Ford: F150 Heater, temperture, ford dealer

Question
Hi!
I have an 1999 F150 Truck with 91,000 miles.  The problem is with the heater.  Originally, the problem was that the heat would not turn off completely when I turned the temperature dial to the collest setting. There would be warm(Not HOT) air blowing from the vents.  Now the problem seems that I can't always get HOT air to blow out when the temperture dial is set to the hottest setting. Lately, after the engine has fully warmed up (as indicated by the temperture gauge) and I have only cool air comming out with the temperture dial setting on the hottest setting,  If I twist the temperture dial back in fourth between the hottest and coolest setting eventually I can get some heat to come out.  It may take 20-30 minutes of playing with the temperture dial before I get heat to come out but not always. Sometimes I cant get any heat out.  It seems to hold the last temperature setting.  If the cold air was on last you can't get the heat on.  If I had the heat on and I dont touch the temperature dial it seems to stay on.

I took it to the Ford dealer to have it cheacked out.   In order to duplicate the experiance to the dealer I left the temperture dial on the hottest setting with no warm air after the engine warmed up and drove to the dealer.  The heat just came on as I pulled into the parking lot.  This was the first time I didn't play with the temperture dial at all and the heat came on.  While at the dealer, they replaced the thermostat which did not fix the problem. I've since taken it back to the dealer which initially it had the same problem until they pulled it into the garage and the heat just came on.  The dealer seems reluctant to try to fix anything at this point beacuse they already charged me $130.00 to fix the wrong thing.

Now I'm not sure weather working the temperture dial back and fouth frees something up until the heat comes on or its a time related issue that it just takes 30-40 minutes for something to free up.  Do you have any suggestions on thing to tell the dealer to look at???   Thank you in advance.

Answer
CONDITIONS DETAILS/RESULTS/ACTIONS
B1 CHECK FOR PROPER ENGINE COOLANT LEVEL

 

Check the engine coolant level when hot and cold.


Is the engine coolant at the proper level (hot/cold) as indicated on the engine coolant recovery reservoir?
Yes
GO to B2.

No
GO to B3.
B2 CHECK FOR HOT WATER TO THE HEATER CORE INLET HOSE
WARNING: The heater core inlet hose will become too hot to handle and may cause serious burns if the system is working correctly.
NOTE: Be sure that the inlet hose flow restrictor is in place and is undamaged.

 
Allow the engine to reach normal operating temperature.

Feel the heater core inlet hose.


Is the heater core inlet hose too hot to handle?
Yes
GO to B4.

No
GO to Section 303-03A.
B3 CHECK THE ENGINE COOLING SYSTEM INCLUDING RADIATOR CAP FOR LEAKS

Fill the engine cooling system to specified level.
Pressure check the engine cooling system. For additional information, refer to Section 303-03A. It is not necessary to check the components separately at this time.


Does the engine cooling system, including the radiator cap, hold pressure?
Yes
GO to B4.

No
PRESSURE TEST the heater core.
B4 CHECK THE HEATER CORE OUTLET HOSE FOR HOT WATER

Feel the heater core outlet hose.


Is the heater core outlet hose cool or cold?
Yes
TEST the heater core for a plugged or partially plugged condition.

No
Go To Pinpoint Test D.
 do this and let me know what pinpoint test we need to do next.