Possible alternator failing?

So I've been having this weird symptom for a while now and it's time I try to figure out what is going on. Whenever the auxiliary (electric) fan starts to run, the voltage gauge on the dash dips and if my head lights are on they momentarily dim. Is this a sign the alternator is failing, or could it be something else?

Thanks in advance!

Edit: 99 cherokee, 4.0L engine, Auto, A/C

Are you talking a big drop in voltage and a significant dimming of the lights? If not, I think what you're seeing is pretty typical. When the fan first kicks on it draws a lot of power. As soon as it's up to speed, voltage should return to just about normal.

fyrfytr1717 said:

Are you talking a big drop in voltage and a significant dimming of the lights? If not, I think what you're seeing is pretty typical. When the fan first kicks on it draws a lot of power. As soon as it's up to speed, voltage should return to just about normal.

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I would say it is pretty significant. To oncoming traffic it looks like I am flashing my lights to warn them of something. It's way beyond anything that would be considered "normal".

put voltmeter on battery and turn on all acessories running and see what it reads. should be 14-14.5 volts