I just recently had my heater core replaced in a shop and when I got it back it still has no heat. They tell me it's the blend door so I pop the glove box off to make sure the servo is working correctly. It is. I searched the forums and did the heater control valve tests and it is working fine.

Next I made sure the coolant is topped off and run the car a bit with radiator cap off thinking maybe it's vapor locked. Still no luck but when I put my cap back on I notice I have zero pressure on my upper radiator hose. I also notice that under high acceleration the core seems to gurgle a bit. I popped the hose on the side of the heater control valve (at normal temp) and I get only a moderate amount of coolant out of it which trickles to a stop after the initial bit. This is with the car running at normal temp.

I am going to replace the cap and thermostat this afternoon and I just want to confirm I am on the right track and not missing something. The car does not overheat in the least but I am thinking maybe this is preventing pressure and not feeding the heater core? Is there some kind of safety cut that when I pull the hose off the heater control valve that would stop the flow out of the block? Could it be the water pump? I would think if it's the thermostat or pump that i would have overheating issues which I have none.

 

Changed the thermostat and the cap. The hoses now have pressure but I still dont have heat.

The inlet and outlet are both hot but no hot air inside.

The climate control gave me an error code 41
(The source of code 41 can be from either the Air Mix Damper Position Sensor circuit or the Air Mix Control Servomotor circuit. It may be necessary to complete both inspection procedures below to find the source of the trouble code.)

Anyone know where either of these are located? I have about 1/2 of the dash removed and all the dampner doors on the outside (that I can see) are opening and closing except for the floor/console blend door which is slightly ajar. I am thinking it must be the actual blend door but where is it? Any help would be appreciated!!!!

 

I have searched every post on the forum with the word heat in it. All I have come up with is one post on flushing the core with a garden hose which I will try tonight. Can anynone point me to where the air mix dampner is? Is it inside the heater case or on the outside? Alldata's pic is to small for me to pinpoint the location so please, bump for some help!

Recap
Coolant is completely full. Ran the car to n.o.t. with the cap off refilling as needed. Drove it and then topped it off again.
Control valve is in the up position and changes with the temp ****.
The only door that I can tell isn't working is the one just to the right of the center console. Pusing it open and closed with my hand makes no difference.
Both metal lines sticking through the firewall are hot.

Anyone??

 

What Test did you do on The HCV? You have to take of the connector and measure resistance and also measure the Voltage on the connector disconected. I have gone through all of this to on my 93 SC. What i found was that the Climate control unit was sending the signal to the HCV at 80deg which was to late. I pulled off the little arm that on the valve and disconnected the plug. Now I have heat all the time aqnd in the summer I will move the valve back to shut off the heat. Its hard to explain. I will try to find the tread that I found this on.

 

The way I understood the hcv to work was either open or closed. It opens and closes with the **** inside the car and also will open and close with the vacuume hoses. I also have checked both the inlet and outlet piping coming out of the firewall and both are extremely hot to the touch. If you can find this link about checking the wires I will gladly try it but I believe the valve to be working.

 

Last night I completely emptied my cooling system and removed the hoses from the hcv as well as removing the thermostat again. I used a sprayer on a garden hose to flush the engine block, radiator, and heater core. I tried various methods to make sure nothing was clogged in my system to include holding the hcv open and spraying through it. I didn't find a single clogged thing in the system.

What am I missing here? I have coolant flow all through the system but no heat in the car. Any ideas??? Surely there must be a blend door inside the car?

 

Well to any of those that read these few posts with heater woes, here was my fix. There is a servo on the bottom of the heater box located right next to the firewall/center console on the passenger side. It operates two doors which are blend doors. It seems my heater dripped into this box and burnt the little 2"x4" servo that operates them. FYI Gazi is the man and is going to get me one. The things you need to remove is the under panels on the passenger side, pull the carpet back and remove the plastic tray covering the ecm. From there you should have access to it but I had to break one of the three ears that held it in place. It is almost impossible to get the screw out since it has less then 1/2" of room to come out. The wires are also hardwired into the box and go somewhere up behind the heater box itself. I have no idea where they plug into or join the harness at but two screws and splicing them in will make it work. If you want to do it "correctly" I see no way but to remove the heater box itself which means pulling the whole dash out. Good luck with that!