It takes awhile for my 95 Dakota with 77,000 miles to warm up. I've replaced the Thermo,water pump, belts and hoses. Heater core does not leak. Also it only blows luke warm air on low fan speed. If I increase the fan speed it will only blow cold air.
Need help

 

What's "awhile"?

 

I would have the cooling system flushed, maybe pull the radiator and have it rodded out. Then go through it again, coolant mix proper? new thermo, etc. Also, have you replaced the temp. sensor?