alternator not charging but works ok?

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Deleted-user-3
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alternator not charging but works ok?

Post by Deleted-user-3 »

deisel astra, had exactly the same problem on one a few years ago...
alternators fine, stick a wire on the terminal and arc it on the engine and it sparks like a good un... run this to the +ve battery terminal and it seems to cure the problem..
question is, whats wrong with it? i thought dodgy wiring but exactly the same problem in two almost identical cars?
relay possibly? how do you check if a relay is knackered? not that i know which one it is anyway? :scratch:
All my advice should be taken with a rather large pinch of salt, all the gear, absolutely no idea whatsoever ;)
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Sparky James
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Post by Sparky James »

I would check the earth strap from the altinator to the enginseblock as the altinater is rubber mounted and the earth straps are a known weak point.
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Post by Deleted-user-3 »

cant be that mate, its not rubber mounted, me and my mate put the engine in...
that said though, do you think it could be an earth strap elsewhere else?
the fuel stop solendoid works ok so there must be an earth back to the battery from the block cos thats only got a switch live feed (i had to muller the imobiliser off the pump when i fitted a new engine so it just got the one wire to it)
will the direct link from thealternator to the battery cause any problems elsewhere?
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Sparky James
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Post by Sparky James »

Check the power lead then as they can go high resistance too the only other wire normally to the altinator is the charge light one and as long as the charge lamp comes on there no other thing to check with that.
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Post by Sparky James »

Oh if the main engine earth was suspect the starter motor would struggle :thumbright:

Edit fat fingers
Last edited by Sparky James on Thu Dec 31, 2009 8:46 pm, edited 1 time in total.
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Post by Deleted-user-3 »

the lead does run pretty close to the turbo....
i dont know what the other end connects to though? its all part of the loom..
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Post by ultimatehandyman »

Have you checked the voltage output from the alternator with a volt meter?

I used to have a combo van and the alternator was under charging, so I had to get a reconditioned one.

It was a real pain in the arse to change as well as the oil pump and servo are attached to the back of the alternator.


Or it could be the relay.

Do you have the owners manual for it, as it sometimes tells you in there which relayy it is. In the combo the realy was in the drivers footwell to the left behind a trim panel, or just below the steering wheel, can't remember where exactly :oops:

I remember that when I changed the alternator the relay was also goosed and required replacing, I just got a replacement from a car accessory shop for a few quid and swapped it over.
Last edited by ultimatehandyman on Thu Jan 14, 2010 10:30 pm, edited 1 time in total.
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Post by Deleted-user-3 »

not checked the output besides arcing it off against the engine, and connected direct to the battery it does charge it....
went to halfords to get a manual when i dropped the engine in and they dont do one! couldnt believe it! nearest thing i could find was a vectra manual...
prolly have to go buy a cheap multimeter... when i find the relay, would it be 12 volts across somewhere to switch another 12 volts? or 17 volts to switch 12 volts? could that be the reason? not enough output from the alternator (or a voltage loss in the cable) so it doesnt flick the relay so nothing gets through at all?
ill get a multimeter and have a prod about,cheers
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Post by uncle buck »

The thick red wire (could be a different colour) from the back of the alternator normally goes to the starter motor then carries on to the + of the battery terminal.
So this wire has 2 jobs to do....feed the starting current to the starter motor, then carry the charging current from the alternator to the battery. This wire often cause problems, especially on a diesel as they can suffer from poor starting if the glow plugs aren't up to scratch so they get a winding on the starter which will over heat the wire & over time cause a high resistance as Sparky James has mentioned.

I'm not aware of any relay being connected to this wire.

Replace the thick wire from the alternator straight to the battery terminal & this should cure your problem.


Cheers.
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Post by Deleted-user-3 »

great stuff... cheers uncle buck thats pretty much what i did, just attached it to the alternator and direct to the battery terminal...
used a length of 10mm earth cable...
so no probs to expect then, sound...
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Post by uncle buck »

Good stuff. :-)

If car manufactures weren't so tight they would run 2 wires direct...one to the starter & a separate one to the alternator...but I guess they save a couple of pence by combining the wire :roll:

I have seen this problem a few times...it quite often first shows up as the charging light on the dash glowing (not full brightness but just glowing) when the engine is running...then comes the flat battery etc....

Anyway glad you are sorted :thumbright:


Cheers.
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