Alternator???

[DaddyA]

Hi all,

this is a carryover from my engine thread so apologise all round.

Just to refresh, my battery charging light didn't work, consequently my alternator wasn't charging!!

Spent hours today with the electrickery and still no further on, I have got the charging lamp to illuminate by taking a switched live to the lamp.

I did get the alternator to charge by supplying the relay with a different supply, however when I switched on the ignition the alt light went out??? Then when i started the engine the fuse blew for the relay??

Am i missing something here?? Not fully conversant with car electrics so any help would be appreciated.

In the end I had to walk away and put everything in my hands down before i caused some damage

Hopefully sort it soon though.

[twinturbo]

check everything is ok with the alternator by simply putting a bulb in-line between +12V on the battery and the charge output post on the alternator

TT

[Enoch]

I had exactly the same problem with mine, I found it was teh bulb holder not making proper contact with the printed circuit of the instrument panel. I cleaned it up and put a dab of solder on to the pads where the contacts of the bulb go and it now works perfectly.
hope that helps,
Enoch

[DaddyA]

Thanks for the replies,

I'm pretty sure its not the bulb, no printed circuit board to deal with.

I'll try the lamp in line, I think its wired wrongly but I'll keep going till something happens!

just to clarify,

large red to battery, one wire to warning lamp fed by 12v switched supply and other one fed from alternative 12v supply?

[twinturbo]

????

Which engine is this from? I know CVH's have 3 terminals.

the two fat red ones go direct to the battery +12V
the small blue one is the charge lamp.

Rule out all other elements of the charge lamp circuit by removing it and replacing it with an inline lamp back to +12V on battery as described.

We can work from there once we have confirmed the alternator is working.

TT

[DaddyA]

Cheers TT,

its 1.8CVH, it did charge briefly so it does work, it just kept blowing fuses.

I've only got one going directly back to the battery, one to the chrging lamp and the other goes via relay - this where I think the problem lies but if that one can go straight to the battery then that should sort it - hopefully.

However, when in that brief moment it was charging, the engine wouldn't stop (it was mentioned I'd need something inline to stop this).

I won't be able to tweak today as we are entertaining but I'll have a look tomorrow and let you know how I get on.

[DaddyA]

Hi,

well managed to get in the garage and have a look.

3 terminals on alternator. (1)Large red to battery. (2)Middle terminal goes to warning lamp. (3)Last terminal goes to relay?

Have have put a bulb between 2 and battery - lamp illuminates. Same with 3.

Connected 3 directly to battery and wired up 2 with a power supply.

Position 0 & 1 on ign and lamp illuminates, position 2 and the lamp goes out.

Position 3, engine starts and alt kicking out 13.5+ volts.

When eng stops, battery warning lamp back on, even with key removed.

Getting there, slowly. Smaller cable to battery seemed to get warm???

[twinturbo]

is the lamp connected to the black and yellow wire on the ignition switch?

TT

[DaddyA]

Originally Posted by twinturbo

is the lamp connected to the black and yellow wire on the ignition switch?

TT

No, at the minute it is just connected to another switched supply.

[Land Locked]

take a look here http://www.locost.co.za/forum/viewtopic.php?f=6&t=1729

and this is my preferred alternator light arrangement


When O posted this on the Sarf Effirken forum I was asked what the diode was for. This was my response:
I cribbed the circuit off a VW Instrument cluster. I was in a hurry and not overly interested in why it worked only that it did in fact work. It was for use on a drilling rig going into deepest darkest Africa, so all that mattered was that it worked well AND reliably. In the years I was with VW and Audi we never had a charge light failure that was related to anything on the circuitry on the cluster. In my eyes that's a pretty reliable circuit. Several years later now and I've had no comeback from those drill rigs.

Now as to some quick thoughts as to why we have a diode in the circuit.
1.The W or D+ terminal does put out a voltage when charging, so I think the diode is simply a blocking diode to prevent a backfeed.
2.LED's don't like reverse voltage. Reverse voltages as low as 5volts can cause them to self destruct.
3.It may not even have been related directly to the charge circuit.

Component values:
The 1n4007 can be almost any diode rated around 1 Amp.
The 820 Ohm resistor could be any quarter watt or bigger resistor between 680 and 1200 Ohms, it only prevents the LED from self destructing.
The 100 Ohm resistor could be anything from about 90 to 120 Ohms and at LEAST 5 watts (10 or 15 would be better), any lower on the wattage and heat becomes a HUGE issue. I have measured lower wattage resistors getting over 200 degree's Celcius.

Feel free to post any other questions, we all benefit from them.