JS
The line you are referring to is 100C.
I wound up using a 1.82k after trying a 1.5 for several weeks.
This gets the fans on at approx. 100C vs the stock 105/107.
I like this as they are called for only when needed. This also gives you a cut-out of about 95C.My car seems to run best in the 90/95 eng temp range.
The parts are available from RS

They have to be ordered , as they are RSU #s. { not normal stock]
1.5k -1% tol., metal film, 1/4 watt---RSU11345766.
1.82k-RSU11345774
5- pack/$.99

If you can't find them, email me and I will sent a few of each to
you.
You may like the 1.5k better, but I found that the cut-out point was too low and had what I considered to be a too long running fan time when not needed.

As far as the man. sw in the cabin- I have done this with Benz for many years and kinda like having that control. Beats putting the heat on......does have it's uses and gives you the jump on the temps..