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11

My top suspect would be a radiator fan that isn't running when it should. The fans assist in transferring heat from the radiator to the surrounding air, and are most needed when the car is stationary. This doesn't mean that the fan is bad. It could be that the relay is malfunctioning or there is a break in the wiring somewhere, so I would try to rule those ...


10

This is normal behavior. The A/C system is turned on to dehumidify the air, which causes the windshield to defog. Without it, your breath would freeze on the inside of the windshield and cause further issues. EDIT: Please note Bob Cross' comments below. I found instructions on the Honda Tech Forum which is supposed to give you full manual control over ...


9

You are correct that the only extra energy consumed is the electricity used by the blower fan to move the warmed air. In the grand scheme of things the extra fuel required to generate that electricity is miniscule. The coolant is circulated regardless of the heater setting. Moving the selector to cool or warm merely directs all the air over the heater core ...


9

Let's do a little back-of-the-envelope calculation: Assuming that the heating unit has an efficiency close to 1.0 and that automotive diesel has an energy density of ~39 MJ/l which translates to ~10kWh/l. With no knowledge of your pre-heater, let's assume 5kWh. Thus, 0.5l/h, i.e. comparable with a warmed-up engine. Now, the diesel engine has a lower ...


8

As for the blower only working on max, that screams resistor pack. It's usually in the passenger foot well near the blower motor itself. Sounds like it's held in by two 8mm bolts in your case. Shouldn't be too terrible of a job, but you might want to avoid it if you've got back or neck problems. I usually put the seat back down as far as it will go and ...


8

Here's a nice tip: if you turn up the heat in your car, it helps lower the operating temperature of your engine. Sometimes by as much as 10%. Not a problem when you're driving around in icy cold weather, but if your car is overheating, turning on the heat, opening the windows and putting the blower on full could save your engine from popping a gasket. If ...


7

Problem solved! The key was to finally locate the source of OBDII code PO 0171, left bank lean, which I realize was not part of my original question. Anyways, I found a leaky air hose connection between the manifold and the MAF, once I corrected it, the engine idle smoothed out and now we have heat as designed at idle.


7

Check the coolant temperature if you can (if it's an OBD-II car, some readers can give you coolant temperature). If you've got a coolant temp gauge, see if it looks any lower at all (most are pretty hard to read though, one tiny tick down can be a HUGE difference in coolant temperature). I suspect a failed thermostat that's sticking open. I had that ...


7

It's possible that the impeller blades on the water pump are either compromised or gone completely. I ran into a somewhat similar situation with a Chrysler. The engine would not overheat driving. Idling it would overheat eventually but it took a long tome to do so. The heater core would not get hot no matter what I did. The thermostat was already replaced. ...


7

Does the air conditioner work? If so, you can blow COLD and DRY air onto the windshield from inside by setting the controls to: A/C, WINDSHIELD, OUTSIDE AIR. The cold/dry/outside air from the A/C will prevent the warm/most/inside air from you from getting to the windshield and condensing/freezing. Even if you don't have A/C, you can try with just cold/...


6

It looks an awful lot like you have diagnosed all of the really hard problems and come up negative. I wonder if you have a simple mechanical problem: is the linkage sound between the hot / cold selector and the flapper valve that forces air past the heater core. From what I hear, the foam around the flapper is also prone to disintegration in humid climates:...


6

It turns out the problem is pretty common with 3.5L Impalas. For some reason these engines lose coolant. Some blame is placed on head gaskets, some blame Dex-Cool. What ever the cause, refilling via the overflow jug can leave an air pocket in the cooling system. The cure is to fill via the pressure cap right to the top. Recheck the level after several heat/...


5

Several Possibilities Low Coolant Level Partially plugged up heater core Partially obstructed heater valve Weak water pump


5

Does your car overheat too? If so, you could have a faulty thermostat, an air pocket in your cooling system or maybe even a leak somewhere. My truck's heat would only work while I was driving, then stopped working altogether while the engine started to overheat. I changed the thermostat, then the heat would blow hot/cold/hot/cold, I didn't realize you had ...


5

The cheapest way to do so, would be to add something like this aftermarket accessory. Looking for any in-dash options would likely be more expensive.


5

It takes a long time for the heat gauge to register as anything but cold, about 10-15 minutes. This is almost definitely a stuck open thermostat. The engine should reach operation temperature within 10 minutes, meaning middle of the gauge. You should see it start moving up within about 5 minutes


5

If you mean the rear defrosting wires in your rear window, you should be able to turn it on immediately as it's electrically based. If it's making a noise, I suspect it's the circuit breaker that automatically turns it off based on heat, and you should look into replacing it. What make/model is it? If, alternatively, you have some sort of auxiliary/rear ...


5

If the thermostat is stuck open, you would get the symptoms you describe. A thermostat stuck closed will cause overheating.


5

Check the overflow tank on the radiator when the car is overheated. If that tank is full, you've probably got a blown headgasket - that's how I spotted mine. For the thermostat; did you buy an OEM one, or after market? Foresters are very particular about the thermostat, and ONLY the OEM ones work reliably.


5

Coolant flow through the heater core is restricted, which means the fan is able to cool off the water in the heater core before it is replaced with warm water. There are a few possible causes for this A water pump that is not pumping at full capacity. This can happen when the water pump impeller corrodes away Corrosion blocking the inside of the heatercore....


5

Well, this is a question for a Canadian guy. Here's the thing: in extreme cold (-20C and colder), the moisture coming off your breath will condense as ice and fog on the inside of your windows. Air circulation, whether cold or hot, will help with the fog part your engine does not need to be at operating temperature to defrost your windows, even just a ...


5

You are right that the heater in internal combustion engine powered vehicles usually uses the waste heat of the engine for heating – that's why in the summer you can use the heater to get a bit of extra cooling if you need it. During the winter the cooling from the heater may slow down the engine warming up, but only by a tiny bit. Until the engine comes up ...


5

When the engine was changed, was the heater properly bled when the cooling system was refilled? If there is an air-bubble stopping coolant from flowing properly through the heater, that would create exactly the symptoms you are describing, yet may not cause any overheating issues if the rest of the cooling system is working correctly.


4

The heat problem sounds like poor coolant circulation, possibly due to low fluid level or partial clogging.


4

You may have air trapped in the cooling system. The air needs to be burped out. The method varies by make, model, year, etc. Due to variation between models can you tell us what country the car was made for?


4

It depends on the vehicle, why it is being left, and how it is prepared before being left. If it's a vehicle that's in reasonably regular use, then I'd recommend making sure it's used at least once every week or so, and is driven far enough for the engine to get up to full operating temperature. Just starting it and letting it run is better than nothing (e....


4

I had a similar problem with my 2000 Ford Focus last year. I can't remember what it was called, but basically it's a thermostat that's sits against your radiator that turns on the radiator fans when not enough air is flowing through the radiator. Like when sitting in traffic. Look for wires running from the radiator to the fans. They sit right between the ...


4

I had a problem with my VW Golf overheating. I also changed various parts, the thermostat being the first as that controls the circulation of the coolant. In the end I found the cause, the system wasn't pressurising as the o-ring on the filler cap had a kink in it and therefore wasn't making a good seal. I straightened it out and then it worked. Lesson of ...


4

bad air duct door You have multiple air duct doors in your car. One of them will control the air from your heater. You may have situation where the servo motor is bad in a particular door. Sometimes you can have a situation where hot air comes out of one vent and cold air comes from another and various combinations of the issue that maps back to a bad ...


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