2003 Lincoln Towncar - when should the radiator fan switch on?

Yes...the engine has to be brought to the operating temperature of 195...until it gets to this point fans will not come on, as the sole purpose of your thermostat is to block the coolant flow until operating temperature is reached~....now it it's starting to overheat, we must look 'pon the reasons~

the engine coolant temperature switch could be buggered up~ http://www.partsgeek.com/gbproducts/MC/5670-07088180.html? utm_source=google&utm_medium=ff&utm_content=MC&utm_campaign= PartsGeek+Google+Base&utm_term=1999- 2003+Lincoln+Town+Car+Engine+Coolant+Temperature+Switch+Standar d+Motor+Products+99- 03+Lincoln+Engine+Coolant+Temperature+Switch+2002+2001&gclid=C NnNxdzThLkCFYtDMgodbAIAUg

Most cooling fans turn on around 210 to 212 degrees, that is why it is imperative that you maintain your cooling system properly with a proper mix of antifreeze and water and a good pressure cap. The cooling fan should also turn on with the A/C compressor, some systems are tied in with a high pressure switch that turn on the fans when it reaches a predetermined pressure setting. So to answer your question yes it is normal as long as your cooling fan turns on around those settings.

If it isn't overheating, don't worry about it. If it isn't working properly you will know soon enough. The LTC cooling system works great unless something is broken, then you will know very quickly.

01 town car- can I use the ac high pressure switch to trigger (with a 30/40 amp relay) the fan on high. Doing it this way, will it turn low speed off automatically?

No the high pressure is a cutout switch. The integrated fan controller is suppose to handle all fan operations, is your bad?

I have no doubt it is good. Here in Phoenix the temps get high and rarely does my high fan speed kick on. (Good cooling) but I was hoping to by-pass it and activate it somehow. You got any advice on this?

Without fouling up the existing system no. You could always install a push fan out in front of the vehicle that you could wire into the compressor wiring with a relay so when the A/C compressor turn on the aftermarket fan also turns on, just make sure you get a big enough fan or two smaller fans to fit the clearances you have out in front exchanger unit. HTH

Doing it the way you suggested, wouldn't that interfere with the putter putter enough In? Sorry spellcheck problem

The puller not get enough air in

No cause you would be using a pusher fan, when it is shut off it will freewheel so the air flow won't be obstructed very much.