ted13b

I'm stuck on this heater door problem. It looks like something is missing here. I believe this door sends heat to either the lower or upper heater/AC ducts. I ordered the vacuum actuator, but it's just the cannister, no brackets, etc. I've looked in the shop manual and AIM, but I can't find a good pic or ilustration of this area. Anyone else have their dash apart?? BTW, it's a 77 L48, AT, A/C.

hunt4cleanair

So what happened to the original brackets and cannister?

The system works off vacuum so even with a new actuator (cannister), doors won't operate if the vacuum system has been compromised. A vacuum pump can help troubleshoot vacuum including testing actuators. Not sure if that helps but went thru my 78 system a few years ago when I replaced the heater core...so familar with the system.

ted13b

I don't know what happened to the original stuff, I found it like this while checking the heater system to find out why the footwell area was so hot.

hunt4cleanair

Are the vacuum lines to the door gone as well? There is also an actuator at the passenger fender for fresh air...is it there? And another below the defroster vent...what about it?

What about the duct work? Control lines to the A/C heat control under the driver's console dash?

rbowman

http://www.corvettemagazine.com/inte...x-rebuild.html

Check this one out. If I remember correctly this one is controlled by the cable, there should be a bracket mounted on top and to the right side should be where the cable attaches (check picture on step #22). Rebuilt mine last year but never took pictures.

Ron

Ron

JimT

There is supposed to be an arm connecting the white bracket on the door - where the screw is - to the heater vacuum actuator.

ted13b

The temp cable from the heater control moves an inner door. It seems like something, either a cable or vacuum actuator, has to open that touter door, but it's not visible in those pics either.

ted13b

After doing a little more research, including the tech info on Wilcox's web site, it appears that this door operates from a vacuum actuator on the firewall side of the heater box, rather than the passenger compartment side. I guess I need to spend some more time under the dash to find out why it's not opening...

captl27

I think anyone that own a c3 should at leasted own a service manual and a assembly manual year specific for there vehicle. I am not sure about a 77 manual but my 79 has quite a bit of information on the vacuum/heat/air conditioning systems.

08vycpe

There are two doors that get actuated. One is the mode door that directs air either at the bottom, the A/C vents and/or the defrost. The other is the temp door that controls the flow of hot air to the cabin. I think the actuator under the hood on the box is the temp door operation and the one in the cabin is the mode door.

As mentioned, the operator should be fully described in the service manual aas well as pics in the AIM.

hdpete98

This is your mode door and is vacuum controled. It is conncected to a vacuum actuvator on the back side. You would need to remove heater box to get to it. The temperature is controlled by a cable that is on top of the heater box. It has a spring on it and should be visible if you pull passenger duct.