When the car runs fine i tested voltage drop across the battery, 14.4V
When the battery warning light comes on, tested again and read 12V
(but i guess the warning light is already telling theres a voltage difference but i just had to be sure)

Great, so dieing alternator...

But i have a gas installation, and theres heaps of spliced wires and connectors all over the place that are exposed and even rusting and maybe theres some dodgey connection (real long shot but if there is will save me heaps of money)

So i need to measure the voltage coming straight out of the alternator so i know for sure if its the alternator and just not some dodgey wire.

Now there are two cables coming out from the alternator, one is just connected with a bolt and the other is connected via a big plastic thingy.

So i put the positive of the multimeter to bolt and the negative to the metal frame of the alternator and got a 14 volt reading (warning light was off)

I couldnt get the warning light to go back on so i didnt get a reading for that but my question is, is that how you test the alternator? (confused about the whole metal casing of the alternator being negative)

and what is that cable with the big black plug for?

The one to the bolt is the output of the alternator, it goes directly to the positive (+) terminal on the battery via a fusible link. It's the one to measure the charge voltage.
The other wire is to the "charge indicator" light on the dash, my diagram shows 3 white wires to this connector.

Do you have a four or six cylinder, I could look in my earlier manual if I can find it.

Oops, didn't look at your profile first. V6 eh
My Haynes manual refers to the charging diagram as "typical" don't know if i can believe it totally but the big cable definately goes to the battery

woops, i dont know why my profile says that, ive got the 4 cyl.

Do you measure the output of the alternator by putting the positive of the multimeter on that bolt and the negative just to the metal housing of the alternator?

Yes, that will reassure you that the alternator is working if the voltage is higher than when the engine is stopped.
Another way is to put an ammeter (60 amps) not the one built into the multimeter between the big wire and the bolt terminal on the alternator.
If it's an intermittent problem I would be looking at the cable that goes to the black connector. check for corrosion.
Hope that helps?

yeah, when the car is fine the volatge is around 14 but when the battery warning light comes on its only reading the voltage coming out of the battery. So unless theres a dodgey cable somewhere its the alternator dieing on me right?

Now if im going to have to pull this one out and put in a new one i might as well try and fix the alternator myself, how hard could it be to pull apart the alternator and look inside to see whats wrong?

ill check for corrosion first but, thanks.

when my alternator started showing the warning liht at random times, it was cos the brushes were worn...

take the voltage regulator out and have a look... cheaper to replace the brushes than the whole alternator

also another common problem in alternators is the voltage regulator dieing... or one of the diodes not working... but it just sounds like worn brushes (or maybe voltage regulator if the brushes are fine) to me

Well when i get a chance im going to pull the alternator out and try and pull it apart and have a look inside, if it is worn brushes where do i get these to replace em with, just from repco or something?
How hard is it to pull apart an alternator?

Also does anyone know which alternators fit the TR, if i go to a wreckers what model magnas can i pull one out of, just the 2nd gens?

I wouldn't bother with a second hand alternator, it will probably do the same thing in 3 months.
If you alternator isn't making any bearing noise then the problem you have with the charge light coming on sometimes, will probably be properly repaired if you just replace the alternator charge regulator as bcx7 suggested. It comes complete with new bushes and is the black plastic box on the back of the alternator that the black wiring plug clips onto.
It is held to the alternator by 2 flat blade screws.
A replacement genuine Bosch regulator can be anything between $30 and $60 ($40 is a fair price) depending on where u shop and if you can get trade discount.

Note: the other larger wire between the alternator and battery +, is live 12V + when the battery is connected.
In most cars negative is via earth, meaning most metal parts of the car and engine as well as the alternator body are negative charged. So if a + wire touches any bare metal in the car it will short out. There is also earth cables between the battery - and engine/body that will affect charge if they have bad contact. (this would also slow or stop the starter motor)
To prevent shorts or getting DC burns, Disconnect battery before working on the alternator.

okai well im going to place the alternator charge regulator, something i can pick up from super cheap auto? repco?

okai well im going to place the alternator charge regulator, something i can pick up from super cheap auto? repco?
Repco or possibly cheaper from an auto electrician or local parts shop

I replaced the alternator in my '91 KR V6 recently after a wild goose chase.

In October last year it became noisy and the auto electrician I took it to replaced the bearings and regulator. All was fine for a few months and then it developed an intermittent charging problem. I took it to a different auto electrician (I had moved towns since the first one), and they checked it and said everything was ok. Fitted it back in, and still had same problem. I think I must have checked every single wire in that car before I called another electrician. In the end it turned out to be some faulty windings in the alternator or similar. Still not absolutely sure.

We priced a genuine one, which was around $1200 from memory. Looked around for a reconditioned one, which was about $350ish? Was going to go for that when a supplier suggested that the Hyundai Excel (not sure what model), has a similar alternator setup, something about the engine having the same external running gear. It was only $50 more for a brand new one. Thats what I went for.

okai well im going to place the alternator charge regulator, something i can pick up from super cheap auto? repco?

Better you try East Coast Auto, or Bursons etc. No it isn't something Supercheap will stock off the shelf. I have the same problem with the magna I just bought, it is pushing 16.68volts at the altenator and 14.36 at the battery. This is too high. You can also tell if it is charging too much, look at your battery and see if it is wet on the top ? If it is that means the altenator is over-charging it and the battery is boiling like when pluged in to charge on mains power. All the wetness is the condensed vapour. I get this after every drive the past week, so going to pickup a new regulator tomorrow. Look for signs etc first, and use a multimeter etc. My car even with headlights on highbeam etc, it still gets 14.36 shuved into the small battery. This really should be around 13.4 to 13.9 volts. Higher is not beneficial, rather harmfull. Battery won't explode, it will just kill it very very fast.

Regards,

Joel