C3 air conditioning troubleshooting?
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
The first troubleshooting tool you need is a manifold gauge set. With that you will be able to determine the cause or causes of the malfunction. Before buying the manifold gauge set, you will need to find out if it has been converted to r134A or if it still uses R12 refrigerant.
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
- Turn the A/C "on" and see if the compressor clutch engages and turns. If the clutch does not engage, the system is either low on freon, or you have an electrical problem preventing the clutch from being energized. Some year systems used a low pressure "fuse" in the engine compartment - this fuse would blow when the low side pressure got too low, preventing the compressor from engaging without freon in the system. If there is no power to the clutch, check this fuse (if equipped). If the fuse is blown, you have a freon leak that must be fixed prior to replacing the fuse.
- You can briefly depress one of the line schrader valves to see if there is freon pressure in the system. If there is no pressure, you likely have a leak. You can pressurize the system with shop air to find the leak and repair it (using soapy water at all connections and components to find the leak). Once the leak is found, the system will need to be thoroughly pumped down with a vacuum pump to remove all air and moisture from the system. You will need a gauge manifold set to pressurize the system and to evacuate it.
- If the compressor engages, the discharge line going from the compressor to the condenser should be hot. The line going from the condenser to the expansion valve (or orifice) should be very warm. All lines from the expansion valve (or orifice) back to the compressor should be very cold. Touch the lines to verify these conditions.
- If the lines at any point between the condenser and the expansion valve are cold, the component on the condenser-side of the line being cold has a restriction in it. It is very common for the receiver-drier to be partially plugged, and it will act as an expansion valve. Both sides of the receiver-drier should be the same temperature (very warm).
Lars
Last edited by lars; Jul 15, 2019 at 10:36 AM.
Advanced
Joined: Jun 2005
Posts: 62
Likes: 2
From: Jacksonville Florida
On my '77 that will soon be converted to 134a, Will I need to replace to condenser / dryer or both. I have a new compressor to install as well.
Thanks
Thanks
Last edited by Catnip; Jul 16, 2019 at 12:40 PM.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Advanced
Joined: Jun 2005
Posts: 62
Likes: 2
From: Jacksonville Florida
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Safety Car
Joined: Dec 2007
Posts: 4,229
Likes: 39
From: Beautiful East Texas
Has anyone considered or used this compressor upgrade kit as an option:
https://www.ebay.com/itm/73-77-CORVE...1/362486891072
The VIR seems to be a source of problems in this system, particularly when using R134 as the cooling agent.
Thoughts or comments appreciated.
mardyn
https://www.ebay.com/itm/73-77-CORVE...1/362486891072
The VIR seems to be a source of problems in this system, particularly when using R134 as the cooling agent.
Thoughts or comments appreciated.
mardyn
Last edited by mardyn; Jul 20, 2019 at 01:11 PM.
Advanced
Joined: Jun 2005
Posts: 62
Likes: 2
From: Jacksonville Florida
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Mind you that R134 is about 20-25% less efficient as well so if your system is not as cold.....that would be a big reason why....
Jebby