Heater core open with AC running - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HBlue · 07-07-2016, 06:01 AM

I'm working on a 76 Custom Deluxe. Part of the restoration was replacing the AC compressor that had blown. When I got it back, it just didn't seem to be putting out air as cold as I expected. I took part of the duct work off and found the lower right side of it was hot. My heater core shutoff valve must not be closing completely. I adjusted the shut off but that did not fix the problem.

I once had a 72 Bronco that shut off the incoming water with an inline valve. Can you still get those or is there another solution I'm missing.

**hatzie** · 07-07-2016, 09:35 AM

The blend door may not be closing completely.
Leaves or other debris in the heater box can block the blend door partway open. I pulled 3 key rings and a few different calibers of loaded rifle rounds out of my heater.
The hot-cold cable must be properly installed and adjusted as well.

07-07-2016, 06:01 AM	#1
HBlue Registered User Join Date: May 2014 Location: Louisiana Posts: 28	Heater core open with AC running I'm working on a 76 Custom Deluxe. Part of the restoration was replacing the AC compressor that had blown. When I got it back, it just didn't seem to be putting out air as cold as I expected. I took part of the duct work off and found the lower right side of it was hot. My heater core shutoff valve must not be closing completely. I adjusted the shut off but that did not fix the problem. I once had a 72 Bronco that shut off the incoming water with an inline valve. Can you still get those or is there another solution I'm missing.

07-07-2016, 09:35 AM	#2
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,915	Re: Heater core open with AC running The blend door may not be closing completely. Leaves or other debris in the heater box can block the blend door partway open. I pulled 3 key rings and a few different calibers of loaded rifle rounds out of my heater. The hot-cold cable must be properly installed and adjusted as well. __________________ 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.



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