I have a 2001 ram 1500 4x4 with 73k and it has no heat the a.c. works fine but no heat

So then I assume your blower is functioning correctly?

Does the vehicle overheat? Do you need to add coolant every now and then?

Assuming all of the above is correct, do all of the functions on your heater control panel work?

Does is it feel hot under the passenger side of the dash?

Reverse flush the heater core and possibly the whole cooling system. Corrosion and/or phosphate scale may be blocking passages. Afterwards, refill with a 50/50 mixture of Zerex G-05 (HOAT) antifreeze and distilled water.

my wife has a 2001 ram 1500 4x4 with 115k miles. We started having problems about a year ago with the heater. A year earlier we had problems with a/c so we had dealer relplace evaporator. a/c works fine, but now heater is acting up again. It only puts out air at 100 F +/-. We took it to our mechanic friend, he has reported that timing chain cover is leaking anti-freeze and that timing chain is very loose. He thinks that by replacing a few seals/gaskets and tightening chain, we might be able to get heater working like normal again. We'll see. Hopefully this works. He said that upper hoses were hot and lower hoses were cold, no circulation through radiator.