Recently bought an 02 4Runner SR5...went to turn defrost on the other day and no warm air. All cables in place, no change when I unhook valve on firewall and manually move valve, AC works, air changer works....nothing "moves" under dash when changing temp settings?? No biggie now but once it get's cold....HELP!!!!

 

do you get heat from under the front seats. It may be a clogged heater core. or the doors are not moving to redirect the heated air to the vents. Are both of the heater core pipes hot of just the inlet?

 

Luke (very luke) warm on warmest setting....almost non existing. Checking core pipes tonight...know all hoses were warmed up the other day. Notice no movement under dash when I adjust/turn temp knob....

 

From what I see in the FSM there is no heater core valve and fluid should flow continuosly thru the core. So why isn't the coolant passing thru the heater freely? Bad water pump or clogged heater cores come to mind. Have you flushed the coolant lately?

FSM rare heater

FSM front core

 

does the rear heater work? if it does then then the problem is limited to the front heater box.

does the controls for the air flow direction work? I mean the air flow for the legs and for the windshield. if not, then the doors to the heater box aren't moving. first check would be to remove the center panel sub-assembly and check if the plugs to the ac controller are properly connected. if yes, try turning on the ac and try the directional controls. if you don't hear/see any movement, then most probably you have defective solenoid motors that control the gates or maybe just got disconnected somehow. these are a bit expensive so you might like to consider second-hand ones from part-outs

 

An air pocket in the heater core can cause this. Bleed the cooling system for that.
Under the passenger side of the dash, you should see the blend door lever. It should move when switching from hot to cold. There is also a mode door that moves when switching from vent to heat to defrost. Is the blend door moving? Is it cable or actuator controlled?

 

Ok had time to dig into this issue. Found that the part numbered "063700-8380" or air mix control servovalve was disconnected. Took it out and manually moved the metal lever connected to the cable which runs to the water valve under the hood. Presto, heat...now, can't seem to locate the part??? It appears someone had disconnected the power to this and put it back without the white plastic arm connected to the above metal lever. Plugged the motor into wiring harness and it maybe moves an eighth of an inch. Ebay has tons of these motors, just not this particular model...grrrrr....

 

on the SR5, there are two servos controlling the dampers. one is on the side, the other is located underside. The number you provided above is not the part number.

after identifying the location, you can check some of the part-outs as there may be a working servo that you can use instead of buying a brand new one

 

I assume that this servo is supposed to move more than an eighth of an inch....