A/C Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Andy4639 · 04-20-2020, 09:06 AM

If you are wanting a 100% AC to work good then I would leave it. That ensures the hot water doesn't come into the cab while the AC is on. Most people put it in the other line though. If the vacuum operated valve leaks hot water by then your AC will never get as cold as it should inside the cab. Putting it in the other line makes sure it doesn't circulate at all through the heater core.
If you do decide to take it out a simple test is to feel the lower part of the interior heater box to see if it is warm when the AC is on and the truck is sitting still. If it is some what warm then you have water leaking by the vacuum valve and you will not get the cab as cool as it could be.

Davidf · 04-20-2020, 05:29 PM

Quote:

Originally Posted by Andy4639

If you are wanting a 100% AC to work good then I would leave it. That ensures the hot water doesn't come into the cab while the AC is on. Most people put it in the other line though. If the vacuum operated valve leaks hot water by then your AC will never get as cold as it should inside the cab. Putting it in the other line makes sure it doesn't circulate at all through the heater core.
If you do decide to take it out a simple test is to feel the lower part of the interior heater box to see if it is warm when the AC is on and the truck is sitting still. If it is some what warm then you have water leaking by the vacuum valve and you will not get the cab as cool as it could be.

Or to test: when the heat is off, the hose on one side (downstream side) of the factory valve should be cool.

**Already Gone** · 04-20-2020, 11:43 PM

I'm replacing my heater core pretty much as soon as truck is out of storage and plan to check everything in heater box etc. at same time.

04-20-2020, 09:06 AM	#1
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: A/C Question If you are wanting a 100% AC to work good then I would leave it. That ensures the hot water doesn't come into the cab while the AC is on. Most people put it in the other line though. If the vacuum operated valve leaks hot water by then your AC will never get as cold as it should inside the cab. Putting it in the other line makes sure it doesn't circulate at all through the heater core. If you do decide to take it out a simple test is to feel the lower part of the interior heater box to see if it is warm when the AC is on and the truck is sitting still. If it is some what warm then you have water leaking by the vacuum valve and you will not get the cab as cool as it could be. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

04-20-2020, 11:43 PM	#3
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,171	Re: A/C Question I'm replacing my heater core pretty much as soon as truck is out of storage and plan to check everything in heater box etc. at same time. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021



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