2008 buick allure

[privatecoach]

When car is on a/c plenty of air comes from the dash vents. However, when you switch from a/c to heat then there is hardly any air that comes out of dash vents. I also had a slushing noise coming from dash when turning corners.
I had heater core back flushed and that took care of the slushing noise in the dash. However I took back to the shop and told them there is still hardly any air coming from the dash vents when using heat. They verified the problem but have no idea what is causing it. they checked the operation of the blend door and it works as it should. Any ideas?

[brcidd]

Uhm---Urgggh--- That is the way it is supposed to work-- cool air to face when vent is selected, and warm air to feet when heater is selected.....the heater always directs air to floor, the vent always directs air to face. If you want hot air to face- which many don't- then select vent and raise temperature control to red or hot.. If you want cold air to feet- which many don't- then select heater and lower temperature setting to blue...

Not sure what you expect......

"Heater" means air goes to floor

"Vent" or a/c means air goes to panel vents -- don't expect the air to come from vents when you tell it to go to floor.....by selecting heater......

[privatecoach]

To the guy (brcidd) with the rude response not sure you know what your talking about. Let me rephrase this to simpler terms for you. No matter what selection you choose the air is restricted coming out. So even if it is at your feet or on defrost air is restricted. However only restricted when turning to heat. When in cold it is not. I look forward to your next comment.

[brcidd]

"by turning to heat" . Do you mean raising the temperature (blue to red on temp door setting) or by switching the mode select button to "heater?"

definitions may help:

blend door- the door that puts heat to floor and some or all to defrost. some systems call the temp door blend door

temp door. the door that directs air flow through or around the heater core, that adjust the temperature of the output air, Note-- all air flows through the evaporator core. then either through or around heater core, depend =ing on position of temp door.

mode door- the door that determines if air is to go to floor, or to panel vents, or to defrost through blend door.

recirc door- the door at the air intake side of HVAC module that determines source of air- either outside air or inside air- CFM of air flow is increased when using inside air due to shorter air path- less restrictions- sounds louder too.

Is recirc door functioning? I've seen plastic wraps/bags sucked in air intake of recirc grid such that it blocked all air flow while only in recirc- but worked fine with outside air commanded. Remove your glove box and look at air intake of recirc door...to know for sure.

Do you have auto climate control? (ATC has a digital temp display)

recirc door opens and does come on when a/c is on and full cold temp is selected and can come on when heat and full hot is selected- but is NEVER open when in defrost mode. This is for safety reasons to be sure to clear the windshield. Defrost can only use outside air to clear windshield- does not work with inside air- will fog the windshield uncontrollable when 41 to 50 degrees out and raining. So a restriction may be on the inside air path if defrost air flow is good....

with that being said...

If defrost air flow is bad- then restriction has to be on outside air inlet side- like up in cabin filter- or leaves or fluff in screen under hood cowl at windshield wiper cowl.

they verified the blend door- which is not the recirc door....

[privatecoach]

On this car I have dial for fan speed, dial for temp/cold/hot and then dial for vent location such as dash defrost feet

I do not have ATC on this vehicle.

The mechanics told me all doors/actuators are operating as they are suppose to.

However, I will say that yes even when the defroster is used air is still restricted when on hot versus cold it works fine

I also thought maybe cabin air filter however when on cold does the air still pass through filter? or is it just on the hot when it passes through?

I have not checked the cabin filter or the cowl up under hood yet that will be next

Thanks for the help it has been driving me crazy and even more so when the shop could not figure it out.

[maxwedge]

All the intake air goes thru the cabin filter. To add could be a varmint nest in the ducting.

[Blue Bowtie]

Originally Posted by privatecoach

Any ideas?

Yes. There may be accumulation in the heater core (air side) restricting flow. This could be a filter, as Max alluded, or contamination on the core itself. One may have presumed the shop performing the analysis would have some understanding of the system and investigated this possibility.

FWIW, there is a distinction between a "rude" response and a "frank" response. We tend to be direct and straightforward here.

[brcidd]

Most mechanics would have checked the filter(s) and cowl inlet first. It has been my experience that even dealership mechanics don't get it right. They don't have the incentive to figure it out.