Alternater Wireing

[Guest robert elms]

Hi all

 

Got a bit of a problem wired up the alternater 1 wire going to the starter motor and 1 wire going to the volts meter and then to the batterie dash display all works fine but once the engine is running the dash light stays on and does'nt go out as it should, here is a picture of how i have wired it up, the far right wire is going to the starter the middle one is the one going to volts and dash and dont know what to do if anything to other wire any help would be appreciated.

[Guest mcramsay]

is the alternator actually charging? as far as i know this is how the circuit works, you have a 12v lamp on the dash board, when you start the car up there is a potential difference across the lamp (12v going down to the alternator) this is the exiter current going to the alternator so it can start to produce a voltage, once it starts producing a voltage it should send 12v back up the exiter wire to the lamp, this means the lamp will be sending 12v to the alternator and the alternator will be sending 12v back meaning there is no potential difference which means the lamp should be off. if the lamp is staying on either the alternator isnt charging or you have a wiring issue some ware! wack a volt meter across the battery when the car is running and rev it a little, you should see between 13-14 v on the battery if you are below 12v or the the charging voltage doesnt increase when you rev the car then something in the alternator is goosed. or you have no exiter current!

[Guest boggybogstar]

mmmm, that would cause the battery bulb to stay on, Rob and me have been trying to get this working over the phone but he's meter is the kind that only tells if 12v is there (and I forgot to take my meter down last time !!) - this alternator came straight of Robs donor where it worked fine so although it could be knackered were kinda hoping not.

 

 

he has 2 other pins on it, one looks like it's never been used - and some alternators dont need the '3rd', they're marked B+ and D+, when we were on the phone together we tried a switched live on the B+ and wired the dash light to the D+ with a live feed the other side - light comes on but doesnt switch off - tried the other way round but doesnt work at all.

 

Any ideas would be great - this is the last of Rob's electrics.

 

Still dont think you'll be driving it to Newark this weekend though Rob

[steve in stockport]

I think you should be wiring it with the battery direct to the B+ terminal, the dash light should have a 12v switched feed in, then back out to the D+ terminal.

Take the voltmeter out of the circuit and use another 12v switched supply to power it.

[Guest robert elms]

Still have alternator probs if anyone has any ideas???

[Longboarder]

Can't make much of your picture. What alternator is it? What are the terminals labelled on the back of it? Are the thre terminals in the picture the only terminals on it? Have you a better picture of the back?

 

Nigel

[Guest bob13]

Is the diode ok? for the light, If not the light will light all the time or not at all. I have tried to explain how it works below, clear as mud......

 

When the alternator is running correctly it is positive. There is a diode letting this voltage pass this makes it positive on both side of the diode so no flow so no lights. When the alternator is negative ie not working, there is no voltage from the alternator. There is a negative, so the voltage will flow so the light will light.

In the pic the 3 small diodes do this.

[Guest robert elms]

I will try and get a better picture .

thanks mr bob but call me thick i no nothing about wireing so it is clear as mud do you mean the light on the dash could be faulty or the alternator could be faulty ?

[Guest bob13]

I will try and get a better picture .

thanks mr bob but call me thick i no nothing about wireing so it is clear as mud do you mean the light on the dash could be faulty or the alternator could be faulty ?

 

I believe that you can have a diode on the dash, has been a while since i have played with car electrics. May be worth just changing the rectifier pack on the alternator. Not normally expensive to do, and some alternators have a rectifier/brush pack so worth doing just as routine maintenance or fault prevention.

 

have fun

[Guest robert elms]

It wont let me post a picture up its saying its bigger than 500k the left one has b+ the middle has d+ the right one has w

[Guest bob13]

It wont let me post a picture up its saying its bigger than 500k the left one has b+ the middle has d+ the right one has w

 

At a guess, b+ battery, d+ Field ie 12v supply from ignition and w the wire for the light.

[Guest boggybogstar]

Rob - reading these posts I think your alternator is knackered, or at least the diode pack on it, must admit i was thinking this when we were playing on saturday but my only doubt was the fact it was working on your Sierra.

 

I have a couple of spare ones here you could try, one of them should be the same size so should just bolt on, the other might need a new fangled bracketry invention !- only problem is they havent got pulley on but your one should just change onto it.

 

Failing that it could be mr scrappy again for one

 

Let me know - I'm still planning on going to Newark this weekend but am around Thursday & Friday, I'll dig them out the shed and have a look in the morning

[Guest boggybogstar]

ps - posting pictures - if you have microsoft office ....

 

right click the picture file and go "open with"

select "microsoft office picture manager"

when the pictures open select "Picture" then "Compress picture" and select web pages on the right hand side

 

ok it and close it down and the file size will be below 500k so you can upload it.

 

if you havent got microsoft office then tough

[Longboarder]

b+ battery, d+ Field ie 12v supply from ignition and w the wire for the light

That should be right.

B+ to the battery positive terminal (via the starter on your car which is quite common) using a big fat red wire.

D+ a switched ignition live. This can be from pretty well anywhere that is only live when the ignition is on.

W wire this to one side of the ignition lamp in the dashboard. In the bundle of wires coming out of the dash pod it should be blue if you have a ford dash. If things like fuel gauge, oil pressure lamp are working then the ignition lamp already has its other terminal properly wired in. You can try this blue wire on the D+ terminal without risk and not use an ignition live at all and some alternators will work this way. Just the blue and fat red. Some won't and you need all three connected as above.

You are unlikely to have a diode in the dash that you need to worry about.

The fact the ignition light stays on means the light itself is not faulty.

I wouldn't assume the diode pack in the alternator is faulty yet.

Substituting a known good alternator is a good idea.

If non of this helps you may have made an error in the wiring of the voltmeter and you could try disconnecting it and carefully insulating it's wires as they will be live.

 

Nigel

 

Checking across the battery terminals for about 14(+ a fraction) volts while the engine is running using a hand held voltmeter would be a good plan if you can get hold of one. You might find the alternator is charging but the fault is with the wiring of the ignition lamp.

[Steve Walker]

That should be right.

B+ to the battery positive terminal (via the starter on your car which is quite common) using a big fat red wire.

D+ a switched ignition live. This can be from pretty well anywhere that is only live when the ignition is on.

W wire this to one side of the ignition lamp in the dashboard. In the bundle of wires coming out of the dash pod it should be blue if you have a ford dash. If things like fuel gauge, oil pressure lamp are working then the ignition lamp already has its other terminal properly wired in. You can try this blue wire on the D+ terminal without risk and not use an ignition live at all and some alternators will work this way. Just the blue and fat red. Some won't and you need all three connected as above.

You are unlikely to have a diode in the dash that you need to worry about.

The fact the ignition light stays on means the light itself is not faulty.

I wouldn't assume the diode pack in the alternator is faulty yet.

Substituting a known good alternator is a good idea.

If non of this helps you may have made an error in the wiring of the voltmeter and you could try disconnecting it and carefully insulating it's wires as they will be live.

 

Nigel

 

Checking across the battery terminals for about 14(+ a fraction) volts while the engine is running using a hand held voltmeter would be a good plan if you can get hold of one. You might find the alternator is charging but the fault is with the wiring of the ignition lamp.

 

I think that on most (all?) alternators, W is an ac output from before the diode pack and is frequently referred to as the "tacho" output.

 

On most alternators, the field connection is fed from the dash lamp and there is normally no switched feed to the alternator, other than the dash lamp.

 

So, I'd say it should be B+ to battery+, D+ to dash lamp, other side of dash lamp fed from switched 12V, W should not be connected.

 

SteveW

Edited June 17, 2009 by Steve Walker