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1980 Steel Nose Headlight Issues Now!


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New headlight bulbs (H6024's) and now we have an issue.  Issues is with the old sealed beams also, so all 4 act as described below.

Driver light is good and bright.

Passenger light is dim.

Unplug driver headlight and the passenger light goes out!

Both headlamps test fine on drivers side.

Both are dim on passenger side.

 

Apparently lights worked ok until someone might have messed with wiring at the firewall.  Or maybe just age and from sitting?

Going to start troubleshooting tomorrow weather permitting.

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Thanks guys.  First thing I know is the passenger side light, housing and all has been changed so that is suspect!

Wondering about the light switch and dimmer.

I read that the light switch can be an issue on older Mack's.

What is odd is why the passenger light would go out if the driver bulb is disconnected/removed?

 

Edited by Wirlybird
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as stated above sounds like ground issue. the pass side goes out possibly due to it's back feeding ground through the driver side. disconnect driver side takes away a poor ground to pass side. corrosion in plug will do it. trace the harness; might have broken/ fried wire

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57 minutes ago, mechohaulic said:

if the housing was changed with an after market replacement, the headlight ground may have a pop-rivet to the assembly which isn't completing a good ground.

The passenger side was replaced and could be one of the aftermarket mounts but looks like a newer Mack replacement.

Will be checking grounds

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19 hours ago, Vladislav said:

What bus that bus bar came from??

Sorry I'm not a native bus specialist:)

The "buss bar" is just the terminal block on the inner fenderwell located near the radiator.

Edited by Wirlybird
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18 hours ago, Vladislav said:

What bus that bus bar came from??

Sorry I'm not a native bus specialist:)

Vlad, He left off an "s".. He means buss bar, as in big junction block..

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Brocky

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Thank you for improving my linguistic skills ones more, gentlemen!

In this particular case I figured it worth better investigation (for me to learn the lesson essentially) so made a bit of Google search. I figured from there that buss bar (bus bar also looks correct) and a junction block are not almost the same matter. Definitely both are a bar with a line of terminals. But buss bar is a solid metal bar with multiple connectors. So my understanding is it's for connecting multiple wires to the same potential providing minimal resistance between the terminals. This way it can't be used to connect contacts of different circuits and seldom used in automotive products (and that's why I never met the term). A junction block has every terminal electrically insulated from the others so its function is different.

Please correct me if I'm wrong since that's how I understood the subject but never used the term in practice before. My dad likes to joke that a person who tends to teach doesn't know the matter himself in many cases. And this time I'm just in a half of a step to be such the person:)

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Никогда не бывает слишком много грузовиков! leversole 11.2012

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Vlad

Your info is probably better than mine and I stand corrected!! I had heard the term used in a generic way but Buss bar must have more marine or aviation usage than automotive??

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Brocky

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9 hours ago, Vladislav said:

Thank you for improving my linguistic skills ones more, gentlemen!

In this particular case I figured it worth better investigation (for me to learn the lesson essentially) so made a bit of Google search. I figured from there that buss bar (bus bar also looks correct) and a junction block are not almost the same matter. Definitely both are a bar with a line of terminals. But buss bar is a solid metal bar with multiple connectors. So my understanding is it's for connecting multiple wires to the same potential providing minimal resistance between the terminals. This way it can't be used to connect contacts of different circuits and seldom used in automotive products (and that's why I never met the term). A junction block has every terminal electrically insulated from the others so its function is different.

Please correct me if I'm wrong since that's how I understood the subject but never used the term in practice before. My dad likes to joke that a person who tends to teach doesn't know the matter himself in many cases. And this time I'm just in a half of a step to be such the person:)

I think you are right.  Busbar or Bus Bar is how I find it and it seems that the specific use would be as a "power" supply or distribution point where one power line in and many possible lines out.

Terminal block or junction block would be a series of individual/independent "terminals".

I think on the Mack the terminal/junction block is used as a point where the fender wiring can easily be disconnected from the main harness.  In this case it enables you to undo the main harness connection to the headlight, blinker and parking light for the fender and then be able to remove the whole fender and its wiring as one unit.

I've always used the term Busbar in a generic way to mean a strip of terminals or connection points.

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Ok, now it seems that all is clear.

Sorry to stir the pot on a subject that had no direct relation to your original issues. But we better should use correct terminology to understand each other correctly.

BTW the part # for that 6-pole junction block is 71MR403P6 and it crosses to PAI MJB-4385.

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Никогда не бывает слишком много грузовиков! leversole 11.2012

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