Tahoe E Fan Problem! Help

I have a Tahoe e-fan set up in my 99 Sierra RCSB with the relay's from Nelson. They have been in the truck for obout a year and a half with no problems. Now I am getting a 2 amp drop when the fan kicks on in defrost setting. My battery is also not starting the truck over night.

I have a 100 monthe diehard gold battery that was installed in May of 2008. The battery charges back up fine.

Could I need a bigger altonator so the charging system can keep up?

Maybe do I have an issue with my Nelson e-fan harnes?

What amps are the stock altonators?

Thanks in advance. Mark

Have you had the battery and the alternator checked? I would start there 1st.

I am going to do that today. Thanks for the response.

How are you measuring a 2 amp drop?

When the fan kicks on my guage is droping down to 12 at idle. when I am driving down the road and the fan kicks on the lights dim and the truck feels like it stumbles.

That's voltage, not amperage.

Sorry I meant 2 volt drop.

Does your battery, allow you to check the water? Could be low. Otherwise the battery is toast, trade it in.

It may not be the fans of battery but the ABS module motor stuck "on". Those modules are notorious for that and will drain your battery overnight.