Right head-light too dim

amu1983 · 4th February 2007, 01:33

My right head light has been glowing too dim since past few days. I know, this happens due to weak battery, but don't think, that's the issue. The start-up, power windows work fine, just as they used to, and the battery is new.

The bulbs were also recently changed. Could there be any fault with the wiring? Has anyone experienced this ?

low_bass_makker · 4th February 2007, 03:36

check out the fuse.......

theMAG · 4th February 2007, 10:59

One headlight wont dim due to a low battery. The wiring is shot.

nitrous · 4th February 2007, 11:40

Its the relay aka cutout!

tsk1979 · 4th February 2007, 12:24

Or just the terminals in the holder are dirty.
Did you take out the bulb from assembly and light it up to see if its bright?
If it is that means your reflector, HL assembly glass is too dirty

danlalan · 4th February 2007, 13:05

i face the same problem...one headlight is a bit dimmer than the other one...have no cutout/relay...but what we colud do is change both the holders..
Will be going in the evening past sunset to do that...

amu1983 · 5th February 2007, 22:21

>> One headlight wont dim due to a low battery.

That's not true. A car's electrical system is smart to divert more power to one of the headlights in case of a weak battery. I've observed this with my old fiat too. It's usually the left headlight that receives more power, for some reason.

Anyways, will take the car to a mechanic and sort it out soon.

gd1418 · 6th February 2007, 12:11

Have heard this explanation for the first time. Can anyone throw some more light on this phenomenon?

Quote:

Originally Posted by amu1983

>> One headlight wont dim due to a low battery.

That's not true. A car's electrical system is smart to divert more power to one of the headlights in case of a weak battery. I've observed this with my old fiat too. It's usually the left headlight that receives more power, for some reason.

Anyways, will take the car to a mechanic and sort it out soon.

Jaggu · 6th February 2007, 12:27

its wrong.

well just check the wiring and connectors, especially the grounding for your "dim" headlights, also are u running stock 55/60 or upgraded?

tsk1979 · 6th February 2007, 12:53

Quote:

Originally Posted by amu1983

>> One headlight wont dim due to a low battery.

That's not true. A car's electrical system is smart to divert more power to one of the headlights in case of a weak battery. I've observed this with my old fiat too. It's usually the left headlight that receives more power, for some reason.

Anyways, will take the car to a mechanic and sort it out soon.

Smart? What smart.
All the electrical system does is connect the headlamps to battery via a relay.
No advanced ECU or something where.
When battery goes both headlamps will go dim.

esteem_lover · 6th February 2007, 12:57

The relay could be designed to cut down the power to the right bulb to avoid glare to the oncoming vehicles.

tsk1979 · 6th February 2007, 14:01

Quote:

Originally Posted by esteem_lover

The relay could be designed to cut down the power to the right bulb to avoid glare to the oncoming vehicles.

Havent seen anything like that in any of the cars whose electricals I know somewhat.The only way to cut power would be to add a resistor in the right headlight circuit so that you get lower voltage on the bulbs.
So you are running a 12V bulb on maybe 10 volts, which nobody would like to do.
So the only thing could be using a lower wattage bulb on the right side headlight, which is not the case in any of the cars.
Most cars in India come with 60/55W 12V Halogens now in case of H4

amu1983 · 7th February 2007, 21:09

Update - The battery is weak, and is due for change.

My bulbs are standard 60/55W.

To those who don't believe the 'magical' phenomenon, the explanation is very simple. Each bulb has two filaments - high beam and low beam. Normally, only one of them glows and entire 12V is applied on one of the filaments. When the battery goes down, a simple electromechanical switch causes the two filaments to get connected in series (one after another), and 12 V is applied onto both. Thus, each gets only 6 volts. Hence the dimming. The left bulb is given a higher 'priority' and is dimmed in such a manner only if the battery is really down. The right bulb is first victim.

Even the old fiat does this.

tsk1979 · 7th February 2007, 22:33

So how is this preference given? If you simple connect two bulbs of equal resistance in series both will get the same voltage.
Basic physics.
I would really be interested in knowing how a simple electromechanical switch "gives preference".

shyamhegde · 7th February 2007, 23:21

But so far I believed that if the car battery is weak and can not hold sufficient charge, major problem is to start the engine. Once the engine is running, the alternator produces enough voltage/current to drive the electrical. (though I read on ICE section that Sam had encountered a sound quality issue in his car because of weak battery). So headlight also should get sufficient voltage/current to run at optimum ( a 60/55 factory spec). Also I don’t see any benefits of running both the filaments of the bulb in series. At least on my Santro it has no such 'feature'.

4th February 2007, 01:33	#1
amu1983 BHPian Join Date: Feb 2007 Location: Pune Posts: 144 Thanked: 0 Times	Right head-light too dim My right head light has been glowing too dim since past few days. I know, this happens due to weak battery, but don't think, that's the issue. The start-up, power windows work fine, just as they used to, and the battery is new. The bulbs were also recently changed. Could there be any fault with the wiring? Has anyone experienced this ?
	() Thanks

4th February 2007, 03:36	#2
low_bass_makker Senior - BHPian Join Date: Mar 2006 Location: Faridabad Posts: 6,815 Thanked: 305 Times View My Garage	check out the fuse.......
	() Thanks

4th February 2007, 10:59	#3
theMAG Distinguished - BHPian Join Date: May 2006 Location: Avon, CT Posts: 7,217 Thanked: 1,807 Times View My Garage	One headlight wont dim due to a low battery. The wiring is shot.
	() Thanks

4th February 2007, 11:40	#4
nitrous Senior - BHPian Join Date: May 2004 Location: UAE/Lon/Madras Posts: 6,965 Thanked: 325 Times View My Garage	Its the relay aka cutout!
	() Thanks

4th February 2007, 12:24	#5
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,825 Times View My Garage	Or just the terminals in the holder are dirty. Did you take out the bulb from assembly and light it up to see if its bright? If it is that means your reflector, HL assembly glass is too dirty
	() Thanks

4th February 2007, 13:05	#6
danlalan Senior - BHPian Join Date: Nov 2005 Location: mumbai,JUHU Posts: 1,636 Thanked: 263 Times View My Garage	i face the same problem...one headlight is a bit dimmer than the other one...have no cutout/relay...but what we colud do is change both the holders.. Will be going in the evening past sunset to do that...
	() Thanks

5th February 2007, 22:21	#7
amu1983 BHPian Join Date: Feb 2007 Location: Pune Posts: 144 Thanked: 0 Times	>> One headlight wont dim due to a low battery. That's not true. A car's electrical system is smart to divert more power to one of the headlights in case of a weak battery. I've observed this with my old fiat too. It's usually the left headlight that receives more power, for some reason. Anyways, will take the car to a mechanic and sort it out soon.
	() Thanks

6th February 2007, 12:27	#9
Jaggu Team-BHP Support Join Date: May 2004 Location: Bangalore Posts: 20,215 Thanked: 15,907 Times	its wrong. well just check the wiring and connectors, especially the grounding for your "dim" headlights, also are u running stock 55/60 or upgraded?
	() Thanks

6th February 2007, 12:57	#11
esteem_lover Senior - BHPian Join Date: Jul 2006 Location: Madras/Py Posts: 7,556 Thanked: 502 Times View My Garage	The relay could be designed to cut down the power to the right bulb to avoid glare to the oncoming vehicles.
	() Thanks

7th February 2007, 21:09	#13
amu1983 BHPian Join Date: Feb 2007 Location: Pune Posts: 144 Thanked: 0 Times	Update - The battery is weak, and is due for change. My bulbs are standard 60/55W. To those who don't believe the 'magical' phenomenon, the explanation is very simple. Each bulb has two filaments - high beam and low beam. Normally, only one of them glows and entire 12V is applied on one of the filaments. When the battery goes down, a simple electromechanical switch causes the two filaments to get connected in series (one after another), and 12 V is applied onto both. Thus, each gets only 6 volts. Hence the dimming. The left bulb is given a higher 'priority' and is dimmed in such a manner only if the battery is really down. The right bulb is first victim. Even the old fiat does this.
	() Thanks

7th February 2007, 22:33	#14
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,825 Times View My Garage	So how is this preference given? If you simple connect two bulbs of equal resistance in series both will get the same voltage. Basic physics. I would really be interested in knowing how a simple electromechanical switch "gives preference".
	() Thanks

7th February 2007, 23:21	#15
shyamhegde BHPian Join Date: Dec 2006 Location: Bangalore Posts: 284 Thanked: 5 Times View My Garage	But so far I believed that if the car battery is weak and can not hold sufficient charge, major problem is to start the engine. Once the engine is running, the alternator produces enough voltage/current to drive the electrical. (though I read on ICE section that Sam had encountered a sound quality issue in his car because of weak battery). So headlight also should get sufficient voltage/current to run at optimum ( a 60/55 factory spec). Also I don’t see any benefits of running both the filaments of the bulb in series. At least on my Santro it has no such 'feature'.
	() Thanks