2008 Impreza 2.5, Heat and A/C not working properly

[ThosL]

Seasonally, when the temperature changes, the heat and A/C will not work until the car is running for 20 minutes.  But it has to heat up for the heat to work.  Is this a coolant flow issue or wiring with moisture maybe causing this?  A friend wants to know. Is 20 minutes too long to get good heat or AC?

Edited December 2, 2019 by ThosL

[lmdew]

Sounds like normal operation to me.

 

[Mike104]

2 hours ago, ThosL said:

Seasonally, when the temperature changes, the heat and A/C will not work until the car is running.  But it has to heat up for the heat to work.  Is this a coolant flow issue or wiring with moisture maybe causing this?  A friend wants to know. 

Cabin heat is generated from engine coolant.  If the engine is cold there is nothing to transfer heat to the interior.  If there is a bad thermostat (staying open)  it can make the warm up time longer.  Not sure what vehicle you are talking about but if it has an temperature gauge it won't generally provide heat until the temperature indication is above cold.

In my case I have an idiot light for temperature (blue for cold, red for pull over now).  When the outside air temperature is colder it takes longer to heat up.

[heartless]

totally normal operation.

heat is provided by the flow of "hot" coolant thru the heater core - therefore the engine needs to be run and warmed up in order to provide heat.

AC also depends on the engine running in order for the AC compressor to operate properly.

 

[ThosL]

Thanks for the input.  I failed to include the 20 minute time it takes now for heat to come out.  I surmised thermostat when I spoke to him.

 

[heartless]

thermostat not operating correctly (or lack of one) can make warm up time take a lot longer.. and the colder it is outside, the longer it will take.

thermostats are intended to stay closed until the desired temp is reached in the engine, then they open to allow full circulation of the coolant. not having a thermostat allows full circulation all the time, which increases the time it takes for the engine (and coolant) to warm up and is actually detrimental to optimal engine operation.

and I hope you know not to use aftermarket thermostats in a Subaru..

[Rampage]

20 minutes is a long time for heat. I can feel warm air about 2 miles down the road in our 95 Legacy. Thermostat is probably stuck open or the heater core may be partially plugged on the inside or on the outside with debris.

For the A/C to take 20 minutes to work is unreal. It should a matter of seconds.

Does the vehicle have a "cabin air filter"?

I once had a problem with air flow in the 95. I had to remove the dash and then the a/c evaporator and heater core box. The fan blows air through the evaporator then the heater core then to the vents. I found the surface of the evaporator core was 3/4 covered with crud from leaves and dust.

Some newer vehicles have a cabin air filter to keep that from happening.

[ThosL]

I let him know, we work in the same company.  He should probably change out the thermostat with an OE or similar unit.  Thanks.