so you cant install a 97 and up motor in a 96 and down jeep.Extend the rear temp sender wire to newer style thermostat cts ground and it work the gauge....in laymens terms.

 

Looking at a 0630 head I have around (early OBD-II, 1996-1999 use,) it seems that the boss is still in place - but that it wasn't drilled & tapped.

Options:
- Locate boss, punch to locate drill, D&T 1/8" NPT to accept switch.
- Get a "hose bung." Typically, this is an aluminum part that has hose barbs on both ends, and a short section in the middle with a threaded port or two (typically 3/8" NPT, which fits most common parts.)
- Drill a hole in a radiator tank, and solder a bung there.
- Find a "non-invasive fan control kit," instead of using a "wet" sensor, it runs a sense rod through the radiator fins against a core tube to sense the temperature. Check with Flex-A-Lite or other companies that supply for the RV/recreational towing industry for these, you can often find them in local stores.

Probably a couple I'm not thinking of - those are just the first ones.

 

I have seen all these options , you seem to be the electrical guru here in your opinion the only way to see if other way would work is just try it .

 

No - if you want to use the CTS in the back of the head to trigger the fan, "just try it" will NOT work.

You must find a SWITCH that is going to work at the temperature you want (for that location, I'd probably look for one that triggers ON at 205*F and OFF at 195*F,) because the OEM sensor found in that hole is a sensor with a variable resistance, NOT a switch. You MUST use a switch to drive a relay - and I don't know if you can find one threaded 1/8" NPT, which is why I threw out the other options.

 

Not worried about fan am wondering about gauge on dash .