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Alternator Output Issues


Yowzer
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RIGHT if you people can throw ideas and ways of testing things at me that would be great.

Here's the story. MS110 Crown, MEU engine. The factory alternator was missing so I fitted a unit off a '85 5MGE. Internally regulated, standard Toyota jobby.

The car was originally lacking the Sense wire so I simply hooked up the IG and L, and all was groovy. Rolled like that for a year or so.

The car then received 400W of headlight and 800W of amplifier. Potential for 100A current draw with highbeams on and stereo cranked to earmelting levels, but that's basically peak.

Alternator is a 60 (I think) amp unit. However it wasn't charging the battery.

Keegan took it into the auto sparky, who said it check out fine. I then figured it probably wants a sense wire now that it has a bit of extra load on it, so hooked on of them up but still no difference.

Battery would still drain while driving.

He took it back, they replaced the reg and diode pack, but still no dice. It'll put out around 17 amps at idle, and sit around 13V with no lights etc on, but when the engine speed increases output drops to under 10A.

Turn on headlights and whatnot and the battery volts keep dropping.

According to the sparkies, the alternator works fine, everything seems to be functioning fine, but it won't put out any more than 17-18 amps.

Any ideas on what to look for, how to test things etc etc?

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i would be checking for a voltage drop is that voltage at the alternator or the battery ?

also slipping fanbelt which im sure you would have checked an alternator should charge full out at 14.6v.

now the sense wire should be connected to the fuse box or directly to the battery not to the back of the alternator it works by detecting voltage drop in the cables so if you have 0.5v voltage drop in the alternator lead the alternator will put out more voltage to achieve 14.6v at that point so it may read 15.1 volt at the alternator.

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Yep sense is direct to the battery, voltage drop from alternator to battery is around 0.2-0.3V at 20A, belt is fine etc etc.

By the sounds of it, the slipring (which the sparky apparently checked) is oval instead of round, which is bouncing the brushes off them. Hence why the output has been dropping as the alternator speeds up.

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sounds like that could be an issue ive also seen corrosion on the batt post to the rectifier inside the alt which gives the same symptoms easy wat to check this is run the car for a while with lights on ect and see if the alt post gets hot otherwise courier the alt to me and i can fix it after all that is my trade

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  • 2 weeks later...
Guest chris r

If you want to bump the alts output a little, put a diode in the sense wire, The alt will sense roughly half a volt lower than the actual battery voltage so will charge higher than it usually would

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Guest Yowzer

It'll test to make sure the regulator is doing it's job anyway.

What had happened is the belt had glazed up and was doing very subtle belt b-owts which somehow both Keegan and I missed, until Keegan touched the pulley and burnt his hand.

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Guest flyingbrick

Hahaha that's gold. Just hose it with belt grip

I wonder how many keegans are in Hamilton. I met a keegan like three years ago in town- we were like best mates for an hour or two.

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Guest japawagons

Belt grip is the most useless fucking product I have ever seen for sale. Belts are designed to be properly tensioned period. Bust that bad boy out on your myth busters thread.

Hamilton is full of Keegan's, I grew up being the only one and now there's an epidemic. Even girls named Keegan. WTF indeed.

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Guest Steelies

i'm gona jump in on this thread,

my starlet alternator (4age) is over charging even with the ign, sense and light wires disconnected. first port of call was a new regulator, still mega overcharging. more RPM, more volts. haunted?

just whacked the multimeter on there now and had a poke, got continuity between slip rings and rotor shaft. i'm inclined to say this isnt right but i'm not very good at this electromagical business. got a brand new regulator in there and brushes arent bad. theyre worn in but not worn out, heh. replace anyway?

any thoughts?

ta

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Guest flyingbrick

Belt grip is the most useless fucking product I have ever seen for sale. Belts are designed to be properly tensioned period. Bust that bad boy out on your myth busters thread.

Hamilton is full of Keegan's, I grew up being the only one and now there's an epidemic. Even girls named Keegan. WTF indeed.

Belt grip is magic in a can. I had a slipping timing belt once on a 4age and belt grip fixed it in seconds without even needing to take the covers off ( just sprayed into a hole)

On a more serious note- until meeting that other Keegan- I didn't even know it was a real name

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