1/2JZ Alternator issue supply at idle

[BMWTurbo]

HI Guys,

I'm trying to trace an low voltage at idle issue in my car. I've had the battery tested, and it's come up 'normal and charged' on the Excite battery meter.

The issue is I'm getting down to 10 volts when the car is idling. This will shoot up towards 14volts when the engine is revving though.

I'm thinking it's the alternator now as I did some testing yesterday After charging the battery for half a day and having it sit on a nice constant 11.5volts I started the engine and removed the battery post so the car was running off the alternator and 4amp charger. Car ran roughly at low voltage then when I removed the charger the engine stomped.

I'd imagine the 2jz alternator should ba able to supply 30-40amps ( to pic a number from teh air) at idle as otherwise you'd be draining your car battery at night with lights etc on.

I will also add this has only started happening of late and I first thought the battery, but am leaning towards alternator now after a couple of supra owners have said they get 14+volts at idle in thier supras.

Can anyone shed some light on this? I will be changing the alternator on the weekend, but it's a bit of stuffing around.

I have chacked all joints and connections and they appear fine. I'm getting the exact same voltage as the battery, 12volts post in the engine bay and output bolt on the alternator.

Thanks in advance.

[Norbie]

In theory you should never see much below 12v at any time unless the battery is totally knackered. The only time I've seen 10v is during cranking!

Where were you testing the voltage from? And what sort of electrical load was present at the time?

[JP]

tired regulator in the alternator?

[Just1n_mc]

Probably just getting low on brush's. Should be a nippon denso unit, there on nearly all Toyota's. You can buy the brush holders with brush's for like $12. That's almost always what goes wrong with denso units. Pretty bullet proof alternators otherwise.

As far as disconnecting the battery while it's running goes thats no way of testing the alternator. Most late model cars won't continue to run after it's disconnected regargless of the condition of the alternator.

When the alternator is working you should see between 13.4v and 14.4 at idle and at rev's depending of the charge of the battery.

[BMWTurbo]

That was my thinknig Norbie... Battery is fine, bar the fact it is getting lumped with supplying the 30amps+ at idle because the alternator isn't pulling it's weight. This also means that the battery isn't getting charged.

Voltage was tested at battery terminals (battery under rear seat), The front +12v binding post in bay, and the alternator output bolt. It read constant accross the three.

Load I have headlights on. I also had engine running with thermo running too so as mentioned probably 30-35amps total.

I haven't done anything with alternator. I'll just change it out as I have a spare and then look at rebuilding this one.

I didn't want to have to change the alternator for no reason is all

I've read tha auto 2j's have a larger alternator. I also have a 1jz auto alternator, but will have to compare ratings and plugs and I'll pick the best one

Has anyone had a toyota one rewound???

I'll also be looking at a replacement battery as a precaution, probably a DIN88 800CCA.

[chris davey]

I had my camry one rewound. Worked a treat.

Also, was going to get my 1jz one rewound as it sits at 14v at idle but gets below 12v at full noise.

[BMWTurbo]

Sounds a bit strange Chris... Why does it drop Voltage at speed?

[chris davey]

I had a suggestion that the belt was slipping but mechanic thought that the brushes might be going. I was going to take it out and get alternator shop to check it out for me. I don't think the belt is slipping though.

[EldarO]

1JZ alternators are a prick to change, id imagine 2JZ is much the same.

1J's have a habit of killing either alternators or power steering pumps, im guessing its having them mounted low is some sort of cause, as the 7M alternators are the same internally, but dont die as much as 1J units.

mine was dead when i got my halfcut, unfortunately i didnt find out till after i had the engine in.

the bolt was stuck and took 5 hours to get out.

Elmo.

[BMWTurbo]

Hrrmm howcome they are so hard to change? I've already undonw the large bolt on mine I used it for my engine earth. from memory there are a couple of other bolts and you are rolling...

After dropping serp belt off, shouldn't be too hard? Am I missing something?

[EldarO]

nah, im just a hissy bastard.

the serpentine belt is a bastard to get off and put on.

the big bolt is a bastard when its welded on with rust and salt, ive just had a bad experience

plus im comparing it to my other experiences, of 5SFE and 7MGTE alternators, both mounted on top of the motor.

Elmo.

[BMWTurbo]

Fair enough Elmo... Serp belt is literally a 2minute job with the right size socket...

The only bolts I have issues with on jz's have been manifold bolts, and the crank bolt... Everything else has been good as gold..

I do however HATE removing A/C compressors... if you think alt's are bad wait until you get to do a comp

[EldarO]

im just too unco to co-ordinate between swinging the serpentine tensioner and taking the belt off, i was amazed at the amount of tension behind the bastard!

Elmo.

[Ribfeast]

We had the AC compressor removed from my car in 10-15 mins, wasn't too hard...

Serp belt is a 2 minute swap, or a few seconds to remove really. Then 2 bolts and a plug and the alt is out. Getting the belt off (especially putting it back on) is really a 2 person job, unless you have pretty strong arms or a good lever/bar.

I'll be watching this thread with interest, my car sits on 11.5V at idle, measured straight from the alternator. Idles at 630RPM. Battery is fine, starts the car easily. I do have two 14" Davies Craig thermo fans wired to be on while the car is on, which doesn't help.
I suspect it is the regulator in the alternator, or just the alternator is not up to the task of supplying that much current at idle.
When the engine is above 1000RPM or so the alternator puts out plenty of voltage.

7M alternators have the same plug on the back as a 1JZ, and similar mounting holes, refer to the thread I made with photos comparing the two. I'd be interested to know if anyone has fitted a 7M alternator to a 1JZ.

Has anyone made an external regulator?

[BMWTurbo]

Well changed te alternator... took less then 30mins... Seems I have over 13volts at idle now on first testing, so will see how that pans out after a few days to get a baseline.

Brushes appeared okay, but they was grooving in the armature. I think it will need the armature machined back to true a new set of brushes and should be fine. Probably drop it in to someone to asses first.

I'm also thinking I'll change the battery as a precaution, an 880CCA one should be okay