Miata Mailing List: August 1998, Message #138

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Previously on Hot and Cool, Tim Hayes <hayes@vm.cc.latech.edu> said...

> I have noticed that after the engine warms up, fresh air coming through
> the vents is always warmer than the actual outside air.  Even on
> relatively cool nights (75 degrees - brrrr! sweater weather) fresh air
> or recirculated air is always warmer (uncomfortably warmer) than the
> actual outside air.  I long for fresh, cool outside air and the only way
> I can get it is to stick my head out the window.
> What's the deal?  Is this normal?

The HVAC selector box has a "feature" which prevents the diverter door from
achieving full travel.  Most often, it doesn't completely close off the heat,
resulting in what you describe.  It can be adjusted to close completely, at expense
of slightly less heating capability in the winter.

> At a red light (after the car
> has warmed up) the AC air is only slightly cooler than the outside air.
> Once moving the AC air is nice and cold.  The electric radiator fan, by
> itself, doesn't pull enough air through the condenser coils.
> What's the deal?  Is this normal?

The problem isn't airflow, it's freon flow.  The idling engine doesn't pump enough
freon to keep things cool.  Revving the engine will provide cooler air, but it's not
really practical.

> One final problem concerning the Miata AC.  I have discovered that I
> have two choices in my Miata in the summertime.  I can be either: Hot
> and quick or Cool and slow!  Lately, unfortunately, it's been cool and
> slow.  Do all 90 Miatas suffer with the AC on like mine does?    
> What's the deal?  Is this normal?

Small engine + big load from the compressor = poor performance.  They're all like
that.

	-John

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John Freas (jfreas@earthlink.net)
Red '90 Base-ish #7690
Birmingham, AL
Team LS1, SP, the Gap...
Team dlralt, PBC, Roebuck, Voodoo...
"I have no idea what those dimple things on the windshield frame are for."
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