Alternator

[ShaunAFC]

Ok, have fitted a 'new' alternator to the terrano.

Engine on and only get 11.8V across the battery. To me that says alternator is duff, wondering if anyone knew any other tests I could do?

Checked continuity of both earth and live to the alternator, no resistance in cabling so a good circuit.

Checked voltage drop on both earth and live, earth gives 0.2V and live gives 0.5V, both I think are ok. Checked voltage on alternator terminals and still only 11.8V.

Turn engine off and go across battery and 12.5V.

Is there anything else in the circuit that would stop the alternator sending charge back to the battery??

I am really being tested by this truck now. losing the will to fix it!!

 

[rustic]

Hi Shaun, alternators require a field voltage, this is normally supplied by the ignition warning light bulb, in the panel, when the voltage generated by the alternator exceeds the 12 volt supply, the bulb goes out and it is then self supplying.

So check the bulb and the circuit to the alternator.
Hope this helps.
Best regards, Rustic

 

[ShaunAFC]

take it that is the red battery jobbie.

Guess what.................no light even with engine off ign on!

I will become a priest at this rate, patience levels increasing..ha ha

Prays that it is the fuse

 

[rustic]

take it that is the red battery jobbie.

Guess what.................no light even with engine off ign on!

I will become a priest at this rate, patience levels increasing..ha ha

Prays that it is the fuse

Sounds like we are on to it.
To prove it, get a 5 watt side light bulb, connect one side to the + of battery, other side to the terminal on the alternator, this should act as the ignition lamp, and extinguish when the alternator is working then you should have a charge voltage. Then maybe replace the bulb in the dash.
Regards,
Rustic

PS your old alternator may not be faulty after all......

 

[ShaunAFC]

Rustic,

Bear with me there is more, just uploading pics

I take it this is the connector to the said bulb:




Also where should the light be on my dash, because I shine a torch at it and cant see where it could be!!

 

[rustic]

Shaun, yours is different to mine so it should be in the electronic manual.

See the link:

http://bebrs.pie-dabas.net/Webs/Terrano/R20/fwd.pdf

I will be away from PC for a while now..
Good luck
Rustic

 

[ShaunAFC]

Cheers for the help so far bud

 

[ShaunAFC]

OK established that the battery light should be next to the door open indicator. Guess I'll be having the dash out again then.

I take it, its one of the soldered jobbies, if so where do I get a replacement?

 

[Timbo_1975]

With Ign Light wire grounded in engine compartment (disconnect from alt) and key on, you should have the warning lamp lit.

If you lash up a 5w bulb between +12v and alternator excitation terminal it should light straight away. Starting engine it should go out as alt begins to charge. Bat voltage should go upto ~14.2v indicating the alt is charging.

You should have +12v on the thick supply wire at the alt. Careful you do not short this to ground.

Doing the above tests should easily identify where the problem is..

Tim.

 

[ShaunAFC]

Ok, i take it the excitation terminal is the one I identified in the pic?

Is has two pins which should i connect to?

Many thanks

 

[Timbo_1975]

Without looking in the wiring diagrams, the thinner white / blue one I would suggest.

 

[ShaunAFC]

Hey if you want to have a quick look its on page 24.

http://bebrs.pie-dabas.net/Webs/Terrano/R20/sc.pdf

 

[ShaunAFC]

Well, the bulb and holder work fine, BUT not in the battery position.

I will explain.....take the bulb oout of this position and swap it into the side lights/dash illumination position and works no problem, put it back in the battery slot and it doesnt work!!

I have the horrible feeling that it may be the track on the PCB, but it all looks good. Going to have a look at the wiring diagram and see where the bulb takes its supply into the console and where it feeds back out, maybe I can spice into the loom and insert a bulb possibly mounting on the dash?

Any opinions would be greatly appreciated.

 

[rustic]

Well, the bulb and holder work fine, BUT not in the battery position.

I will explain.....take the bulb oout of this position and swap it into the side lights/dash illumination position and works no problem, put it back in the battery slot and it doesnt work!!

I have the horrible feeling that it may be the track on the PCB, but it all looks good. Going to have a look at the wiring diagram and see where the bulb takes its supply into the console and where it feeds back out, maybe I can spice into the loom and insert a bulb possibly mounting on the dash?

Any opinions would be greatly appreciated.

Hi Shaun, it could also be the connector, sometimes the pins/sockets pushback into the housing(s), but if you do test the security of the connectors don't use anything metal like a screw driver, use an insulator, eg plastic rod or small wooden stick, children's paint brush handles are good for this.

I assume then that bypassing the bulb has enabled the alternator to charge now. As this was the main objective.
The feed for the ignition bulb needs to come from a feed that is live when you turn the ignition on, otherwise you will drain the battery if from a constant feed.

Best regards, Rustic

 

[ShaunAFC]

It gets even more interesting, upon taking bulb holder out measured the voltage across both sides of the track, i.e either side of the bulb connector, with IGN on engine off.

Get +11V on both sides!

Now feel free to correct me, but in order for the bulb to light, one side needs to be at 0V while the other is at 11V, therefore creating a path to flow.

I thought that when you turn ign on, bulb lights as it is getting no return from the alternator, turn engine on and when alternator starts to charge it gets return and therefore extinguishes as it is in the equilibrium status which I already have with just ign on!

Reall dazed and confused here.

I have not tried the bypass yet as I did not have a 5w bulb to hand, I an 99% convinced that the bulb scenario is to blame though

 

[rustic]

The scenario you describe is the same as if this alternator was faulty as well, if you disconnect the alternator the voltage will disappear at the panel.

Re: testing the alternator.
If you haven't got a 5 Watt bulb a 1-2Watt like from the panel light will suffice.

Where did you get the alternator from?

 

[ShaunAFC]

West lancs auto elecs, maybe I have a lemon!

 

[ShaunAFC]

Thank you again, another day spent on the terrano then..............

 

[ShaunAFC]

OK, positive from battery to one side of bulb, excitation terminal to the other

IGN off - bulb is lit.

Disconnecting the bulb connector from the alternator still left me with 11V both sides on the console!

 

[ShaunAFC]

Ok connected said bulb, +12v from battery one side and excitation terminal the other

IGN Off = bulb lit

Ign on = bulb lit

Eng on (battery is pretty flat) = Bulb on BUT voltage across battery raises to 13.5v