Passenger low beam won't work

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kdiqq
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Passenger low beam won't work

Post by kdiqq »

For some reason I feel like I've asked this before. I apologize if this is a repost. I can't get my passenger low beam to work. Both high beam works great and I have changed both bulbs but I'm not getting power to the bulb. Is there a headlight relay somewhere?! I looked behind the dash and couldn't find what appeared to be a headlight relay, but I did find a strange box underneath the passenger seat...

Any tips?!

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1977 Austrian 710M
undysworld
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Re: Passenger low beam won't work

Post by undysworld »

Breaker tripped or fuse blown? According to the schiz, they are separate.
kdiqq
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Re: Passenger low beam won't work

Post by kdiqq »

Nope, fuse looks like it's good....
1977 Austrian 710M
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Hotzenplotz
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Re: Passenger low beam won't work

Post by Hotzenplotz »

my cristal ball is out of order today, but I can give you a few general remarks.

there is one relay switching BOTH sides from high to low beam. If the relay is faulty you can't get high beam.

the driver side front lights come straight from the dash wiring, the passenger side come via a multi connector behind the dash.

take a tester and follow the cable, until you find voltage...
Cheers
Albert
========================
My Pinz has NEVER been with any army
kdiqq
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Re: Passenger low beam won't work

Post by kdiqq »

So is there a controlling relay for the low beams??

Let me know when that crystal ball gets working. Have you checked it's relay? :)

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Hotzenplotz
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Re: Passenger low beam won't work

Post by Hotzenplotz »

kdiqq

there IS ONE relay in the path of electrons flowing to both the low and high beam bulbs :-)
Image
it sits next to the indicator relay and defaults to low beam, and if you pull the indicator lever towards you, it switches to high beam.
this switching is done for BOTH sides, so you can rule out the relay.

do you have a wiring scheme for your truck ? depending on country , year, model, position of the moon and other irrelevant contributing factors there are minor to major differences in colorcoding, relays, fuses, ....
Cheers
Albert
========================
My Pinz has NEVER been with any army
kdiqq
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Re: Passenger low beam won't work

Post by kdiqq »

Ah! Very valuable information! Thank you!!!

I do and I've looked through it a few times. I am having trouble remembering what I found.

Mine is Austrian so I think what's in my service and owners guide is correct.

At the end of the day, I'm just going to need to manually trace everything :(

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1977 Austrian 710M
Texas710
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Re: Passenger low beam won't work

Post by Texas710 »

Check your grounding points. I have found most my issues with electrics were faulty or non existent grounds.
kdiqq
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Re: Passenger low beam won't work

Post by kdiqq »

Is the ground for the low beam and high beam different?!

If it is then that could totally be it....

I am hoping to figure it out this week. I have the Pinz down for the week to knock several things out, including changing all fluids, fixing a tranny leak, and adding an oil temp gauge. If I can get all this done I will only have the wiper motor to worry about!
1977 Austrian 710M
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Jimm391730
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Re: Passenger low beam won't work

Post by Jimm391730 »

The bulbs themselves share a common grounding point between the high and low beams. Get yourself a very sharp pin probe and you can prick though the wire insulation, looking for voltage, as you move from the bulb back towards the high/low beam relay. Unlike most vehicles, the stock Pinz high beam relay "latches" either high or low, but it has only one output for either - so it is most likely between the relay and the headlight. The first thing I would check is to unplug and re-plug any and all wiring harness plugs that you can find under the dash; I would think that a connector or the wire crimps in the connector are likely to be the culprit.
Jim M.
712W and 710M
kdiqq
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Re: Passenger low beam won't work

Post by kdiqq »

Never trust these fuses! I finally got it multimeter on it... the fuse had corroded on one side and was not making contact... swapped with a new fuse and it's good as new.

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undysworld
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Re: Passenger low beam won't work

Post by undysworld »

A multimeter is your friend. :wink:
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