Radiator fan always on ?!?!

Hi. This is my first post but I have been doing a lot of research over the past 4 days. My 99' Blazer 4x4 seems 4.3L Vortec runs a little warm to me. My gauge reads one 'tick' below 210 which I seen is normal. Today I took the thermostat out to make sure it was functioning and it seems like it is. My problem is that my radiator fan stays on the time. Whether being just started or going down the road. The air is extremely hot coming off the radiator which doesn't seem normal but it is getting the job done. I have not had any overheating. My cooling system was power flushed last year due to clogging due to the Dexcool reaching the 110,000 mile marker. While they were doing that they changed the thermostat.

Anyways, I recently had to have my radiator taken to a local shop to get the seal around the oil cooler connection fixed. It had been leaking fluid slowly and causing me issues with always having to get it checked for fluid levels. Well that was a sucess. I have gradually been phasing out the Dexcool with the leak over the past 4 months to the point now where it is the fluid that is yellow. I am trying to work out the air bubbles.

I have read in one of those self-help books that the fan should spin but with some tension on it. If it spins freely then it is bad. My fan has tension on it which I turn it with the engine off. But it will spin up very quickly if my engine gets hot (a little over the 210 degree marker) and will spin up loudly for a while when I take off. The odd thing is my fan stays on at all times.
Is my fan clutch bad? B/c recently my alternator seems to have a strain on it until I move at highway speeds. 12.6v while idling and 13.2 while the engine is revved. It is below 12v at night and my lights dim. I tested it with a multimeter so I know it is charging fine, just a little low.

Sorry for the long winded first post.

On any fan cluth setup, the fan always turns....when the engine is running... kinetic energy alone will do this. When it gets "loud" is when it is actually kicking in. most of the time at road speeds the thing is just happily idling along. WHen it gets HOT, it kicks in to force air movement.
On a side note.... you should NOT mix coolants, especially different "colors"... they are actually coded that way. get it flushed and replace it with the proper recommended coolant asap.

I am not sure how much KE is needed to make the fan turn but there is some serious wind behind pulled thru the radiator.

On a side note, if that fan is operately correctly does anyone have a clue why my alternator is putting out low voltage like it is being strained?

Well you could have a bad alternator or possibly a bad battery that isn't holding a charge. the more electronic items you turn on the more you are going to stress out the charging system. You are likely to hear the fan and fan clutch "roar" when your a/c is on cause you are putting more stress on the engine and cooling system.

If the fan is roaring all the time, your fan clutch needs replacing.

This may be a back-to-basics thing, but check your belt tension too...