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Feb 21, 2007 11:38:32 GMT
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Aaaargh! I've got my re-test on Monday and this happens...
When I was doing the repairs to my Benz a few days ago, I noticed the battery charge light didn't come on with the ignition. This should have rang alarm bells but I was too pre-occupied with doing the work.
Consequently the battery was dead when I went to start it. I jump-started it and drove it home. This morning I went to investigate further, and yep, battery's dead.
I know that if the bulb is gone, it breaks the circuit and the battery doesn't charge (I found this out on a dark country lane one night...). But I've changed the bulb and it still doesn't come on. Could the Mig welding have fried the diode? I've heard of this happening before.
I'm pretty stumped. Electricals aren't my strong point at all. Can anyone shed any light on the matter?! (Pun intended...)
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Feb 21, 2007 11:45:47 GMT
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Have you tried whipping a multimeter onto the bulb end to see whether there's any current actually getting through? If so/not then keep trying at other points in the circuit to narrow down where it may be fried.
Were you welding close to the loom?
A friend of mine fried his rear loom doing welding on the bottom of his 1200 B110 sedan.
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Skyline: 1963 - 1973 - 1983 Sunny: 1982 450SLC: 1973 Navara: 1992 Gloria: 1992
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Feb 21, 2007 11:53:43 GMT
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I'll have to try to get hold of a multimeter and do that... or get hold of someone with one to come over and help! The welding was on the rear subframe and as far as I know, there's no wiring near there. My mate who was doing the welding reckoned there wasn't much danger to the diode as he wasn't doing much and it was in short bursts
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Feb 21, 2007 12:00:38 GMT
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If you put a jump pack or other battery in, does the charge light come on? It's not just that that particular battery is dead and needs a proper trickle charge? Whip another battery in and then get ahold of a multimeter and see whether the alternator is working, you should be getting about 15ish volts with it running and about 13.5 without.
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Skyline: 1963 - 1973 - 1983 Sunny: 1982 450SLC: 1973 Navara: 1992 Gloria: 1992
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Feb 21, 2007 12:24:45 GMT
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If you put a jump pack or other battery in, does the charge light come on? It's not just that that particular battery is dead and needs a proper trickle charge? Whip another battery in and then get ahold of a multimeter and see whether the alternator is working, you should be getting about 15ish volts with it running and about 13.5 without. Well, the battery is pretty new, and all the other dash lights come on. The battery's on charge at the moment so once that's finished I'll put it on and try it. Something that crossed my mind is that the dashboard illumination dimmer switch is removed (as it's broken), and I was thinking that the battery bulb light may be on the same circuit. But I bridged the terminals to get the dash lights to work and the charge light still didn't come on. Also, the front foglights are removed for MOT purposes... perhaps they are on the same circuit? I'll put them back in and see if that does any good. I'm clutching at straws here...
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Nathan
Club Retro Rides Member
Posts: 5,649
Club RR Member Number: 1
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Feb 21, 2007 12:33:13 GMT
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Did you disconnect the Alternator while the welding was going on, I have had the same thing before and realised it was because I did not disconnect the alternator.
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Feb 21, 2007 12:42:24 GMT
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Did you disconnect the Alternator while the welding was going on, I have had the same thing before and realised it was because I did not disconnect the alternator. No. I know I should have, as a precaution, but my mate seemed to think it'd be OK (he does welding every day so I just went with what he said really). I'm a bit worried I may have goosed the alternator.
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Feb 22, 2007 16:20:43 GMT
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OK I think I fixed it! I pulled the alternator to get at the voltage regulator at the back after skinning my knuckles on the downpipe trying to get it off "in situ". The voltage reg looked alright, the brushes were long enough to make contact with the commutator... all seemed OK. I noticed the contacts were all rusted up, so I cleaned them off with some 240 grit, hooked it up to the car again... hey presto, my charge light came on! I'll have to wait until I put the alternator back on properly before I can fire it up and (hopefully) watch the charge light go out again, but I reckon it's fixed. Best bit is, it was free. Thanks to Kyteler and BGTMidget for your input guys
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Feb 22, 2007 19:35:33 GMT
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For safety you should always disconnect either the battery or the alternator before doing any welding. Its normally a bad earth from the welder that causes the damage and when welding old cars you always end up getting a bad earth at some point due to rust,paint underseal or just general curse word.
Normally if a diode goes it ends up keeping the charge light on all the time.
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