Curious Alternator issues (charging)

[Lambolica]

I'm having some strange issues with the voltages in the Corolla. At first I thourght it was the alternator going but I have swapped it for another unit and the Issue is still there.

The problem I am having is as follows:- when I start the car the voltmeter reads 11.5 - 12.5 volts (depending on battery charge) During this time the power windows don't work, lights are dim etc. After a few minutes of driving the voltage jumps to 13.5 - 13.8 and everything works as normal. After alot of driving the voltage starts to flutter between the High and the low voltages mentioned.

I spend a few hours pulling off all of the earths and cleaning and doing them up again and the symptoms were still there. Battery was replaced Symptoms still there. the alternator was replaced problem still there (however less frequent fluttering of voltages)

Since then the second alternator has been put on another car and works fine, So I am at a loss as to what the problem is. I have also looked at the wiring around and fused but can't find any damaged or problem wiring.

The alternator is an internally regulated type so id there any thing external to the alt that I am missing?? The engine is a 1G-GTE.

[Cool1]

There should be an ignition wire going to the alternator. If possible, disconnect this wire from the alternator and make sure you have +12V on it when ignition is on.

[Lambolica]

Can do... If it isn't would that indicate an issue with the ign relay, or some poor wiring in the cabin? The wiring in this car has quite a few gremlins that I'm working through 1 at a time, most are simple but this one is a pain...

[Cool1]

I'm not sure how your car is wired, but normally that ignition wire goes directly to the ignition switch.

[Lambolica]

I don't know how this car is wired.....

So Normally on a factory car this wire should run through the Body loom to the engine fuse box collection of plugs then out the Alternator?
I don't think this happens in my case. I shall check into it.

[Cool1]

Yep normally the body loom would connect an ignition source to the alternator.
What engine is it you have?

[Lambolica]

1G-GTE in an Aus spec AE-86. I'm sure the stock engine had an externally regulated Alternator. But when the conversion was done a JDM loom may have been used. (or at least partally used)

[Cool1]

See how you go and if need be i'll try and find a wiring diagram to have a look at.

[Lambolica]

I have a look at it when next near the wiring, I've chased the wire using wiring diagrams and the majority of the wiring is similar to the 1g-GTE wiring as best I can tell. there is some dodgy stuff under the dash however that I have been cleaning up.

The other thing that I forgot to mention is that the issue seems to be temp related as the car warms up the issue goes away and the flutteing has occured when turning corners or going over speed humps So you could well be on the mark there Cool1 with issues with a loose or poorly connected wire.

[Cool1]

The temp related part is interesting Could be a dirty/greasy connection somewhere and the heat lowers the resistance. But yeah I would be following the wire/s through and triple checking the connections.
It could possibly even be a wire that have been stretched and broken internally.

[Lambolica]

If that ign wire isn't running +12v I am guessing the alternator doesn't switch on to put a charge to the system?

This seem like a most possible cause then, I was looking for a problem between the battery and the Alt. and I have exhausted the rest of my limited knowledge.

[myne]

Hrm. You mention that it had an external regulator - does it still?
Voltage fluctuations could be the alternator, which is natively AC doing weird things with the DC current.
I cant help wonder what difference a Diode between the altenator and battery would make.
If I'm right, the fluctuations would stop but the alternator would only provide half its potential charge. That's ok though, because atleast it gives you a starting point.

[Lambolica]

No it now runs the internal regulated Alternator. What I'm unsure of is weather the body loom is the original loom or if it is either the JDM 86 or the Soarer loom modified.

This car has had some decent work done to it to get this engine in, whilst most of the mechanical work is top notch. I feel there were some short cuts done in the wiring department.

[Cool1]

Yeah if that ignition wire is not making connection, the regulator wont regulate.

[oldcorollas]

make absolutely sure that the alternator mounting brackets, between block and bracket.. and bracket and alt.. are clean, free of paint, and done up tight....

loose bracket will definitely cause these issues.. as would a broken charge wire to battery (or if original, to the starter motor wire and then battery) replace with brand new wire to battery??