any idea?

[3xnet]

Does anyone have an idea why my heater stoped blowing hot air? it blows cold air when ever i turn the heater on?


what could be the issue?

[Brett San Diego]

The duovalve regulates the amount of hot coolant that flows through the heater core. If your valve has failed and no longer operates, no hot coolant will ever circulate to the heater core.

See pcmaher's excellent work rebuilding his rear climate control valve to see what the beast looks like in general.

http://v12uberalles.com/Rear_AC_System.htm

The main climate control duovalve is similar. It's mounted just behind the driver's side headlamp in US cars.

Brett

[3xnet]

Brett, thank you for caring to reply. I really appreciate it. they told me today that i need heat control unit. it is located just behind driver side head lamp. i guess its the same thing you refered to on your post.

thanks

[ulflei]

I think a heat controll unit is not the same as a duo valve,at least it sounds more expensive.

[Brett San Diego]

here it is from an aftermarket supplier. It could be cheaper from another source.

http://www.autohausaz.com/search/productx.aspx?sid=4blkip45nortuoz0xkdvn2q4&makeid= 800016@MERCEDES&modelid=1195848@S600%20140.0XX&yea r=1997&cid=24@AC%20%26%20Heat%20-%20Climate%20Control&gid=6860@AC%20%26%20Heater%20 Control%20Valve

Looks like a piece of cake to swap it out. You might also try the climate control diagnostics as outlined in the "knowledge base" thread. If the duovalve has an open circuit, it should be indicated.

Brett