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Post by Tealcres on Jul 26, 2004 11:09:06 GMT 11
Not long after purchasing the 2000 Mu we noticed the lights were not working. We replaced the bulbs and they blew the fuse within 2 weeks. Had the alternator and battery replaced as charge was inconsistent.
however, the Headlights fuses (both) just went again - anyone have any idea as to what may be causing this?
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Post by James W on Jul 26, 2004 11:35:32 GMT 11
The alternator and battery should have no effect on your problem. If the alternator went way over volts it would more likely blow the bulbs rather than the fuse, that and along with boiling the battery and blowing other electrical equipment. Low volts would not have an effect, other than dimm lights and stuff not working.
I hope no one sold you the alternator and battery idea as a fix to the fuse problem.
It may be that the wiring truly does have a fault, and worst of all it is intermitiant.
What wattage are the new bulbs? Is the fuse approtiate to the wattage? Has the fuse been replace at sometime in the past with one of to low a ratting? What is fitted?
Are the bulb holders clean with no crud/rust that could cause a short? Inspect for chaffing and shorts in the wiring wherever you can get access.
It may be the irregular charging you were experencing is due to the short comming and going placing large loads on the system but not quite enough to always blow the fuse. This intermitant fault will cause the apperance of irregular charging and iregular alternator/battery voltage.
If a autoelectrican is doing this would I would suggest he/she fix the problem rather than part swap the problem at your expense. In otherwords diagnose the problem not guess it.
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Post by Tealcres on Jul 26, 2004 12:49:55 GMT 11
Thanks James
Yes, the auto electrician, suggested we needed to replace the battery and alternator as the alternator was overcharging - apparently they got evidence of this when running tests.
Now the fuse has blown on both lights (seperate fuses) and they are lost for what do do next - have given us higher amped fuses to see if this remedies the problem - will keep you updated - will check for any obvious signs of damage.
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Post by James W on Jul 26, 2004 15:33:38 GMT 11
It must be two seperate problems then, alternator and lights
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Post by geeves on Jul 26, 2004 17:59:12 GMT 11
If both blow at the same time I would be looking closly at the bulbs and fuses as after the fuse each is a separate circuit. I belive the bulbs should be 60/55 wats and the headlight fuse is a fusable link Im not sure of the ampage but its probably 20 - 30 amps which is more than double tha bulbs requirement. I have heard of people useing 120 watt bulbs with no problem although not recomended.
Does the fuse blow imediatly you turn the lights on, or after some time Is it when driving on bumpy roads of going round left or right corners All these things can be symtoms of the cause.
I saw a Nissan mistral at the auto sparky who did my alternator with what started as a similar problem. He had after market corner lamps which had been installed by a previous owner He took it into the bush Knocked one off which shorted out but it didnt have a fuse Now the owner insurance Co and Warrentee company are discussing who should pay for a new wiring loom.
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PeterSchurms
Isuzu Junior
Black 95' 3.1 MU Auto in Melbourne
Posts: 132
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Post by PeterSchurms on Jul 27, 2004 12:15:26 GMT 11
I had a similar problem. A real barstard to diagnose and I tried many things. It turned out to be a wiring issue. The problem appeared to be random….. I found out that driving above 80kms/hr or slower into a strong head wind in heavy rain would cause the light to blow. If you installed a new fuse everything would be fine. There was a exposed wire that would only short out if there was water and a strong wind to blow it back onto a metal earth.
If its power related / high current related, the following Yr 10 science may help may help. I am a little rusty on old school stuff, I think its right.
Power = Voltage * Current so...
Current = Power / Voltage
If lights = 65W each
65w/12 = 5.4 Amp per light
If lights = 120W each
120w/12v = 10Amp per light
Also, make sure you have a working fire extinguisher in your truck, if the fuse is too big you might start a small electrical fire… and there’s another story.
Hope this helps
Pete
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Post by Tealcres on Jul 27, 2004 14:34:39 GMT 11
This is good feedback thanks - i will do a good checkover of the wiring.
to answer question below - the fuse blows when i turn the lights on - not when running - and not every time!
Bulbs were blown the first time, once replaced with new bulbs it has been the fuses that have blown (both of them) and this has happened twice - both times when turning the lights on there just are no headlights
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Post by James W on Jul 27, 2004 16:01:42 GMT 11
Tealcres - Your math is spot on, but the calculations are for normal operation. Select a fuse about 120% of that calculated. Others may say differantly, but the point is a little more than 100% to avoid blowing. That and a cold bulb/filiment is lower resistance so a 65W bulb will draw more than 65W very briefly as it turns on.
- Cheers.
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