Heater not working properly?

The only other thing I can think of is to check the mode or temperature actuator under the dash.

They are directional doors, I'd have to look.

Hi there,

The heater tap may not be opening at all, disconnect the two hoses and using a garden hose on LOW pressure try and flush core with tap open, if no flow, try and access the heater tap and check operation, also check that the heater controller is working.

Mark (mhpautos)

Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or do a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also check the thermostat, and the temperature blend door, thats under the dash, in the heater plenum.

I think you installed the wrong thermostat. The temperature rating is marked right on the thermostat.I'm thinking it should be around 190. Go to the parts store and have them look it up.

You'll have to check to see if the actuators are getting power ornot. They are under the dash. I'll send a pic of a generic heater to give you an idea where to look. Theblower may not be working on high due to the high blower relay notworking. Here are the thingsto look at.

First look for a bleeder screw on the thermostat housing. The thermostat wont open if there's air under it. If there's no bleeder screw, look for a sensor on or near it that can be removed while you fill the coolant.

If you get the air out but coolant still doesn't circulate, bleed it again while the engine is running. If you continue to get air, suspect a leaking cylinder head gasket. The combustion gases will pool under the thermostat preventing it from opening. Your mechanic can perform a chemical test at the radiator or reservoir to verify a leaking head gasket.

When it doesn't operate on high, check the switch and the resistor this way:
BLOWER MOTOR OPERATES AT LOW &/OR MEDIUM SPEED ONLY

Turn ignition on. Set blower switch to high speed position. Connect test light between Orange wire at blower switch connector and ground. If test light glows, go to next step. If test light does not glow, replace blower switch.

Connect test light between orange wire at blower resistor connector and ground. If test light glows, replace blower resistor. If test light does not glow, repair open Orange wire between blower resistor and blower switch.

Normal thermostat for this vehicle is 195 then when cooling system Is full run at 2500 rpm's until truck heats up let engine cool and recheck coolant level.