AC issues... should be simple.

[ChiefGoFor]

1991 Chevy Lumina, 3.1

It seems that I am having a little issue with my AC. I recently replaced my battery and now my AC is only partially working. The AC will blow out of the floor and up at the window, however, it will not blow out of the front vents.
I have been told that there is a flap that when you push "AC", "Max", or "Vent" that routes the air out the front vents. I have also been told that there is a vacuum line that is most likely loose. Can anyone confirm this?? If so, where do I find this line to check?

If I am way off on this, please try to set me straight. I have checked the fuses (all of them).

Any help is appreciated. Thank you very much!

[corning_d3]

Sounds like a vacuum line.. Here's a vacuum diagram.

[ChiefGoFor]

corning_d3,
That's great news! Unfortunatelly, it only gets me half way there. I have no idea where to find that in my car. I know the basics to car repair (meaning, I can identify all the major parts, blah blah). So, some time today, I will take a snapshot under my hood and hopefully that will help give me some direction.
Thank you so much for a quick reply (I thought it would take a little longer).

[richtazz]

The distribution block in Cornings diagram is on top of the throttle body (its the oval shaped rubber piece with the 3 or 4 plastic tubes coming out of it). The vacuum line he is pointing out runs under the air filter assembly, and may have come disconnected or cracked while you were replacing the battery (as the battery is tight against the air filter housing). It goes to a vacuum storage canister (shaped like a ball) on the firewall, then to the HVAC system for control of the mode valve that switches from floor to vent to defrost, etc...

[ChiefGoFor]

Ah, so that is what that line was for?!?!

I guess I should give a little background on the reason for the batter change. It was foaming up by the post. So, I cleaned it up (then later realized that was not enough and that I needed to replace it). I had noticed that it had dripped on a "wire" below and severed it, but everything worked, so I did not think too much of it. While replacing my battery, I thought, "I will splice this line and reconnect it". To my surprise, it was hollow; no wire! So, I let I just ignored it, thinking that it worked before... Anyway, so I guess now I know.

Is this a part I can purchase at an auto parts store? Anyone know what an appropriate name for it is? How come it worked before when it was severed? I'm thinking that the end was cauterized shut somehow. I doubt taping it up would fix it.

Thanks for the responses.

[ChiefGoFor]

Okay, I owe this forum big time! I used electrical tape to tape up the end and just like magic, it works! I am still curious to know if there are any side effects to this. I figure that it was like this for at least a month or so when it was cauterized, so it should not be too bad. If this works, then what is the real purpose of the "vacuum storage canister"? Thank you to everyone!!!

[Blue Bowtie]

The vacuum reservoir maintains vacuum to the HVAC system controls when the engine is under a load and not producing at least 12" Hg of vacuum. If vacuum were to drop, the dampers in the HVAC system would divert all air flow to the default position (defrost) as a safety. This happens frequently during prolonged driving up hills or other sustained medium to heavy load conditions.

Oh - I see you're in Nebraska. You don't have any hills, so you might not notice it.

Instead of electrical tape, you might try to use a larger piece of hose to splice the broken section. It'll be more permanent. At least you found the source of the problem.

[richtazz]

The vacuum storage canister gives the HVAC unit constant vacuum. Engine vacuum changes with throttle, so the canister stores vacuum for full throttle moments. You can buy a small piece of vacuum hose whose ID is the same as the plastic tube's OD and spice it in to use a permanent repair. The tape will start to leak sooner or later and cause your HVAC to default again.

You are welcome.