Wiring help

[redcube]

I need a bit of help with wiring from the back of the alternator.
On the back of a mk3 or mk4 alternator what are the three wires doing and what color they are?
On the back of a mk5 alternator what are the three wires doing and what color they are?

Thank you

[Timbo]

On the mk3 alternator you will have three spade connections, 2 large and 1 small. Two red wires go to the large terminals (connected together inside the alternator) and thin blue wire (from the ignition warning light) goes to the smaller terminal. The 3 female spade terminals on the wiring loom are usually in a black plastic "plug" that goes onto the alternator.

On the mk5 Diesel alternator (70 amp)there is a block with three studs that have nuts on. Looking at the front of the alternator, the left stud has a thick red lead and is the output. The middle stud has a thin blue lead to the warning light. The right hand stud may have a thin grey/black wire and is the pulse signal for the rev counter if fitted.

HTH.

[redcube]

On the mk3 alternator you will have three spade connections, 2 large and 1 small. Two red wires go to the large terminals (connected together inside the alternator).

Do the two large connections go to the + on the battery

[Timbo]

Yes they do.

[MrMPuk]

Yes they do.

You sure? Doesn't at least one of them go to the starter?

[redcube]

Ok the two go together that's why i am getting no charge I'll do that and see what happens in the morning

[Timbo]

The 2 reds are connected together and may go via the live terminal on the starter solenoid which is connected to the battery positive anyway.

It's a long time since I had my mk3...............

[redcube]

I have a mk5 with a mk3 alternator cause i had it in the shed and it works where as the mk5 one went up in smoke and melted the wiring

[dutchreimovan]

On the mk3 alternator you will have three spade connections, 2 large and 1 small. Two red wires go to the large terminals (connected together inside the alternator) and thin blue wire (from the ignition warning light) goes to the smaller terminal. The 3 female spade terminals on the wiring loom are usually in a black plastic "plug" that goes onto the alternator.

You should read instead of ignition warning light, loadwarning light.
Please also note the bulb itself, has a important secondary function as a resistor in the external part off the voltage regulating circuit! If the bulb is malfunctioning (exit?) or a wrong wattage, you will have loadproblems.

If the fieldvoltage of youre alternator (the blue wire) is less than 13Volt, the light stays on.
Upto 14.25V (loadvoltage), it stays Off.

Never: disconnect the redwires when your engine is running: you will most certainly damage your alternator!

Load problems: check your loadvoltage and fieldvoltage first!

[redcube]

Been at this all day still the same but know i have no battery light on the dash at all i had one once and it used to flash on and off then never came back so do i change the blub and if yes what type of blub is it.
Also i checked to see the output of the alternator on my van I'm getting 12.4V i put the same alternator in to my neighbors van which is a mk3 and I'm getting 14V so i dropped my battery in his van and it still reading 14V what is going on here

[dyte2004]

perhaps you have a ground problem somewhere

[redcube]

where are the earths the ones i can see are on the starter and one on the body

[Timbo]

Connect the thin blue wire to earth and turn the ignition on. The battery light on the dash should come on.

If it does then the alternator is the problem - probably brushes u/s.

If the light doesn't come on then you have a wiring or battery light problem. Try pushing the wiring plugs firmly into the back of the instrument panel.

[redcube]

OK I'll try that then

[redcube]

I have given up going to get a new MK5 alternator i only want to use the mk3 cause i have a new vacuum pump for it and my mk5 one was shot so back up and running next monday