S_Johnson

So... my new a/c kit works great, but my vents are... odd.

I've searched, and everything I've found is about vacuum issues and the air only coming out the top, or everywhere at once, etc... I'm having a different (but maybe related?) issue.

My vents are super inconsistent. It's a firebird, so it has the two side vents, and the two vertical ones in the middle of the dash. The driver's vent puts out an "ok" amount of air, but nothing much. The passenger vent puts out almost NONE. The TOP center vent puts out a lot (but still not what I find in other cars), but the LOWER center vent puts out almost zero. How is that even possible???? They are just a cover over one big opening????

Even weirder, if I close the top center vent, still only a little comes out the bottom center vent, not nearly as much as came out the top before I closed it. This makes zero sense to me. Where the hell is the air GOING? I have SLIGHT breezes behind the dash (I took of the dash pad to poke around), but not that much, and I don't feel anything coming out the defrost or the floor vents, so I have no idea where it is all going.

Oh, and the side vent tubes are at least connected, I can see that much from the top of the dash, with the dash pad removed.

Is the issue with the center vents normal? What is "normal" here? I need a comparison.

S_Johnson

So, after some poking around, I understand why the bottom center vent doesn't put out much air, the angle of how the air goes through that area, means very little goes through the bottom vent.

My question remains, is this normal? Especially the passenger side vent? If I block off the center vent, I get more air from the passenger side, but still not much at all.

I need to know what "normal" is here. If the fan is on high, shouldn't I be getting a lot of air through ALL the vents?

someone972

iTrader: (2)

The HVAC system in these cars isn't great. The floor vents really don't put out much air, probably just due to restriction in the system (it appears to go through a couple tiny tubes). The side vents should be putting out a "reasonable" amount of air if the rotary switch is working. The passenger and driver side should be "approximately" the same. Certainly the most airflow will be out the top where the defrost is, but the little side defrost vents kind of suck. Certainly seems like the blowers in newer cars work much better, or perhaps they just have more efficient routing. I've always wanted to try and roll a custom HVAC ducting with electric doors, but thats more of an end-game sort of project.

84 1LE

iTrader: (9)

Some of the tubes use foam to seal around the vent & even with foam they don't have that great a seal, but I would check the condition of the foam.
Could also be there is a flap/door that is not closing properly & allowing air to escape elsewhere.There is more than one & hard to pinpoint.They also have a seal around the edge.

FWIW, on my Camaro the air coming from the vents on the center console (by radio) have never blown that much air.The two behind the radio are pretty good, but I cant really feel the flow, unless I put my hand in front.

Drew

iTrader: (58)

Plenty of possible causes... The fan motor could be going south, or it might not be getting full voltage, or it could be blocked by debris in the HVAC box. It's not uncommon for a mouse nest under the cowl grill to get sucked into the box. Might pull the fan motor and look around inside the box with a good light and look for anything it may have ingested. The same applies to the ducts, they can get plugged.

All of the vents and the HVAC controls run off vacuum aside from the hot/cold slider. If you've got a vacuum leak anywhere, it can keep the various doors in the HVAC box from opening/closing tight. A serious vacuum leak will make the HVAC default to defrost.

As mentioned, the HVAC ducting behind the dash mostly is connected by slip fits and butt joints, and there's a ton of foam rubber between various joints. By it's nature, Foam Rubber breaks down with age into a sticky gooey mess. Before it decays completely it just loses it's ability to spring back after it's compressed. Think about a falling headliner, it's the same thing, except that instead of the fabric falling down, the air being pushed by the fan can blow out between the joints. I'd check the other things first, because getting at the ducting is a pain in the butt, but if it comes down to it, the entire dash isn't that difficult to remove. The trick is removing the fewest bolts possible, and removing it as an assembly. Even then it's probably not a job for the inexperienced.

Replacing the foam rubber and removing obstructions, as well as making sure the fan is running up to a proper speed, should result in a system that works the way it did new.

Drew

iTrader: (58)

I forgot to mention, the A/C evaporator is sealed to the housing under the hood with foam rubber, as is the fan motor, and the blend door in the heater box under the dash is sealed with foam, etc... All of the above can break down.

S_Johnson

I'm going to test supplying straight 12v from the battery for the blower motor, and see if that helps. I've already replaced the motor itself, and it was exactly the same.

I suspect I'm just going to have to pull the whole thing this winter and go over everything, fix all the seals, etc...

The main thing I needed to know, was if almost ZERO air coming out of the passenger side is normal. Sounds like it's not.

I'm not joking, you can't even really feel it with your hand up against the vent on the passenger side. The driver's side has "some" but not all that much.

S_Johnson

I already dealt with the evaporator seals, since I just replaced the evap, and everything else under the hood (classic auto air stage III kit).

paulo57509

Is this a kit that retrofits AC into a car that originally didn't have AC?

S_Johnson

No, it's the kit that replaces everything with modern stuff designed for 134A.

My kit was the "stage III" that included everything. Modern-style compressor, custom mount, new hoses (without that god-awful double-hose mount style on the compressor!), new parallel flow condenser, new hard line, new evaporator, new dryer, new cycling switch. If refrigerant touched it, this kit replaces it.