Have had a PRC radiator setup with dual Spal fans installed and working properly on my 57 nine passenger wagon for many years now. The programmable fan controller allows you to set the low temp-Single Fan ON and the high temp-Both fans ON at the temps you want for your engine.
Mine has been working flawlessly for about 5 years now.
All of a sudden, things changed a week or two ago.
I noticed when I start the wagon, both fans are always ON....and stay ON...regardless of what the water temp is. Also, turning on the AC doesn't affect this anonmaly....they fans are always ON both of them, full speed.
So I recently went back thru the programming procedure on the controller, setting the LOW and High temps, and cannot get it to work as before. No matter the "spread" in the Low and High temp range, the controller now doesn't work correctly, and just "blinks 3 lights all the time" (indicating the temp spreads are not wide enough). I've tried several times at reprogramming the controller, each time with wider temp spreads, and it will not work.
So I'm going for the lesser expensive part in this equation...the temp sending unit in the drivers head. This is where I've had the sender all along, and it's a 2 wire late model style, that drives the Spal controller and also the stock dash gauge. It's about a $35 part from Napa, and I'll know later today if that worked.
if not, then the controller is probably shot. (If that's the case, then this will be the 3rd Spal controller in the 10 years since I've owned this wagon. The first one died after 2 years due to water getting inside it. This one the second one, is mounted in a dry location in the engine compartment)
On top of all of this, I noticed the PRC aluminum radiator has sprung a leak. PRC welds their radiators to the cross bar, so pulling that to get it fixed will be a bigger job than it needs to be. Aargh...