proper order. Thats why I had no conclusion afterwards....other than a big question mark floating over my head.....lol

I will do as you have suggested tomorrow.
-Connect side Markers with no bulbs. Depending on the results, I will then......
-Disconnect all lights except for Side Markers

Yes we are talking about a Challenger with dual headlights. The two outer sealed beams are for normal driving conditions and have three connectors on the back. The two inner sealed beams are the high-beams and only has two connectors on the back.

 

[Challenger RTA]

After completing all the testing yesterday I also believed everything was in proper order. Thats why I had no conclusion afterwards....other than a big question mark floating over my head.....lol

I will do as you have suggested tomorrow.
-Connect side Markers with no bulbs. Depending on the results, I will then......
-Disconnect all lights except for Side Markers

Yes we are talking about a Challenger with dual headlights. The two outer sealed beams are for normal driving conditions and have three connectors on the back. The two inner sealed beams are the high-beams and only has two connectors on the back.

Challengers have Quad headlights. Wiring is the same for dual headlights. Quad have added wires for the high beams two prong.hi low sockets have three wires. posted the dual beam for simplicity.

 

[sdcbowler]

Sorry....thats what I meant........ Two on each side.

 

[sdcbowler]

What I did today,

I used jumper wires from the battery (PWR/GND) to side marker and it worked fine.
I then connected one side marker to the harness WITH NO BULB, moved switch to first position and the fuse blew
I then disconnected dimmer switch and tried again with no bulb, and it again blew the fuse

Am I correct in thinking the control switches (head lights, dimmer, wipers) are grounded via the metal mounting bracket on the backside of the dash panel?

It seems there is no issue with the harness or any of the connections from the bulkhead disconnect forward. Is it possible the problem could be on the other side.......under the dash?

 

[pschlosser]

We know it has something to do with the lighting wiring harness in the engine compartment. Not within the interior, or dash wiring. At least not without more evidence. We conclude its in the forward engine area because simply adding a front side marker lamp to the circuit pops it.

 

[Challenger RTA]

If you suspect the switches.check them with the meter. Check each sw terminal to housing in all sw positions. There maybe more the one issue. The headlight circuit,power from battery and alt can be very distructive if there is a short. Is the instrument cluster in? When removing diconect battery. The back of amp meter will be hot if not disconnected. There is an instrument that will check the insulation of the wiring. A megger will show if there is a phantom short. 99% of people never heard of it. If you know someone that has one have them check it out. It might be better to get a new harness. Below is an example of damage of a over current from an other wire?

 

[sdcbowler]

If you suspect the switches.check them with the meter. Check each sw terminal to housing in all sw positions. There maybe more the one issue. The headlight circuit,power from battery and alt can be very distructive if there is a short. Is the instrument cluster in? When removing diconect battery. The back of amp meter will be hot if not disconnected. There is an instrument that will check the insulation of the wiring. A megger will show if there is a phantom short. 99% of people never heard of it. If you know someone that has one have them check it out. It might be better to get a new harness. Below is an example of damage of a over current from an other wire?

View attachment 104803

All of my harnesses are new and have never been used before. I can test the switches, but I don't know how. I only knew to check the terminals against the case to see if any were grounded out. would either one of you have the steps to test the switches and know what values, if any, I should or should not get?

Thanks

 

[Challenger RTA]

When checking from case to all terminals and you should get no reading that's a good thing
Check from power terminal to each load terminal you should get a reading.wiggle sw to see if you loose reading. a bad connection can blow a fuse. A new harness doesn't mean it's right. A processes of elimination will find it. The dimmer sw is for the cluster lights only.

Headlight sw in the top upper right of diagram

 

[sdcbowler]

I was able to test the light switch. With the switch in the closed position (on position), I probed between B1 and H.....the reading was .5 ohms.
I then probed between R and B2 and the reading was 4 ohms. None of the terminals had continuity with the case when the switch was in any position.

I don't know if the values mean the switch is good or bad.

 

[Challenger RTA]

As long as there is continuity in the two on positions from the power feed. your good.

 

[sdcbowler]

Guys,
I have an update. I removed the side markers from the vehicle, but left them connected, so they were just hanging in mid air. The results was when I switched the lights on, they came on and did not blow the fuse. Installed one of the markers on the vehicle, turned on the lights, and it immediately blew the fuse. You two probably already suspected, but it turns out that the case was grounding out against the fender. I remedied that, so the problem is solved.

Thanks to the both of you for all your knowlege, advice, recommendations, and assistance

 

[Challenger RTA]

Thanks for the update that will help other later on

 

[pschlosser]

Woohoo. well done.