More Alternator/Regulator woes

[taz]

Hi folks,

Hoping someone can help...

My ignition/charge light remains on constantly. Whilst running I only have about 12.3v across batt terminals.

I think my problem is that the alternator field windings are not getting enough voltage...

When I try the test cct as outlined in the manual, with one side of the alternator field winding shorted to earth, the other still connected to the regulator F terminal, the light goes off and I get 13.9v and about +40amps@3000rpm!!!

The 4TR regulator has been replaced with a 3pin bosch unit (D-,D+,F). The F regulator pin has the brown/purple wire together with the brown green wire soldered together (not 100% sure of colors though - it's hard to tell!)

The 6RA field isolator relay appears to be bypassed.

Using an ohm meter, I know that both alternator field terminals are connected to the regulator, one to F the other to D+ (batt voltage all the time on this one). However when running, there is only about 250mv across these terminals and therefore the field windings, both being close to 12v.

Should the regulator drag down the F terminal to increase the voltage across the field windings? or should on side of the field winding be connected to earth?

I thought it was the regulator, however I was given a replacement by my local auto electrician (bosch RE57) and the same things happens. I'd drive the car down to him to get it fixed however it's still unregistered.

Any help greatly appreciated!
Cheers,
Steve.

[Phil Nottingham]

I am not 10% certain as alternators are "electronics" which I do not do but but as to basic circuitry I alwys thought one side of the field winding should be connected to earth.

These set-ups are very simple and reliable so you should be able to sort it cheaply. Its usually he brushes that waer (one of them actually so just swap them round) Yours sound OK

The field isolating relay is a standard singelpole relay which any acan be substituted and is there to protect the ignition switch so relace it ASAP as it will soon overload it as evidenced by warming up/ missfires and poor starting.

You can of course substitute with a modern high output altrnator and dispense with all the regulator/relay/warning light can - see earlier threads

[taz]

Thanks Phil,

Another question...

What sort of amperage should the amp guage show A) when at idle with no accessories on, and B) 2000+ rpm again with no accessories?

From why I've read so far, it does seem that the voltage on the F terminal of the 4TR regulator is meant to be reduced (more specifically, the solid state cct switches it to earth very quickly many times a second) as demand for alternator output increases. And therefore neither of the alternator field windings are earthed.

I think other regulators can work in the reverse, eg the ones that have one end of the field winding earthed.


Cheers,
Taz

[Phil Nottingham]

Well as I said I am no electronics expert but what I did mean was that the regulator earthed it as you say. Its not earthed directly

As regards you readings queries.

a) The car ammeter is not a very precise instrument and should not be relied on at all for accurate testing purposes
b) The amount of charge is wholly dependent on the battery condition and at 2000 revs should not even show much at all if fully charged, and at idle with only the coil drawing it may just about keep up with the demand but again it depends on the idle speed - it should be about 600-650 rpm.
c) Switching on a load such as the lights will cause a brief filck up charge then it will settle down again to the steady state of just a little hardly noticeable on the car gauge.

The proof of charging if if the abttery goes flat!

Hope this will be of help

[taz]

I think I've got sussed...

I tested the regulator with a variable DC supply to the D+ terminal and earthed the D- terminal. I found that the F terminal voltage would follow the supply voltage very closely up to about 14V. If the supply voltage when higher, the F terminal dropped sharply to around 5V.

So I then removed the F+ spade connector from the alternator, which was permanently connected to batt voltage, and replaced it with a connection to ground. I left the alternator F- terminal connected to the regulator F terminal.

Now the system appears to be working, ie I'm getting around 14V from the alternator at idle and at higher rpm's. The dash amp meter shows about +5 to +20amps (the battery has low charge), so I'm hoping thats pretty normal.

I have no idea why it was wired up the way it was. It's almost like it was wired up for the lucas 4TR regulator which is not suitable for the bosch regulator.

Cheers,
Taz.

[Phil Nottingham]

That is the problem with using non-standard items - the 4TR is readily available over here I picked up a brand new one at a car boot for £3! They turn up on Ebay quite often too as well as from the usual suppliers.

It does seem like yours is OK now although 14v is a shade low and once the battery is fully charged it shouldl settle down to give the low steady readings and if its OK after that I would leave it.

As I mentioned you must reinstate the relay, any heavy duty one will suffice, to take the load iff the ignition switch which is overloaded at the best of times without the alternator field supply gong through it.

Old ignition switches can cause many strange problems and the sure sign its on teh way out is if it or the key getting warm. The column mounted switches are better than the console type though.

[taz]