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Malfunctioning heating system in 2009 Impala

I live in North Carolina and have a 2009 Chevy Impala. On cold mornings I like to start my car so that it’s warm inside and the windows are defrosted. Starting late last winter, although the engine warms up, the interior of the car no longer warms up and the rear defroster works sporadically. As soon as I start driving the interior warms up within a mile, but the first mile with the fogged windows is dicey. Also, I haven’t tested it thoroughly yet, but it seems that the interior won’t warm up even if it’s in gear and I’m sitting still - the car has to be moving. What might this be?

It may be a thermostat problem. It could also be a blend door problem under the dash. Hard to say without being able to look at it.

Since this is a fairly new car, start with simple things first. You might have “air” in the cooling system. Perhaps from a loose hose clamp. While the motor is cold one morning before you start it, look at the overflow coolant tank. Is it empty? 1/4 full? Just what is the level of fluid in the tank? Then find the radiator cap and remove it (only do this when the motor is cold). Is there fluid visible just under the radiator cap? There should be coolant right up to the radiator cap and it should be easy to see it.

If you don’t see fluid at the radiator cap, get 50/50 mix of the proper coolant for your car and top off the radiator and replace the radiator cap. Then if the coolant overflow tank isn’t about 1/2 full, add the same 50/50 mix until it is. Now you can start the motor. You might notice a difference immediately, or you might have to repeat this process a couple of times to get all air out of the system.

Even if the heating problem is resolved you aren’t done. The problem really is how did the air get into the “closed” cooling system? That might be evident if you can see a leak somewhere. If not, you should have the cooling system pressure checked to locate the problem and correct it.

Thanks for the suggestions. It’s pouring rain here today, but I’ll try that as soon as I can. Would that account for the rear window defogger not working or is that a separate/related problem?

The rear window defogger is a set of electric wires to heat the back window. It is separate but if the cabin is full of moisture it makes the job of the rear defogger much more difficult. In that way they are related.

If you turn on the defogger you should see where the moisture near the wires is clearing off. If that isn’t happening then the defogger isn’t working either, but the fix is independent of the no heat from the heat/AC system.

@mwrg: I second the thought that a low radiator could be the problem. I thought I’d add that if your radiator is low, you want to make sure you use the correct coolant in it–you cannot mix orange and green coolants. If you do, it will cause a chemical reaction that will really gum up your cooling system. Your 2009 probably has “Dexcool” in it, so you need to use either Dexcool or a universal coolant which is formulated to mix with all types of coolants. Also, systems that use Dexcool do not survive well when they are low and there is air in the system. Air makes this type of coolant degrade into a sludgy mess. If your system is low, I’d consider having it scrutinized for leaks, and flushed and refilled.

On These Cold Mornings, Are You Starting The Car With The Factory Remote Starter ?

Many (Most ?) 09 Impalas will control the heating system plus rear defogger or air conditioning system for you to make the car comfortable when you use the remote start. When you get to the car and put in the key then the system controls return to normal manually regulated mode.

I was thinking if the problems are present when starting remotely without the key, and not when starting with the key, the fault could be in whatever controls the climate (BCM - Body Control Module ?) and not necessarily with the heater, A/C, or rear window defogger.

Does this fit with your experience ? Does everything work right when cold starting, using the key, from inside the car ?

CSA

Thanks for the tip about the coolant, Oblivion. CSA, the problem starts when I start it with either the key or the remote.