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**hatzie** · 04-13-2022, 08:02 PM

The digital heat/AC controller gets cabin temp from a sensor in the headliner over the driver's head. It has a little fan inside IIRC.
It looks kinda like a microphone grille.

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Name: HVAC Air Temp.jpg
Views: 57
Size: 12.9 KB

There's also a sun load sensor dead centre between the defrost vents on the dash that does double duty as a nighttime sensor to turn on the auto headlights.

If both of those sensors are working properly and the ambient outside temp sensor is reporting the correct temp in your mirror then the HVAC controller may be flaking out on you.

You should be able to get a look at the reported temperatures with an Snap On Verus, AUTEL Maxsys, or Tech2.

04-13-2022, 08:02 PM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,919	Re: Cabin temp regulation The digital heat/AC controller gets cabin temp from a sensor in the headliner over the driver's head. It has a little fan inside IIRC. It looks kinda like a microphone grille. There's also a sun load sensor dead centre between the defrost vents on the dash that does double duty as a nighttime sensor to turn on the auto headlights. If both of those sensors are working properly and the ambient outside temp sensor is reporting the correct temp in your mirror then the HVAC controller may be flaking out on you. You should be able to get a look at the reported temperatures with an Snap On Verus, AUTEL Maxsys, or Tech2. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 04-13-2022 at 08:10 PM.