My 70 non a/c car has the original astro ventilation assembly and I noticed it is always open and is not closing. There is an actuator of some kind hooked into the god awful vacuum system that these cars have. I guess that might be the problem but I was wondering if anyone has just blocked off these vents? I see the A/C cars have a block off plate in them. Any thoughts on this? I will probably attempt to get it working but I do not want water coming in the deck vents. I washed the car and the back was soaked. This is how I noticed the vent seal not working.

 

Although I can't offer any suggestion on sealing the vents I will mention that with the motor off the vent doors are open. So regardless of if your system is working or not, it's the same as the others when washing

The vents open into that trough and should drain any water out into the two rear wheel wells. Unless your really pouring water into the rear vents they shouldn't run into the rear compartment.
Maybe check both sides and see if the drain tubes aren't plugged with leaves etc.

But anyway that doesn't help with your question. You could disconnect the vac-can on the drivers side of the vents and wire them closed. As long as the seals are in good shape it will help keep the water from soaking the rear compartment but I still suspect the drains are plugged.

Or it's possible the two rubber tubes that connect to the drain ports in the wheel wells are torn/missing
M

 

Thanks. I will take a closer look and see whats going on. The car is so nice I will probably do whatever is needed to fix this. I try to keep it nice. I have owned it for 30 years and never noticed water coming in so maybe its something ez to fix. Thanks for the reply, I will check those drain lines. I just had a new custom exhaust put on the car and maybe they knocked a drain line loose or something.

 

The new exhaust sure came out nice though huh?

 

Hi L,
Actually the system itself and vacuum supply for the Astro Ventilation actuator is pretty simple.
It's a single line that runs back along the transmission tunnel from the heater/defroster controller to the actuator.
It's controlled by the right side cold/hot wheel on the controller. When the wheel is at C the door is open, and it's closed when the wheel is at H.
It begins as a rubber line, changes to a copper line and then changes back to a rubber line at the actuator.
The rubber drain tubes for the plenums are readily available but are a bit of work to change because of how they are mounted at the wheel wells.
Good Luck!
Regards,
Alan

Exhaust looks VERY nicely done!

 

Vacuum systems are simple. It's the understanding of them that is 'difficult'. Fear of the unknown keeps a lot of folks at arm's length on the C3 vacuum system.

One source of vacuum...the engine. Differential pressure to atmospheric (ie, a vacuum) can do 'work' if applied to a vacuum "motor" (servo can, switch, actuator, etc.). Since vacuum is already available as a by-product of engine operation, it's already there to use; and as long as the engine is running, you have it. If the engine is NOT running, you don't need it anyway.

Vacuum system is much simpler and less expensive to produce AND TO REPAIR than an electrical system. And, at the time these cars were built, vacuum systems were more RELIABLE than electrical systems. With the advent of solid-state electronics, this is no longer the case. BUT, the C3 just has an electrical system of that vintage, so it really isn't better than vacuum systems of the day.

LEARN about the C3 vacuum system by purchasing a $10 booklet which provides detail on the design and how to [simply] diagnose any problems with it. If you had the same problem with an electrical system, you would spend significant time digging into the schematic and getting out your multimeter. For vacuum systems, you just need a vacuum gauge, some vacuum line, platic T-fittings/caps and some hand clamps. Once you understand this simple system and how it works, it's pretty easy to deal with.