Heating issue

[geopete]

Hi all, new to this forum. I bought my son a 2004 Civic 1.7l.

As winter is settling in here in Canada I figure heat will be needed.

So far I have replaced the thermostat, heater control valve and bled any air bubbles in the system. And still cannot get any good heat. Temp on sensor is getting just below half and there's no heat while driving.

Is there another mixing valve/air mixing box I'm missing?

Thanks in advance!

 

[Mr.Baker]

Going into firewall are two 2 hoses, leading to the heater core.
With your car sitting and idling until it gets up to operating temp, turn your heater on and check the hoses by placing your hands on both, see if they are similarly hot.
If the one on the right is warmer than the one on the left. your heater core is plugged, you'll have to flush it.

 

[geopete]

Going into firewall are two 2 hoses, leading to the heater core.
With your car sitting and idling until it gets up to operating temp, turn your heater on and check the hoses by placing your hands on both, see if they are similarly hot.
If the one on the right is warmer than the one on the left. your heater core is plugged, you'll have to flush it.

Ya already ruled the heater core out. Both lines get to equal temp.

I'm wondering if there is an air mixing box under the dash that might be allowing cold air in and mixing with the heated air.

 

[geopete]

If you manually open the heater valve, does the air get hot? If not, bleed the cooling system.

Yup it's open all the way. I'll try bleeding it more. Thought an hour at idle plus after driving would've been enough.

 

[geopete]

Does the cabin blower move air through the vents?

Nope both get to full temp. As hot as the upper rad hose gets.

 

[daperez13]

Did you purchase the car with this issue? If so, did the previous owner give you his opinion as to what the issue might be?

When you bled the system, did you have the front of the vehicle lifted up, temp dial on it's hottest position and the fan on it's highest setting?

Have you checked the temperature control switch to validate it's functioning properly.

Did the car have any prior over-heating issues?

 

[geopete]

Did you purchase the car with this issue? If so, did the previous owner give you his opinion as to what the issue might be?

When you bled the system, did you have the front of the vehicle lifted up, temp dial on it's hottest position and the fan on it's highest setting?

Have you checked the temperature control switch to validate it's functioning properly.

Did the car have any prior over-heating issues?

Bought the car at an auction, it had this issue last winter. I was able to resolve it by bleeding the system after installing a thermostat. Turned the heat mixing valve off for the summer and now I'm having same issue.

I haven't tried bleeding it with the front end raised yet, I'll try that this weekend. Switch works fine.

Has never over heated since I bought it last November.

 

[daperez13]

You may need to perform a flush on the heater core. What type and mixture of coolant have you been using?

I read somewhere about a blown resistor on the blower related to this issue. I do not have any more info on it but it might be worth researching to see if it applies to your vehicle.

 

[geopete]

You may need to perform a flush on the heater core. What type and mixture of coolant have you been using?

I read somewhere about a blown resistor on the blower related to this issue. I do not have any more info on it but it might be worth researching to see if it applies to your vehicle.

I'm thinking of the flush this weekend if I have time. Right now it has Prestone 50/50 mix in it.

I'll have a look, curious how a blower resistor would cause an issue like this. Still worth some investigation. Thanks

 

[geopete]

Still no heat. Well Luke warm at best until I start to drive it. Then it gets cold again. I'm thinking there must be an air mixing door somewhere under the dash for it to allow cold air in while driving. I read about them online here and there but nothing on where it would be located. Any ideas? Even if I could force the door closed for full heat over the winter I'd be happy.