UK Car Repair: Vauxhall Astra 1.7td isuzu 1992, vauxhall astra, alternator belt

Question
QUESTION: Hi,

I have recently changed the alternator belt and now the power is fluctuating. With the engine started i put a volt meter over the battery. The read was 12.1 volts. I turned on the lights, fan, rear heated window and the volts on the meter continued to drop. Im not to sure if this is an issue with the regulator and if so someone has told me thats built into the alternator on this model. Any suggestions would be a great help.

Thank you in advance.

ANSWER: If it was alright before changing the belt then I doubt it isd the alternator.  Check that; 1, you have the belt properly tensioned;  2, The belt is routed properly;  3, You did not disconnect any wires anywhere.

---------- FOLLOW-UP ----------

QUESTION: I had the issue before changing the belt but now since changing the belt the problem has become worse.

Answer
Still check for loose or bad connections, is the battery in good shape, with the voltmeter on it, disconnect the king lead and turn the engine over, it should not drop below 10volts.Otherwise it is the alternator, it most likely is more economical to get arebuilt unit but shop around.