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Registered
2001 DTS
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33 Posts
Discussion Starter #1
Hey guys, I'm trying to figure out the HVAC system's quirks.

I run the A/C almost constantly, and sometimes, the wind noise and airflow seem like it's recirculating, even when I haven't explicitly turned recirculate on (Both fan speed and vents are user control, I don't like Auto). I always keep the temp control at 60 (the lowest setting). Will the system automatically turn on recirculate if, say, the difference between the temp control and "outside temp" is too high?

Also, the Auto HVAC control doesn't seem to do anything useful in the midrange. It blows cold from 60-64, then the entire range of 65-83 seems the same lukewarm temp with the fan running on low, and 84 and up start to get warmer, blowing full hot at 90. Is this the normal operation?

Last, the vents are spitting out this dark brown foam that seems to be saturated with oil. Is that the sealing foam used on the doors and such disintegrating?

Thanks.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,999 Posts
I always keep the temp control at 60 (the lowest setting).
setting the temp to either 60 or 90 over rides ALL the settings -

the recirculate door is closed -
the heater door is fully closed - cold - or fully open - hot -

if the AC system was working properly -
you would need to wear a winter parka inside the car -

when set to 60 - medium speed blower -
"perfect" air temp from the center vents -
is between 37 and 42* -

Will the system automatically turn on recirculate if,
say, the difference between the temp control and "outside temp" is too high?

no - not when set to 60 -
however -
if the evaporator gets too cold - or freezes up -
or if the liquid freon gets too cold -
the compressor will shut off -
so you would feel warmer air from the vents -
until the compressor fires up again -

-----------------------

if you can leave the temp set to 60 -
and NOT get frozen out -
your AC is not working correctly -

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Last, the vents are spitting out this dark brown foam
that seems to be saturated with oil.
Is that the sealing foam used on the doors and such disintegrating

YES -
and that means the various doors don't close tightly -
and could allow outside air past the recirculate door -
 

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Registered
2001 DTS
Joined
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33 Posts
Discussion Starter #3
Thanks, bc. I do like the cold a bit too much :).

I'll get my trusty IR thermometer and measure the vent temps at 60 w/medium fan speed.

In the meanwhile, this is what I noticed today while driving:

Constant condition: A/C on. Fan speed (5 bars, max) and vent control (face and floor) both user controlled, not auto.

Outside temp reading: 78 (variable).

If I turn off recirculate with the temp at 60, then raise the temp to within 4 degrees of the "outside" reading, recirculate turns off and stays off, even if I knob it back to 60. However, if I turn recirc on now (at 60 again), it will not turn off, which matches up with what you said about setting it to 60 overriding all the settings. Does the 4-degree thing sound like it's operating correctly?

What should I do about replacing the disintegrating foam? I'll check the box the cabin air filter goes in, too, since the foam bits are saturated with and smell like oil.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,999 Posts
What should I do about replacing the disintegrating foam?
the entire car is built around the AC "stack" -
unless you feel like disassembling the entire dash assembly -
turn the fan speed down - less foam will blow off -
and live with it -
 
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