should the alternator be earthed?

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should the alternator be earthed?

Postby l1ttle_d3vil » Fri May 27, 2005 8:41 am

ive got my alternator all wired up, but when the cars going my battery is only reading 12.25v and im told it should be about 14.1v if the alternator is charging. the warning light on the dash goes out once the car starts. there is a bolt/screw on top of the alternator, i don't think theres any voltage on it (gives a weird signal when i put a multimeter on it). is this meant to be an earth? or should those three wires be the only things i need (batt, ign, warning light)? im guessing it should be earthed but just want to make sure first :roll:

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Postby ee904age » Fri May 27, 2005 8:46 am

That nut on the top is for the main charge wire I think. And im no sparky by wouldnt the alt earth itself through being bolted to the engine...
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Postby 3T-Rona » Fri May 27, 2005 6:48 pm

yeh it's earthed thru the bracket off the block, sum have additional earths which arent gonna harm it, if it reads 12.25v then its charging (as it would drop below 12 with coils and acc drawing from the battery unless it was a new fully charged battery if it wasnt charging) it sounds more like ur regulator is shagged because its not allowing the charge rate to rise to 14.25v's. if the 'weird bolt' on top is seperated from the alternator by a nylon washer or plastic washer then it is not an earth and should not be earthed, if it directly touches the housing then it will not matter if u earth it or not.
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Postby ee904age » Fri May 27, 2005 7:25 pm

That bolt should have a big white wire coming off it, through the fuse box and back to the battery (+ve terminal)
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Postby solberg Fan » Fri May 27, 2005 9:00 pm

Make sure you give a few revs when testing for charge. some alternators need a bit before they become effective.(sp?)2000rpm will be sweet.
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Re: should the alternator be earthed?

Postby Malcolm » Fri May 27, 2005 9:47 pm

l1ttle_d3vil wrote:there is a bolt/screw on top of the alternator, i don't think theres any voltage on it (gives a weird signal when i put a multimeter on it). is this meant to be an earth? or should those three wires be the only things i need (batt, ign, warning light)? im guessing it should be earthed but just want to make sure first :roll:

cheers

are those 3 wires all reasonably small ones in a 3 pin plug? if so, then that bolt/screw that you're talking about is the output of the alternator, and should, as already mentioned, run into your fusebox to a big fuse (around 100A). Without that connected you will get no charging from the alt.
And unless the alternator bracket is made of plastic, it will be earthed very well so don't worry about that
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Postby ChaosAD » Fri May 27, 2005 10:47 pm

Could still be worthwile running a few decent earths through the engine bay. From the battery to the alternator and starter at least
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Postby 3T-Rona » Sat May 28, 2005 9:48 am

yeh im sure u could buy one of those riced up earthing kits off trademe, my output wire comes off the bak of the alternator, as do most, but im not 100% sure its a 4age one, maybe the gze alternators are different, who nows.
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Postby NA Drifter » Sun May 29, 2005 8:10 pm

don't earth the wrong part... as they will be very nasty!! Mate did it to his car and end up blowing lots of fuse!
Is sounds very likely to be positive to me.. as they normaly earth thru the bracket mount.
Connect the multimeter to the battery and give the car a few rev, see if there is any chance in the reading (voltage should be going up/increase) else if nothing happen or valtage drop if head lights are on, time to have new alternator..etc
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Re: should the alternator be earthed?

Postby l1ttle_d3vil » Mon May 30, 2005 9:09 pm

All_Fours wrote:are those 3 wires all reasonably small ones in a 3 pin plug? if so, then that bolt/screw that you're talking about is the output of the alternator, and should, as already mentioned, run into your fusebox to a big fuse (around 100A). Without that connected you will get no charging from the alt.
And unless the alternator bracket is made of plastic, it will be earthed very well so don't worry about that


yea, all those three wires come from a three-pin plug in the back of the alternator. i'll try get a pic of the plug and the bolt tommorow night and upload it...i'll check out some of the stuff mentioned here already though.

also, the battery isn't fully charged to start with.
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Postby Malcolm » Mon May 30, 2005 9:31 pm

in that case the bolt you're talking about is almost certainly the output terminal of the alternator, and needs to be either connected to the fusebox, or straight to the battery + terminal if you're lazy
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Postby l1ttle_d3vil » Mon May 30, 2005 9:51 pm

seeing as the 4age is in a ke35, can i just run it straight to the + terminal with a fuse somewhere along the wire, sthat'll do the same thing won't it? might be easier than running it to the fusebox and back.

but also, ive already got a power wire from the battery going into the 3-pin plug on the back of the alternator. why do i need 2 power wires from the battery? or is one for the reg and one for the alternator or something liek that...?
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Postby Malcolm » Mon May 30, 2005 9:54 pm

yeah one of them is for the regulator I believe, the big chunky one that comes off the bolt (use atleast 8 gauge, preferably 4 gauge wire) actually does the charging. You could run it straight to the battery with an inline fuse (100Amp).
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Postby l1ttle_d3vil » Fri Jun 03, 2005 6:56 pm

ive run a wire from the battery to that terminal and the battery is showing a voltage of 14.1 to 14.3 now so its all good.

will an 80amp fuse be sufficient? ive already got one of them lying around...
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Postby Malcolm » Fri Jun 03, 2005 8:07 pm

yeah it's pretty unlikely that your alternator can charge more than 80 amps. If it blows, then you can get a 100 amp one.
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