I just notice that my heater(99 C280 Sport) seems to be on the fritz. I can get HOT heat if I use the defroster, but it will not throw heat out the vents at any of the settings. I've checked for leaks and there are none . Core seems to be doing it's job, but there just isn't heat comming from the vents. I'm thinking a door flap must be either stuck or just not closing properly. Can someone give me ideas as to what to look for? Are there relays for this or am I looking for air leaks?? There looks like a diverter valve on the right side cowl area under the hood that has hoses going into it, that has an electrical connector on it. Is that maybe the culprit?? Thanks for ANY information.

 

Maybe the BOTH valves in the duo valve are stuck closed and not letting in any water? I would tap the duo valve cylinders firmly but not too harshly as someone changes the heat setting for you, back and forth from high heat to medium heat. See if you can loosen those up.

 

Ya I gave it a nudge yesterday and it seem that this AM they were working. Had heat and was very comfortable driving. Guess I'll look around and replace this valve when I get one. Thanks again.

 

Yeah, it is common for these to start sticking if they have not been used all summer. Sometimes they work fine after being unstuck. Others, they need to be cleaned or replaced. Replacement is pretty easy according to posts on the net but the part is pricey. Stealerships love to replace these and don't repair them. Big $$. You can try to repair them but people often destroy them while trying to fix them.