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Weird Headlight issue?

Started by _Viper_ , Mar 16 2014 01:07 PM

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18 replies to this topic

#1 _Viper_

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Posted 16 March 2014 - 01:07 PM

Hey guys, ok some background first... Ive got a "painless wiring harness" fitted to my LH Sedan.

Everything works but I noticed my headlights are abit dull... I tried changing to new higher rated globes which barely helped... they are getting 12V and have good earths (both have seperate 12V feeds from the fuse box and both have their own separate earths to the body)

While i was playing around today I noticed they were the same brightness whether one headlight was plugged in or both but if I like half plugged one of the headlights in so it was barely touching the terminals and the bulb had a slight glow the headlight on the other side would brighten right up??? then if you plug it right in it dulls again... Ive attached a series of pics, hopefully you can make out the difference.

Now it would make sense to me if one was bright and connecting the 2nd made them both dull since their is more load possibly causing a voltage drop, but what is causing the 1st to go brighter with the 2nd "half" connected.

Edited by Viper, 16 March 2014 - 01:09 PM.

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#2 _Viper_

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Posted 16 March 2014 - 01:10 PM

A little hard to tell in the pics but the first pic the passenger side is dull, 2nd pic it brightens up quite noticeably in person then the 3rd pic it dulls out again.

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#3 _hutch_

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Posted 16 March 2014 - 01:51 PM

first thing to check is the you have the common terminal on the lights as earth,with the terminals up and the cross terminal at the top left hand terminal should be earth, high beam is opposite and the top one is low beam,if you have the hi beam terminal earthed and a live feed on the earth terminal you will get a feed back through the other head light filament to earth

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#4 _The Baron_

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Posted 16 March 2014 - 02:08 PM

Check your earth connections, electrickory will take any path back to earth, even if it has to pass through another element (high beam, low beam or both together) which will result in all sorts of light output levels.

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#5 S pack

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Posted 16 March 2014 - 06:34 PM

Voltage drop or poor earth issues.

Have you installed relays for powering the headlights or does the power come straight from the headlight switch to both headlamps?

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#6 Rockoz

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Posted 16 March 2014 - 06:39 PM

As above check that the earth is on the right terminal.

Whats the circuitry like for hi lo switching?

Using the original dipper switch?

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#7 _cliffos_

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Posted 17 March 2014 - 04:18 PM

I know LC LJ have internal circuit breaker in the light switch ,if LH has a similar set up ,I would try another switch or wire up a toggle switch to test it & if it works ,install 2 relays and just use your original light switch to switch the coil of the relays via your dipper switch.

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#8 hanra

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Posted 17 March 2014 - 04:56 PM

LH head light switch has an internal bi-metalic strip which is there as a fail safe in case of short circut in the headlight wiring as that circut is totally un-fused except for the fusible link if fitted. If there is a excessive current draw the bi-metalic strip will heat up and go open circut, cool down and close the circut, heat up, cool down, and so on....

The headlights will appear to blink on/off as this is happening so you know there is a fault in the headlight circut but wont leave you totally in the dark on a lonely country road! Saves the wiring loom from totally going up in smoke....

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#9 _Viper_

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Posted 19 March 2014 - 09:39 PM

Thanks Hutch, Rockoz and others

I had pinned the H4 plug incorrectly, the Low beam and earth were the wrong way around Doh! HEAPS brighter now... I wonder how high beam worked like that? :S before high beam just seemed brighter but not actually a higher beam.... Now its alot brighter and actually higher then the low beam...

Not using a relay, When I was fitting the painless kit I did email them and query it as they do not show a relay on their diagrams, they said if your using the normal 60/55w globes and a GM headlight switch you dont need one... But now its working correctly I am getting a 2V voltage drop (I was only getting about 0.3-0.4V drop before) And If I run a wire directly from 12V to the headlight it does get brighter again (obviously cos its getting full 12V) So I might look into fitting some relays in the near future. But even as it is now its very bright

so very happy..

Funny thing is the headlights passed a pit inspection as they were :S I literally could not drive at night unless there was street lighting or I put it on hi-beam (which was probably equivalent to my low beam now)

Thanks again guys. One step closer

Edited by Viper, 19 March 2014 - 09:43 PM.

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#10 _hutch_

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Posted 20 March 2014 - 06:27 AM

So your saying the original wiring had almost a full 12 volts across the lights and the painless has a 2 volt drop??? Or did read that wrong

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#11 Rockoz

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Posted 20 March 2014 - 10:07 AM

Relays on headlights are always a good idea. Not only to reduce voltage drop but to save burning out the dipper switch.

As you pretty much have all the gear, I would mount 2 relays per side.

One for each beam for each light.

Very easy job and reliability will be there along with brighter lights.

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#12 _hutch_

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Posted 20 March 2014 - 07:13 PM

a single relay for each beam is more that adequate but I like to fit a separate circuit breaker to each relay,some jap cars with a separate hi and lo/left and right fused lights require multiple relays just to get them to work Nissan in particular

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#13 _Viper_

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Posted 20 March 2014 - 10:35 PM

So your saying the original wiring had almost a full 12 volts across the lights and the painless has a 2 volt drop??? Or did read that wrong

Yea sorry, but original wiring I mean the way I had the H4's pinned the first time (wrong with the low beam and earth the wrong way around) when I was initially trying to work it out for myself I checked voltage and it was only .4 less then what I was reading at the battery. Now Ive got the pins the right way around and the headlights actually work well im getting a 2V drop

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#14 Rockoz

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Posted 20 March 2014 - 10:44 PM

No relays............................Adequate and work fine in most instances.

1 relay per beam................Lots better and reduces voltage drop to beams closest to relays.

Depending on wiring route and distance still voltage drop to other side

2 relays per beam..............Reduces voltage drop problems to very low levels to all beams.

Voltage drop increases heat in the wiring loom.

Increased heat creates more resistance.

More resistance creates more heat.

Get enough heat and your wires start leaking smoke.

Once all the smoke is gone out of your wires they arent any good any more.

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#15 Dr Terry

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Posted 26 March 2014 - 08:53 AM

No relays............................Adequate and work fine in most instances.

1 relay per beam................Lots better and reduces voltage drop to beams closest to relays.

Depending on wiring route and distance still voltage drop to other side

2 relays per beam..............Reduces voltage drop problems to very low levels to all beams.

Voltage drop increases heat in the wiring loom.

Increased heat creates more resistance.

More resistance creates more heat.

Depending on your wire size, 2 relays won't give any real improvement over 1 relay (for each beam). The big gain is not running thru thin wires to the dash switch & the dipper switch & out again. That's where the voltage drop happens.

A good 5 mm or 6mm wire from the alternator to the relay & then to each headlight is more than adequate.

Dr Terry

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#16 Rockoz

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Posted 26 March 2014 - 03:50 PM

Another reason behind the extra relays is a bit of redundancy.

Relays are known to fail.

When I did this set up I actually ran 6 relays because I had driving lights as well.

If 1 relay failed it didnt affect both sides.

It did happen a couple of times. But I was running 90/130 and 100W globes.

I ran proper 6mm2 wire from the battery to the relays, not the 6mm auto wire which I think is less than 4mm2.

Then 4mm2 wire to the globes.

A couple of 3 way relay bases mounted near the lights looked neat.

Dont ever use the boxy looking twin headlight relays. Used to be branded New Era but copies available in some places.

These relays fail quickly without much loading and will fail so that the lights turn on and off on their own.

Resulted in a flat battery in an inconvenient place.

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#17 Dr Terry

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Posted 26 March 2014 - 05:32 PM

Redundancy is a good reason, however I've been using the Bosch 30/40 amp type relays now for 45 years & as long as they have their pins pointed downwards, they NEVER fail. 2 x 100W globes draw 17 amps combined, well within the relay's capacity.

I reckon they are more reliable than GM-H's own headlight & dipper switches, which themselves have a very good reliability record.

Dr Terry