the only thing that is left to replace would be the radiator?my truck is a 1994 f150 and it is not overheating!i get lukewarm heat only on the highway,everywhere else it is cold air!!this new england weather is killing me any help would be great.thanks ken

 

Where does the temperature gauge sit?

 

Is there a gate valve on one of the heater hoses? It could be not opening when you move the controls on your dash to the heat. It could be vacume or a cable.

 

Did you buy an el-cheapo thermostat from Boydowecheatemandhow Auto Parts? There was a discussion a while back regarding the springs being weak in low priced thermos and it allows them to open too soon. Concensus seemed to be that spending 10-15$ from a retailer such as NAPA was worth it.

 

my guage sits at the 10 oclock position.i put two different ones in ,first a 195 and now i have a 165 degree thermostat.they were bought at pep boys

 

There is a blend door that controls how much hot air from the heater core blows into the truck. I suspect that the blend door is stuck in the cool position.

 

where is the blend door located?i didnt see any such thing when putting in the new heater core?

 

The heater air plenum chamber is located in the passenger compartment. It contains the:

l Mix door (for directing a mixture or total air to the floor and/or defroster/demister outlets)

l Temperature blend door

l Panel/Defrost door

l Cam/crank which operate the temperature door

l Heater core (18476)

l Vacuum control motors which operate the mix and panel/defrost doors.

The windshield defroster hose nozzle is formed into the instrument panel with outlets to the windshield and hoses which attach to an adapter located in the center of the instrument panel for demisting.

The air conditioner control (19980) is installed in an opening in the instrument panel. It contains three *****. One **** operates the four-position heater blower motor switch (18578) and one selects the function under which the system will perform (OFF, MAX A/C, NORM A/C, VENT, FLOOR, MIX or DEFROST) by controlling the vacuum control motor. The third **** regulates temperature by means of a heater temperature cable (18518) which controls the position of the temperature blend air door.

 

 

I'm have the same problem. Replaced water pump, Thermasat, new heater core and flushed system. All the control values are moving but still no heat. The only thing I didn't replace is the radiator. Trucks not overheating just no heat in the cab

 

Are the hoses hot?
if so it's not in rthe engine bay.

How's the blend air door?
If it's stuck shut all you get is unheated air.