JJ77

I have a 1996 Vette.

I get heat and AC out of the defrost and the floor vents but not out of the dash vents when I put the controls on the dash vent mode. When I put the dash vents on, I still only get air flow out of the defrost and floor vents.

Why would I not get air flow out of the dash vents when it is in this mode?

Thanks,
JJ

redvette6spd

i have exactly the same issue with my 96

flannel_man

BUTCHANDHIS96C4

This is usually caused by a vacuum leak.

The first thing I would check is the vacuum "T" under the passenger side fuel rail cover. The part is about 6 bucks and is usually in stock @ the chevy parts dept. It's made of plastic (stupid, should be some other material that can resist heat damage like aluminum) and will disintegrate with time. Pull the cover off and it's easy to spot.

The second is a leak @ the controller which is under the dash on the driver's side. If it's this, it could be bad / leaky lines or the controller itself going bad. Get a shop manual it you find that it needs replacing. If I remember correctly, It's a little tough to get to.

RainJ

It is either a Vac line under one of the fuel rails that has started leaking or cracked or its the junction box under the driver's side dash.
(usually can lie on your back with your head and chest under the steering wheel and your legs out the door (or up in the air) and check it out.
Should be several Vac Lines all meeting into one box. Those connections usually wear loose over time and need re-seating.

Not an uncommon problem you have,
Rain

1Patriot

Welcome to one of the most common problems with the late version of the C4. Sounds like you are ready for an AC Controller and laying on your back under the drivers dash. Shop around ig you intend to do the work yourself; the controllers are not cheap from GM.

Frizlefrak

If you don't have one, get a vacuum pump with a gauge. Test each vacuum line, starting with the source line under the hood. If each holds vacuum, disconnect the vacuum line cluster that goes into the control unit and test each individual vacuum motor. Each should hold vacuum and actuate when you apply vacuum. If all your lines and vacuum actuators are OK, the control unit is bad.

RainJ

like this one?

http://cgi.ebay.com/ebaymotors/ws/eB...category=43989

Frizlefrak

Ummmmm, not exactly. That is just the gauge, and it will test vacuum with the engine running. What you need is something that you can pump up by hand....like this

http://cgi.ebay.com/ebaymotors/ws/eB...category=43989

You can buy these at Pep Girls or any parts house for about $30, and they come in very handy. I have found and fixed more tiny vacuum leaks on my old Vette than I ever imagined possible.

RainJ

Thanks, my friend.

Will certainly come in handy!