Alternator problem

[Yareck]

Some time ago I replaced my old alternator with a new one. Ever since I did that I have to rev my engine up to 2500 rpm's for it to kick in. So every time I start my engine I have to do it in order for the batteries to charge. I called the producer and they told me to check the power with ignition on with a multimeter on those two wires that are on the back. One is purple another is red. There's no power on the purple one.
Any idea what can it be?

 

[Boater420]

I'm thinking you don't have the exciter wire in the correct spot. The exciter wire energizes the voltage regulator and tells it to start producing electricity. I'd start there. The purple wire should come from the key switch run position and go to the exciter terminal.

 

[sibnai1]

If you haven't already, make sure the tension on the alternator belt is within spec.

 

[Yareck]

Ok I'll check my key switch first

 

[Yareck]

I checked the ignition. Everything is connected like it should but still no power. Where else this purple wire ends ? Maybe I should look there?

 

[Boater420]

Are you getting 12v from the key switch on position? Test with a multimeter to make sure. The purple wire starts at the key switch (ON) position and ends at the alternator's EXC terminal.

 

[Yareck]

I did checked. No power on purple wire when the key is in on position.
There are 2 purple wires connected in the same spot to the ignition.
I don't get it . Everything worked ok until I replaced alternator