AC/Heater Poor heating when it's cold outside - Civinfo
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post #1 of 3 (permalink) Old 19th April 2019, 01:19 Thread Starter
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Poor heating when it's cold outside

I have an automatic AC and during cold weather I can barely warm up the car (cabin temperature). When the temperature falls below around 10C it gets harder and harder to warm up the cabin. Last year when it was -10C I was driving in a thick sweater and I was still cold...

The engine temperature gauge gets to the working temperature (around 1/3 of the gauge like always) quite fast, after around 5 km/3 miles when it's 0C, and it stays there.

The only way to at least somewhat warm up the cabin is to set the fan speed to 2 bars, the temperature to 24-25C and fan direction to body and feet, regardless of turning the AC on or off.

I noticed that during warm weather the engine fan turns on and off very quickly if the car is running idle and the AC is on (every 30 seconds for around 5 seconds). If I turn the AC off, the fan doesn't turn on. The mechanic checked the thermostat with the tester and said it was working fine.

Could it be the ventilation flaps? If I for example set the fan direction to head and feet, it doesn't entirely stop to blow into the body, but it starts to blow cold air very slowly.

Some of you mentioned the coolant level - I checked it and it was OK. Should I bleed the whole system and fill it with fresh coolant?

On the other hand the AC cools like crazy when it's hot outside. Today it was 20C and I had to set it to 24C.

I have this Civic for 2 years now, so I don't know if it was heating fine before.
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post #2 of 3 (permalink) Old 21st April 2019, 17:47
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Do the diagnostic checks at the bottom of this page

What are the sensors reading from these checks? Are the values reasonable given the outside temperatures?

My temperature gauge reads right in the middle so yours may be a little low. Is the thermostat sticking open? Failing that, may be a blocked heater matrix.
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post #3 of 3 (permalink) Old 27th June 2019, 17:52 Thread Starter
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I did the diagnostic check and the first one gives normal values (as far as I'm concerned) and the second one reports only ''88'', so everything should be OK.

The thermostat is OK - at least my mechanic said so, but I don't know if he tested it or just tried to run the car idle with A/C on and off. When A/C is on, the fan starts to run in the same pattern, almost regardless of outside temperature - it starts approx. every 30 seconds for 5 seconds. When A/C is off, the fan doesn't start at all, which at least in my opinion means, that the thermostat is OK.

What about blocked heater matrix - how can I test that?
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