I recently purchased 99 4runner. It had heat issues before I got it. Previous owner had the system flushed. Seemed ok but, it didn't last. Here are the symptoms. No heat out of console, Some heat out of center vents, No heat out of defrost, no heat out of window dash vents. This is all with the fan on high. Plenty of air coming out. Then the other night I took it to get it oil sprayed. Did all these things on the way there. However, after it sat during the oil spray process when I got back in it, everything was blowing HOT air except console. Now, the blower was not on high. It was about medium. When I turned it up on high started losing temp. My Toyota tech friends said it must be the doors in the heater box. I don't think its the the thermostat cause the truck heats up quick. Don't think its the heater core cause no leaks or smells etc. I removed the dash last night and I don't see anything wrong with the doors that divert the heat. However, I'm not sure where all of them are. Is there one inside the heater box where the heater core is? Thanks in advance for the help.

 

Rodent nest ?

How did the AC work??

Heat works best with the controls set to outside air

 

No rodents. I guess the A/C worked fine claims the previous owner. The outside air thing didnt make a difference.

 

Sounds like the Heater valve is not opening like it should .(on the firewall)

You might be getting some flow just enough to be luke warm

 

Ok, I have it finally fixed. The heater core was apparently plugged. I backflushed it 4 or 5 times. I also put C.L.R. in it to help break up the deposits. I even let the CLR sit in there for 24 hours. I used air to do the flushing. I took the fitting off a tool and just blew full air from the compressor. Caught all of it in a clear milk jug so I could see what I got out of it. I also rinsed several times with distilled water and blew it out to make sure I got all the CLR out. Lastly I filled the heater core with fresh asian specific antifreeze to help reduce the whole air bubble issue. Heat is great now. Hope this helps someone else with the same problems in the future.