More reliable IMO since every part is external and replacements easily sourced at any auto parts store. The controllers are special, usually orderable, items which usually only add useless whiz bang features.

The sensor I'm using is just a thermally actuated contactor, only making contact and allowing continuity at or above it's rated temp (within it's tolerance of course). It's similar to the cooling system thermostats in that thermal expansion coases motion. The motion either makes or breaks electrical contact. When there is contact current may flow, when it breaks current can't flow. In other words it acts like a relay driven by temperature. With an ohm meter its either open circuit or short circuit, never anywhere in between.

ya but in the picture it just looks like a temp gauge sensor and there must be a change in resistance as it gets warmer

Use the type of sensor I've described. The circuit won't work with a continuously variable temp sensor like an RTD. You need the contacting temp sensors which are readily availabale at all auto part retailers.

Crazy Your right, seems to me the vehicle in the DIY has a temp sensor in the radiator already. 240? what's that? a 240Z maybe. SO you'll have to wire it in to the one on the manifold or buy the temp sensor you stick in the fins.

Or use the adapter I tried linking in post 3. Along with a sensor like this http://www.jegs.com/i/JEGS-Performan...rentProductId= which acts a a thermal threshold switch.

Yep, sorry , I missed that.

No problemo man. Just making sure it's nice and clear since this illustrates the important, in my opinion at least, point that spending money for the controllers isn't required.

That's pretty cool, so this system will turn it on at full power right? My amp and hella lights worry me with getting an electric fan

What size alternator ya got?

You could also install a capacitor in-line with the power feed to the fan, so it wouldn't suddenly be this HUGE draw..... Not sure what size would be good to use though.