A 94 Corvette with the LT1 (VIN P) engine has no sensor or switch which directly controls the cooling fans.
Both fans are controlled by the ECM though two cooling fan relays. The ECM relies on the ECT sensor and the HVAC pressure sensor along with its programming to set fan-on strategy. The engine coolant temperature sensor is in the water pump and the HVAC pressure sensor is in the A/C evaporator line.
Eckler's tech support are morons if they are telling you a 94 LT1 has a "fan sensor" or a fan switch" installed in one of the heads. There are no sensors in either head of a 92-96 LT1. In fact their sales staff are morons for selling you such a piece of crap of an aftermarket product.
What Eckler's "kit" does is modify the cooling system for simple coolant temperature control of the fans. Installation of that kit requires you disable the ECM control of the fans, install an additional temperature switch in the cooling system, then bastardize your cooling fan wiring harness.
Worse yet, installation of this kit disables the ability of the ECM to control the cooling fans when A/C is running. It, also, disables independent control of the two fans and has both fans running whenever the switch closes. Finally, it disables the ECM's ability to request fan-on as a protective measure when certain ECM fault codes are set.
If you insist on installing this kit, you have to read the poorly-written instructions carefully to understand that to make it work with an LT1, you must install the kit's coolant switch into one of the heads, after you, first, remove one of the plugs GM put in the heads using a tool you have to make. Then you have to rewire the fan relays such that this switch, rather than the ECM, controls the two fan relays.
I suggest you send the kit back to Eckler's and get ask for a refund.
Then, take advice "ecss" offers and purchase TunerCat's LT1 kit. It will allow you to reprogram the ECM's fan-on strategy but preserve the ability of the HVAC to request the cooling fans, preserve independent operation of the two fans and preserve the ability of the ECM to command the fans on when certain DTCs set.
Then, what I'd do is: verify the thermostat is a 180°F unit. If it's not, purchase a Stant 45218 from CAC sponsor Rockauto.com and install it. Finally, using TunerCat, program the following fan-on/off numbers into the cal. as a starting point:
Fan 1 on at 200 and off at 192
Fan 2 on at 212 and off at 200
Also, with C4s, there are a couple of other key cooling service procedures you should perform.
1) Remove the top of the cooling stack and inspect the upper part of the HVAC condenser for debris restricting airflow though the HVAC and the radiator. Then inspect space between the HVAC condenser and the radiator for debris. Remove any debris blocking airflow.
2) Inspect and, if necessary test, your coolant pressure cap. If it's bad, replace it with one from CAC sponsor, Rockauto.com
3) To properly cool a C4 MUST have its stock, front air dam. Make sure the front air dam is in place and in good condition. If it's not, you can get a replacement from CAC sponsor, Zip Products.
4) Change your coolant if it hasn't been done in the last three years or 36,000 miles.
5) Inspect all your coolant hoses and replace as necessary.
Good luck, my fellow Corvetter!