My heater only warms when driving over 70mph . And I also hear a blower fan that seems to constantly run .. Any suggestions ????

 

https://m.youtube.com/watch?v=WPnJnkZ58Hc

Have you checked the blower motor resistor? Does the fan only run on one speed and make a lot of noise? Does it seem to blow out of only the dash/defroster or a/c vents?

I had a similar situation in a '97 Explorer.
It was 23 miles to work in a Michigan winter. Got heat about the time I pulled into the driveway on either end. Replaced the resistor and had heat within a mile of startup.

 

Low coolant level? Air in system? Bad thermostat? all common problems.

 

Low Antifreeze was was causing the problem . Got about a foot of snow on the ground . But as soon as we get a warm spot , I'm flushing the whole system . Thanks for the input guys ..