Front Running lights driving me insane

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Nov 4, 2015
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Hello All - I was hoping your could help with what has become a version of torture. I have a '72 FJ40 that is in pretty good shape. I decided to update the lighting on the beast and replace the running lights, dash bulbs, turning signal indicators (in the cab) with LED - wich work perfectly escept for the front running lights. I alsorreplaced the fuse box with a new one that is OEM for the year fo my truck.

I spent an hour today replacing the fuse box which was a direct plug in play with the old one. What I mean is that I just copied the connections that were on the old box. After pushing everything back together, all the lights upgrades work except both the left and right side lights. Both back red running lights work when you turn them on - however the front yellow do not. One important note - both the front running lights worked prior to me doing this slight modification.

I looked for loose connections and other obvious culprits - however - found none. What I find interesting is that both rear running lighs work fine. Also, the front turn signal lights work fine.

Can anyone give me suggestion on where to find the potential problem?

It is diving me insane!
 

ginmtb

'74 FJ40 - my first!
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Hello All - I was hoping your could help with what has become a version of torture. I have a '72 FJ40 that is in pretty good shape. I decided to update the lighting on the beast and replace the running lights, dash bulbs, turning signal indicators (in the cab) with LED - wich work perfectly escept for the front running lights. I alsorreplaced the fuse box with a new one that is OEM for the year fo my truck.

I spent an hour today replacing the fuse box which was a direct plug in play with the old one. What I mean is that I just copied the connections that were on the old box. After pushing everything back together, all the lights upgrades work except both the left and right side lights. Both back red running lights work when you turn them on - however the front yellow do not. One important note - both the front running lights worked prior to me doing this slight modification.

I looked for loose connections and other obvious culprits - however - found none. What I find interesting is that both rear running lighs work fine. Also, the front turn signal lights work fine.

Can anyone give me suggestion on where to find the potential problem?

It is diving me insane!
Are your grounds good? Expose bare metal. That helped me with mine.
 
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I think the ground are fine. Nothing really changed related to the wiring - other than the fuse box switch out.

Question - if all the other LED's work fine - including the two rear running lights - why would I need a relay for the two front running lights?

Another question - are the 4 running lights independant from one another.

Admission - I am an idiot at electrical so please use small words that I might understand : )
 
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I am not familiar with led replacements, but i would try two things:

1. check for power at the bulb socket, if no power work back towards the fuse box. There should be some harness threads on here that might be very helpful with diagrams.
2. can you put in the old bulbs to see if they work?

this may help:
Free 72/73 FJ40 Color Wiring Diagram
 
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AlaskanWheeler - first - where in AK are you. I have been going to Southeast every year since 1974 to fish - love Sitka!

Now - to exemplify the level of my ineptitude - could you please be more specific regarding polarity - what should I be looking for? Since I did not mess with the wiring of the lights (except for the fuse box replacement) - I need more specificity.

Mark
 

AlaskanWheeler

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Sitka is beautiful to say the least. I live in Fairbanks and spend most of my time outdoors in and around the Yukon river...

Simply put, if the light is wired backwards it won't illuminate.
 
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Been up to Denali 10 times to date - Gods country.

I assume that would not happen at the fuse box since the connectors on the back of the box were untouched - all I did is unplug them and plug them back in at the same place on the new box. Therefore - I need to be looking elsewhere for this problem?
 

mtquivr

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Take one of the LEDs out and wire it directly to a battery. A 9 Volt battery will probably work.
 

78fj40mg

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Make sure all the contacts behind the fuse box and connectors are clean and well seated, and also make sure all the ground wires are connected.
 
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I second the polarity question--incandescent bulbs don't care about polarity, but LED's do. Of course, if your sockets are grounded right through the body, then they probably are okay. I think the only way your polarity could be reversed would be if your sockets were isolated from the body (rubber mounted), and there were 2 wires running to each light. Then the polarity could be reversed and with incandescent bulbs you'd never notice it.
 
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All - want to thank all of you for the guidance. In the end - it was a grounding issue. It amazes me how sensitive that particular element is.

I learned a great deal by absorbing all of your suggestions and methodically grinding through each of them. I now have a FJ that is totally lit up in all the right places. I would recommend to all the change out to LED - the difference is astounding.

Thank you all again!

Will be back with more clueless questions!
 

ginmtb

'74 FJ40 - my first!
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I learned early in the process as I fought parasitic leaks and other electrical issues that good grounds are HUGELY important! Glad to hear that's all yours was.
 
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