I have a 98 Civic LX 4 dr. I haave had this problem for a while. I get HOT air blowing from my vents into the passenger compartment all the time. My temperature is set to cold and the fan is turned off. The heat and the air seem to increase as I accelerate with time. buit it takes no more than 3-4 minutes for it to start blowing hot air once I am driving. And i slip my fingers into the vents, and it is so hot in there, it burns my fingerrs if i leave them for more than a few seconds.

Is there a firewall that prevents the engine heat to be sucked into my passenger compartment vents?

Any ideas on how to troubleshoot will be very appreciated.

Thanks

 

It sounds like the heater is stuck on. That could be a damaged part of the climate control system in the dash, a stuck heater valve, or similar. The heater core is in the cabin, so if it is stuck on "hot" you have to deal with it until it is fixed.

By the way, the 3-4 minutes is the time it takes for the engine coolant to warm up and bring hot coolant to the heater core.

 

Not familiar with these cars, but I would also say, it definately sounds like a stuck/broke heater door.

 

WHen I said temperature is set to cold, I meant the temperature control lever is set to low. Even when its all the way towards the blue end, I still get HOT air coming in. The only thing that affects how hard it blows is how fast i am driving and how long i have been driving. usually like I said 3-4 mins is good enough to get HOT air coming out of the vents.

And yes the fan turns on. but I dont turn it on cuz I dont want it blowing even harder on my face.

I am thinking for some reason the air is sucked into the vents. Its not just that it feels hot there, i have air comimg thru the vents.- HOt air.

I thought maybe something is up with the heater/ac thing so I pulled the fuse for the heater/ac in my dashboard fuse box . NO change. Still get hot air blowing.

What I am puzzled is where is this air coming from? I can say the heat is coming from the engine. How about the air?

Thanks for yr replies

 

:doh: Did you actually read my post? Pulling fuses will NOT fix that. The heater is a purely mechanical system, hot coolant from the engine flows into a heat exchanger under the dash. The air coming though the vent system has to flow through the heater core, so if it is stuck on, it will blow hot air regardless of what temperature the slider is set at.

The engine takes about 3-4 minutes of driving to warm the coolant, that is why it will blow cold for a few minutes. There is no hot coolant in the heater core until the car warms up.

You must be thinking there is a little electrical heater in there... there isn't. The "hot" comes from engine coolant.

 

Oh I get it now. Thanks for pointing that out. Now I will have to open up my dashboard and look for the heater is stuck on. I hope it is nothing more than a missing clip on the heater control line. How else can it be stuck on Max heat all the time? Can you guys see any other possible causes ?