Defrost and Air Conditioning [message #337964] |
Wed, 17 October 2018 21:49  |
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SteveW
 Messages: 538 Registered: June 2005 Location: Southern California - Ora...
Karma: 1
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Greetings !!
We had a lively discussion at work today - about air conditioning engaging when one selects defrost on automotive HVAC systems. Dehumidifying the air being the main objective.
I agreed that "modern" cars do so and took a position that the vehicles from the 70s don't.
Might any of y'all know the specifics of when this started ?? Does it work as such in our coaches ??
There's no betting money in the mix - but I'd sure like to be correct.
Thanks in advance,
Steve W
1973 23'
Southern California
Steve W
1973 : 23'
Southern California
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Re: Defrost and Air Conditioning [message #337996 is a reply to message #337964] |
Fri, 19 October 2018 08:27   |
JohnL455
 Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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It started mid 70s some time on GM. They added the ECONOMY script above the VENT and HEAT selections to show that the compressor would not run in only those two positions. All other posItions ran compressor above a sub freezing OAT
John Lebetski
Woodstock, IL
77 Eleganza II
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Re: Defrost and Air Conditioning [message #338013 is a reply to message #337964] |
Sat, 20 October 2018 08:34  |
JohnL455
 Messages: 4447 Registered: October 2006 Location: Woodstock, IL
Karma: 12
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Senior Member |
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Let me qualify my statement and augment. If you opted for GM Comfotron Auto climate control the compressor ran (except below freezing). The system then blended hot and cold to achieve the desired cabin temp. My grandfather had a 67 Olds 98 LS and that was how it worked. So this preceded the manual AC running compressor on DEF by at least a decade.
John Lebetski
Woodstock, IL
77 Eleganza II
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