HDD Fan runs at 5100rpm after new 2Tb install

Apple OEM HDD - Barracuda 7200.12 1000Gb

ST31000528AS

P/N: 9SL154-040

FIRMWARE: AP24

DATE CODE: 10124

APPLE P/N: 655-156A

REPLACED WITH - BarracudaLP 2TB 32MB INTERNAL KIT 5900

ST320005N4A1AS-RK

P/N: 9JB1AT-573

BACKGROUND

After a HDD failure I replaced my OEM 1TB HDD with a 2TB model following the replacement instructions at iFixit.

The step-by-step guide was flawless, until I re-started the iMac. After approx. 2-3 min the HDD Fan began to increase in speed from ~1100rpm to ~5100rpm (over a 10 period).

Right now iStat is reporting 5127rpm and HD temp of 108degF

There does not seem to be a definitive solution/fix on any of the other "solutions pages".

1. Other sites suggest that the cause is in the proprietary firmware that Apple uses on it's HDD to control the temp. Is this true? If so how do you get a copy?

2. Has anyone tried replacing the Thermal connector that plugs into the drive with the older "stick on" thermal sensor? If so does it work?

I was all set to buy a new HDD from Apple, but when the "tech" at the "Genius Bar" looked up the price -- $506.

tech-Do you know how to use a screw driver?

me-YES

tech-Then do it yourself, it's very easy, use the instructions at iFixit.

me-are there any limitations?

tech-just buy the same kind of drive...you have a seagate, so just go to BestBuy and pay $100 bucks, or even upgrade to a 2or3TB.

Thanks for the help