Howdy.

I have a 1994 Celcia ST as a backup car, and a 1995 Celcia GT as a daily driver.

My 1994, the radiator has been replaced, and the fan motor. But the fans still won't spin. I can drive it, but not idle for long, or the coolant will boil and spit out.

I actually drove it all the way from Maine to southeast Georgia without issue, as long as I don't idle for long. Funny huh ? Over 1,200 miles in a few days without a working radiator fan. The airflow keeps it cool.

Today I took the known working relay from my 1995 GT and put it in my 1994 ST, and the fans still don't work. I let it idle until the coolant started to spit out. That took around 15 minutes I think.

So, fan motor, relay ... What should I check next ?

Thanks !
Craig

Maybe this ? https://www.ebay.com/itm/New-Coolant-Temper...54AAOSwMjVfhsjc

OK, I will order a water temperature sensor, as it is only $10.

Oh I think it's this one instead, still not bad for $14 off eBay

I hope it will fix the problem ...

Fans can be tricky to diagnose... First, test the fans themselves: disconnect the radiator fan switch plug at the bottom of the radiator, and the fans should turn on and stay on regardless of the radiator temp. (in other words, don't do what you did risking overheating the radiator).
If the fans don't turn on, start chasing relays. There's more than one radiator related relay. Check fuses, too.
If the fans do turn on, check the radiator switch itself. It should be closed (as in, no resistance) when cold, and open when hot. It if's open when cold, the switch is bad.
Give that a try, let us know what you find.

Thanks Slavie,I'll see what I can find.