I one day found my 1998 F-150 Heater and a/c blower only worked on high. After checking with my dealer they told me this was a costly repair, around $200. I consulted with a local auto parts store, and found the problem could be repaired for only around $18. If you have this problem you most likely need Ford part #4L3Z-19A706-AA Resistor. You can find this part on the passenger side under the dash, just above where the passenger's feet rest. With a plug in connector, and held in place by two screws it takes only 15 minutes or less to replace. Hopes this corrects the problem for you, and saves about $180.

 

I had the same problem on my 1999 f-150. The resistor took care of it. I got it for about $15 from a Ford dealer. Thanks.

 

i have the same problem but i dont even have the 15 dollars to fix the problem