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Ron Z.
Ron Z., - Chevy Tech -
Category: Chevy
Satisfied Customers: 18863
Experience:  18+yrs experience. State Inspector and Chevy Diagnostics
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The AC doesn't blow air from the front dash board. it ony

Customer Question

the AC doesn't blow air from the front dash board. it ony blow air from the defrost and the floor, and it doesn't change the air flow when I change the switch.
JA: How is the air flow? Have you checked the hoses?
Customer: Which hoses?
JA: Tell me a bit more about what's going on so he can help you best.
Customer: I checked the blower motor, and the compressor. they are both working. The problem is the air doesn't change the direction when I change the switch
JA: Are you hoping to fix this yourself?
Customer: the direction of air
JA: Is there anything else important you think the Chevy Mechanic should know about your Chevy?
Customer: yes, I will fix it by my self
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Chevy Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Chevy
Expert:  Ron Z. replied 1 year ago.

May I have the year and model of your Chevy?

Customer: replied 1 year ago.
chevy lumina 1998
Expert:  Ron Z. replied 1 year ago.

Great, thanks. Give me a minute to load in your vehicle and grab some images for you. Be right back...

Customer: replied 1 year ago.
Expert:  Ron Z. replied 1 year ago.

Ok. When the flow of air will not change direction of output, this is most commonly due to a vacuum problem. On this vehicle, the mode doors are vacuum operated. So when you re-direct flow, the solenoid applies vacuum to move the door internal of the HVAC housing. So, first carefully inspect the vacuum lines. Very common for a line to have a crack or hole. Inspect the linkages between the valves and the HVAC case and make sure they are in tact. These items are located under the passenger's side dash. Remove the lower panel for access (image below). If these all check ok, check the vacuum reservoir tank. It's located under the front of the vehicle (image below). Inspect the tank for any cracks or holes. Again, inspect the vacuum lines for any cracks, holes or disconnections. If you are sure there are no leaks in the system, suspect the electric solenoid.

Vacuum Line image:

Vacuum Tank image:

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Customer: replied 1 year ago.
For Inspecting the linkages between the valves and the HVAC case. Do I need to remove the gloves box?
is vacuum reservoir tank on the hood or under the dash board?
Expert:  Ron Z. replied 1 year ago.

The linkages should be visible from under the passenger's side dash. You may need to remove the glove box to view the defrost linkage.

The vacuum reservoir is located under the vehicle, driver's side (as shown in the image above). This is where you should carefully inspect. Due to it's location, the vacuum line has a great chance of being damaged. I've seen the vacuum line-to-tank connection completely broken off before. And the vac line from tank-to-solenoid is very long, so strong chance of a crack or hole- inspect this line carefully (you can see it in the image above coming off the right side of the tank and then curving all the way around to the passenger's side. Poor design)

Expert:  Ron Z. replied 1 year ago.

Hi. I noticed this thread was still open, so I wanted to check in and see how you made out? Did you find the problem? Did you have any other questions on this issue?

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