I have a 97 4Runner with 158xxx miles it's been a long cold Wisconsin winter and after installing 2 new t-stats a new radiator new water pump and new heater core the heat still won't work while it's turned on idling there is some heat when I turn it on low but when I start driving and or turn it up to high it's just cold air I checked the valve under the hood and it opens and closes also when I switch from hot to cold
Any one have any suggestions

 

Do the foot, dash, and defrost positions seem to change appropriately when selected??

How bout the outside air and recirculate functions?

There may well be trouble with the selection and blend doors inside the air plenum.

 

Do you lose coolant, or are you low on coolant?

I had the loss of heat as an early precursor to a failed headgasket as the signal that I was low on coolant and not enough to circulate thru the heater core circuit.

 

Yes all the functions seem to work fine and I have AC as for the coolant the level is good

 

Just where do you live that you need heat this time of year??

Sometimes it looks like a broken heater valve works it moves but the internal parts don`t move.

Checking that cables are still attached can be a pain.

AC not shutting off

 

Ac not shutting off shouldnt matter.... It comes on when u use the defroster and full heat anyway....

I would thunk its something inside the plenum... Doors might be sticky

 

Alright I'll check it out but the AC does shut off and on
I'm just trying to get this worked out before fall comes around

 

You should hear and feel the doors open and adjust when you move the slider for the direction and well as the fresh vs. recirc. If you can't it maybe a cable issue.

 

Well.. New to the board but solved this... The issue is the level of "Flush" that has been done is not enough to get the rust out of the heater core.

Short notes that eric the car guy.... and I did..
1) Mark the in and out lines where they go into the heater core on the firewall.
2) Detach both
3) Attach Vinyl tube to both in and out of the heater core. "Chris fix... i liked his clear vinyl tube approach."
4) Use an Water nozzel on a hose and spray water (not super strong) in the reverse direction than what it was designed to flow - Go in the exit and out the entrance.
5) once it starts to clear out (because you are using clear line to observe...) Use an air hose to blow out the water from the heater core.
6) then pour CLR - at the approved mix rates listed on the bottle - thats right the stuff for cleaning your shower - CLR - Calcium Lime Rust remover - in the out door holding the hose up till you observe the CLR has filled the heater core.. How do you know this... you have both the hoses higher than the hose opening of course!
7) wait 30 min... then flush thoroughly with water.
8) While you have the hoses off... is there any red residue in the bottom of your coolant lines going to the heater core? There sure were in mine....
9) reassemble.... and now you have a working heater!! Just like mine.
10) Remember step 8? - If you have a bit of residue in the line... they you probably have a situation like my latest purchase 200K miles and I suspect never flushed the radiator / coolant system.. so schedule your next mission to flush and flush and flush some more to clean the radiator and coolant system using the Prestone flush stuff and proper washing out of the radiator.

Hope it helps.

Eric's shop of wizardry

Chris Fix doing a similar approach

A bit more labor intensive approach..