a/c recirculation mode

titanium10k · June 8, 2005

I have an 02 silverado and Im having a problem with the ac not going to recirc mode. I just started having this problem that the ducts will not close at all when i push the recirc button. The light comes on but it is still outside air, even shut off ac and fan when traveling down the road and hit the recirc button and light comes on but air is still flowing. This is all with the temp on cold and the duct on the setting for the front vents. The reason I noticed this is because when on the outside air function the fan dosnt blow as hard and its harder to cool down. any help is appreciated....

GM-Tech · June 9, 2005

We have a fair amount of actuator problems. Someone needs to plug in a scanner and take a look at the door position data, check for DTC's, etc.

patyukon · June 14, 2005

I have an 03 Yukon and an 05 Sierra (not hd) crew 4x4. Recirc doesn't seem to work on the 05 as it does on the 03. When I put the 05 in manual mode and press the recirc button, the little indicator light comes on for a few minutes but there is no noticible change in air volume or temperature. When I do the same thing on the 03 there is a definant increase in air speed and a drop in temp. Dealer says it's normal computer control due to shift to electric fan on the 05 versus the mechanical clutch fan on the 03 plus moisture buildup sensors in the condensor overriding recirc in humid conditions. Bottom line is the 05 a/c is not nearly as effective as on my 03. Is the dealer tech feeding me a line or is this true?

titanium10k · June 14, 2005

patyukon on my 02 it used to work like your 03 that when u put into recir mode the volume would increase as well as the temp would get colder that is how mine used to work.......and why would moisture sensors override recirc you think it would put into recirc to dry out the air inside the cab continously instead of outside air???

GM-Tech · June 15, 2005

Dealer says it's normal computer control due to shift to electric fan on the 05 versus the mechanical clutch fan on the 03 plus moisture buildup sensors in the condensor overriding recirc in humid conditions.

I hope you weren't buying this line. There's a whole bunch wrong with that explanation.

First, I don't see what difference electric fans vs. engine driven would have. In fact, I believe you would have MORE airflow during low speed driving, unlike an engine driven fan which depends on engine speed and this would be more noticeable at idle. Above 30 or 40 mph, it wouldn't matter either way since there's enough forced airflow that you could probably just throw away either type of fan and never notice.

The condenser sits in front of the radiator. What the heck would be the purpose of a moisture sensor? What happens when it rains? Even if they meant the evaporator, which is likely, there is no such thing as a moisture sensor there.

I know the perception is that recirc gives you more airflow due to higher fan speeds or whatever, but there's really not much difference. It SOUNDS more forceful because the recirc door opens to the cab and you're hearing the air being sucked from inside the cabin. When it's drawing it from the grille outside, under the windshield as in non-recrirc mode, you don't hear that. I suppose the aerodynamics of where the air enters may make some difference in the volume of air. The advantage of recirc is that the A/C is cooling air that already been cooled some instead of constantly trying to cool 90 degree air, or whatever your outside temps are.

Here's a brief description from our service information on the recirc mode in an '05 Silverado...

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle. Regardless of the blower motor switch position, recirculation is available only in the panel and bi-level mode switch positions. Including the OFF position. The mode switch must be placed in either the panel or bi-level position before the blower motor switch is placed in the OFF position. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost or defog positions. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. If the HVAC control module detects a fault with the recirc door the HVAC control module will try to drive the actuator for a predetermined amount of time, to outside air, which is the defaulted position for the recirculation actuator.

patyukon · June 16, 2005

No, I wasn't buying this line at all... I just needed some ammo. I've printed this and I'm gonna pay a little visit to the dealer. Thanks!

Dealer says it's normal computer control due to shift to electric fan on the 05 versus the mechanical clutch fan on the 03 plus moisture buildup sensors in the condensor overriding recirc in humid conditions.

I hope you weren't buying this line. There's a whole bunch wrong with that explanation.

First, I don't see what difference electric fans vs. engine driven would have. In fact, I believe you would have MORE airflow during low speed driving, unlike an engine driven fan which depends on engine speed and this would be more noticeable at idle. Above 30 or 40 mph, it wouldn't matter either way since there's enough forced airflow that you could probably just throw away either type of fan and never notice.

The condenser sits in front of the radiator. What the heck would be the purpose of a moisture sensor? What happens when it rains? Even if they meant the evaporator, which is likely, there is no such thing as a moisture sensor there.

I know the perception is that recirc gives you more airflow due to higher fan speeds or whatever, but there's really not much difference. It SOUNDS more forceful because the recirc door opens to the cab and you're hearing the air being sucked from inside the cabin. When it's drawing it from the grille outside, under the windshield as in non-recrirc mode, you don't hear that. I suppose the aerodynamics of where the air enters may make some difference in the volume of air. The advantage of recirc is that the A/C is cooling air that already been cooled some instead of constantly trying to cool 90 degree air, or whatever your outside temps are.

Here's a brief description from our service information on the recirc mode in an '05 Silverado...

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle. Regardless of the blower motor switch position, recirculation is available only in the panel and bi-level mode switch positions. Including the OFF position. The mode switch must be placed in either the panel

or bi-level position before the blower motor switch is placed in the OFF position. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost or defog positions. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. If the HVAC control module detects a fault with the recirc door the HVAC control module will try to drive the actuator for a predetermined amount of time, to outside air, which is the defaulted position for the recirculation actuator.

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GM-Tech · June 16, 2005

No, I wasn't buying this line at all... I just needed some ammo. I've printed this and I'm gonna pay a little visit to the dealer. Thanks!

Oh boy, they're going to love me. I'd say most service departments aren't interested in stuff you find on the internet. I'm actually the same way. "Oh jeez, here comes another guy with something he found on the internet that doesn't even apply to his vehicle."

patyukon · June 17, 2005

I think the tech will listen to me and have a positive attitude (at least to my face!) My approach to problems like this is always low key, not going at him like a loud, know-it-all a-hole.... If he still thinks nothing is wrong, it's simple...I'll take it to another dealer. I'm lucky, there are several located fairly close to me. Folks like you really help guys like me. Thanks for your opinions!