I have a 73 GMC with the type of air conditioning that lets in outside
air even when in the recirculation mode. When in the recirculation mode,
with AC "on", a pneumatic valve closes off most of the outside air, but
there is still a significant opening. The manual says it would be 20%
outside air but I suspect its more than that.
To maximize the AC capacity I made a small sheetmetal flap that covers
the opening. Just a few cracks left at the sides.There is still a large
outside air opening when not in the recirculation mode.I intend to check
the AC discharge temp. both with and without the flap as soon as we have
some hot weather. This should have the maximum effect when setting at
idle with engine heat coming back into the air inlet.
Does anyone see a problem with this? I suspect the designers wanted the
outside air to maintain a slight positive pres. in the cabin to exclude
possible entrance of carbon monoxide. Maybe I should get a CO analyser
if thats a real problem. Recently I blew air into my coach with two yard
blowers and a small vacuum cleaner trying to get enough positive
pressure to check for roof leaks with a soap solution. My coach was so
ventillated, even with all the exterrior vents taped closed, that I
could barely blow a bubble. I concluded as Jim Bounds suggested that I
needed a bigger blower to do this effectively. But I also concluded that
the little outside air that wants to try to pressurize the cabin during
AC recirculation would probably be insignificant.
air even when in the recirculation mode. When in the recirculation mode,
with AC "on", a pneumatic valve closes off most of the outside air, but
there is still a significant opening. The manual says it would be 20%
outside air but I suspect its more than that.
To maximize the AC capacity I made a small sheetmetal flap that covers
the opening. Just a few cracks left at the sides.There is still a large
outside air opening when not in the recirculation mode.I intend to check
the AC discharge temp. both with and without the flap as soon as we have
some hot weather. This should have the maximum effect when setting at
idle with engine heat coming back into the air inlet.
Does anyone see a problem with this? I suspect the designers wanted the
outside air to maintain a slight positive pres. in the cabin to exclude
possible entrance of carbon monoxide. Maybe I should get a CO analyser
if thats a real problem. Recently I blew air into my coach with two yard
blowers and a small vacuum cleaner trying to get enough positive
pressure to check for roof leaks with a soap solution. My coach was so
ventillated, even with all the exterrior vents taped closed, that I
could barely blow a bubble. I concluded as Jim Bounds suggested that I
needed a bigger blower to do this effectively. But I also concluded that
the little outside air that wants to try to pressurize the cabin during
AC recirculation would probably be insignificant.
