Seeking help with auto headlight electrical problem

[James Burleigh]

My son drives a 1985 Nissan 300ZX (photo). Now that he's on a nationwide band tour, I've been driving his car lately. I noticed that the high beam on the right headlamp (from perspective of driver) seemed to be burned out. So I bought a replacement lamp and installed it. Same problem.

Hmmm... Lights are f**ked up. Here's what's going on. BTW, the car had a short in the alarm system when we bought it, that caused the battery to die when ignition not on. That was "solved" by a professional by disabling the alarm system.

• Blue dashboard high-beam indicator light always on regardless of switch in high or low beam setting.
• On low-beam setting, left headlamp is low with good strength, right appears high-beam intensity, but not raised up or "high."
• On high-beam setting, left headlamp goes high-beam, right goes dim, or perhaps "low."

Summary: Left lamp seems to be working as it should for both low and high beams. Right lamp seems to be the one that's messed up.

The bulbs have three prongs (photo), with a female receptacle they plug into. As I understand it, the center prong is ground, and the left (driver's orientation) is high, right is low beam. Here are the readings I get on the female receptacle with the multimeter, holding the black lead on the center ground and alternately touching the left and right prong receptacles in high and low beam postiion:

When on Low Beam Switch Setting:

Right headlamp:

High prong: 12.2 V

Low prong: 0.02 V

Left headlamp:

H: -12.2

L: -11.01

When on High Beam Switch Setting:

Right headlamp:

High prong: 0.01

Low prong: 12.17

Left headlamp:

H: -0.6

L: -1.3

Not being a sparky, I guess I would expect to see the high-beam prongs show 12 V when the high-beam switch is on, and the low-beam prongs to be very low voltage. But the right headlamp seams to be working fine with the low and high beam, yet it's got real screwy readings.

Any insight into what's going on here? My best approach may be "do nothing." But alternately, if the right is working, can I tap into the wires leading to the female receptacle on that side and just splice them into the right-side receptacle? What's the meaning of the negative values for the right side?

Thanks in advance.

Jb

The Patient:

Headlamp (Oh! Is that my new digital StarCom captured by accident in the photo? :yahoo: )

Three Prongs:

 

[HYCLE]

Hi Hans, I took a look at the wiring diagram for this car. The center terminal is powered by the headlight switch and the lights are turned on by grounding the High or Low terminals. Now that you know this you can rethink the problem.

The fact that you have power to both headlights means you have a some sort of connection to the power fuse. Try testing the voltage at the headlight terminals with them connected. Connect your black lead of the voltmeter to battery ground and backprobe each headlight terminal with the red lead. Do this with one headlight disconnected while you test the other headlight. Then test again with both headlights connected and note any difference.

You should show 12 volts on the center terminal and less than .25 volts on the grounded terminal of the element that is switched on. This is opposite of what you would expect.So with the low beam lights on you should see 12volts at the center terminal and the highbeam terminal with the low beam terminal near zero since it is switched to ground.

I can send you the wiring diagrams but you might go blind and get more confused. The ground side of the headlights have the alarm relay, the passing light relay, etc. So if you have all good connections you could have a sticking relay causing the high beam to stay on for one headlight. You may have to locate each relay and disconnect it to see if your problems go away with that relay unplugged.

Take some new readings with the lights connected and let me know.

 

[Toecutter]

Every electrical problem is a bad ground.

You're welcome.

Hycle, way to re-quote the entire post right below it!!!

:clapping:

 

[James Burleigh]

Hycle, way to re-quote the entire post right below it!!!
:clapping:

Hey, Hycle's my friend. No fair busting his chops when he's helping out his buddy.

Only I get to do that: Hycle, what are you, a f**kin' RETARD?!



Jb

P.S. Thanks for the post, I will digest it, mess with the car in this lousy rain, and report back....

 

[Berde]

I used to have a 300ZX turbo, and my lights did the same thing at one point. Check the light switch conectors. You need to disassemble the turn signal pod from the steering wheel housing and clean and lightly sand the contacts (very fine sandpaper). Try bending them slightly (repeat slightly) so they make better contact with the terminals on the steering column. Through the years they sag and start loosing effectiveness. If that solves it, try find another pod (turn signal pod)since this trick won't last forever. If it does't it could be something else such as a relay or wire.

 

[Toecutter]

Hey, Hycle's my friend. No fair busting his chops when he's helping out his buddy.
Only I get to do that: Hycle, what are you, a f**kin' RETARD?!

From another of my cyber hangouts:

Subject: The "SNIP" Tool
The "SNIP" tool is a very powerful tool indeed, used by many an individual to comment on and reply to anothers information in a concise and carefully constructed manner. Properly used, the "SNIP" tool will assist in controlling the influx of carots ">" and provide a very readable summary of what is being discussed.

The proper "SNIP" is often contested and hotly debated, but it's use is not specifically nor categorically defined. In general terms, the SNIP tool should sufficiently shorten a replied-to message such that new information you provide is greater than that which is copied therein. For instance, if my reply to a message is "me too!" then the copied and included information should only contain one single line of text. Additionally, once a message reaches the "reply-to-a-reply-to-a-reply-to-a-reply" stage, the SNIP tool takes on even greater weight. Judicious administration of the SNIP is required of all individuals to ensure complete yet concise distribution of information.

Overuse of the SNIP tool is also dangerous, as some information is often required for your response to make any sense. For instance, if an individual asked a series of questions, and my reply is as thus:

"Yes.

Yes.

Black. Only once."

...then no one really has much idea what the original questions or topics were, likely even the original author. Including even a line or two of previous copied information is required for the outside reader to make heads or tails of these responses.

Please, exercise your right to SNIP...and do so with pride and honor.

The ever-addicting "ME TOO!" syndrome shall be discussed on a future soapbox.

 

[jekirby]

Sorry to get off topic, but "nationwide band tour" do tell/brag.

 

[HYCLE]

Hycle, way to re-quote the entire post right below it!!!

Hey, Hycle's my friend. No fair busting his chops when he's helping out his buddy.

Only I get to do that: Hycle, what are you, a f**kin' RETARD?!

Jb

Thank you gentlemen for your kind and helpful comments. Without your words of wisdom I am sure to forget to put down my kickstand and fall to the ground wimpering. I am sure when I locate my missing testicles I will be able to defend myself with a suitable outburst of even more idiotic unintelligible statements.

Thanks again for looking out for me and protecting me from the bad men that are out to get me.

Gratefully Your Friend

Mike

 

[James Burleigh]

Hycle, way to re-quote the entire post right below it!!!

Hey, Hycle's my friend. No fair busting his chops when he's helping out his buddy.

Only I get to do that: Hycle, what are you, a f**kin' RETARD?!

Jb

Thank you gentlemen for your kind and helpful comments. Without your words of wisdom I am sure to forget to put down my kickstand and fall to the ground wimpering. I am sure when I locate my missing testicles I will be able to defend myself with a suitable outburst of even more idiotic unintelligible statements.

Thanks again for looking out for me and protecting me from the bad men that are out to get me.

Gratefully Your Friend

Mike

Is he joking....? Or not? :glare:

Sorry, Mike! Didn't mean anything by it!

[SIZE=8pt]Retard.[/SIZE]

 

[HYCLE]

Is he joking....? Or not? :glare:
Sorry, Mike! Didn't mean anything by it!

[SIZE=8pt]Retard.[/SIZE]

Your humble apology is accepted. I will send you tickets to the Special Olympics as a sign of good faith.

OK, so if I can find where she hid my balls, I will be back in.

Check around her nightstand. She needs to keep them close for those occasions when you get to use them.

And Toe was right I found them in the nightstand drawer on the wifes side of the bed.

 

[Toecutter]

And Toe was right I found them in the nightstand drawer on the wifes side of the bed.

So, did you sack up and take them back, or leave them there, afraid of what she'd do if she discovered them missing?

 

[James Burleigh]

Sorry to get off topic, but "nationwide band tour" do tell/brag.

Hi, jekirby. Thank you for inviting a proud father to brag. My son is in a band called Go Kart Mozart. They are on a two-month tour of the U.S., hitting just about every state. Attached is a map of their tour route. They are currently in the Northeast, and play in Thomas, W. Virginia on March 2.

Jb

 

[Fred W]

Is he joking....? Or not? :glare:
Sorry, Mike! Didn't mean anything by it!

[SIZE=8pt]Retard.[/SIZE]

Your humble apology is accepted. I will send you tickets to the Special Olympics as a sign of good faith.

You don't need tickets when you're a competitor...

 

[odot]

I see that gokart mozart isn't hitting the dfw metroplex......should I be happy or sad?

 

[RadioHowie]

When does the calliope crash to the ground?

 

[Toecutter]

My son is in a band called Go Kart Mozart. They are on a two-month tour of the U.S., hitting just about every state.

Haven't heard of it. Are they headlining?

 

[Fred W]

When does the calliope crash to the ground?

After you get blinded by the light, of course...

Getting back on topic:

One thing I don't understand is how you could have measured -12V anywhere on a bike that has no negative power supply. Everything on a motorcycle is ~ +12V with the negative side being grounded.

Could it be that you reversed your test leads on that JB?

 

[James Burleigh]

When does the calliope crash to the ground?

After you get blinded by the light, of course...

Getting back on topic:

One thing I don't understand is how you could have measured -12V anywhere on a bike that has no negative power supply. Everything on a motorcycle is ~ +12V with the negative side being grounded.

Could it be that you reversed your test leads on that JB?

Very possibly. See Hycle post above.... Thanks.

 

[HYCLE]

[Getting back on topic: One thing I don't understand is how you could have measured -12V anywhere on a bike that has no negative power supply. Everything on a motorcycle is ~ +12V with the negative side being grounded.

Could it be that you reversed your test leads on that JB?

Hi Fred, the headlights he is testing are on a Nissan Car.

The terminal that is used for ground on the headlight bulb is connected to power and the filiments are grounded by the headlight switch. So if he had the negative lead of his volt meter connected to the center terminal and the positive lead connected to one of the other terminals he would read negative voltage.

It will be important for Hans to check the available voltage with the headlight connected as the load of the headlight will make bad connections more apparent. The idea is, you could have 12volts of electrical pressure but a bad connection chokes down the flow enough to not light a big light.

But hell you knew that, so I was just explaining it so Hans might get an idea what to check.