77 AC help needed
Thread Starter
Racer
Joined: Feb 2008
Posts: 357
Likes: 3
From: Madisonville Kentucky
77 AC help needed
Hi guys,
I am having trouble with my AC not blowing cold in my 77. The compressor runs and stays on, and the pipe on the output side of my compressor gets extremely cold (to the point where it ices up with frost). However, the air coming out of the vents, even on max AC is ambient temperature at best. I thought that maybe my heater core valve was not working properly but I tested it by checking the vaccum with a vac gauge, and to double check I shut off the flow of coolant by clamping on a pair of vice grips on the coolant line running to the valve. Any ideas on what the problem could be? Is it possible that although my compressor kicks on and runs that the freon could be low causing the problems?
Thanks
I am having trouble with my AC not blowing cold in my 77. The compressor runs and stays on, and the pipe on the output side of my compressor gets extremely cold (to the point where it ices up with frost). However, the air coming out of the vents, even on max AC is ambient temperature at best. I thought that maybe my heater core valve was not working properly but I tested it by checking the vaccum with a vac gauge, and to double check I shut off the flow of coolant by clamping on a pair of vice grips on the coolant line running to the valve. Any ideas on what the problem could be? Is it possible that although my compressor kicks on and runs that the freon could be low causing the problems?
Thanks
Melting Slicks
Joined: Sep 2011
Posts: 3,372
Likes: 215
From: Peoria Arizona
My first guess would be in your vent system. Sounds like your diverter door is not working correctly. Also possible that your outside air valve is not functioning properly. That's the system that controls the "door" behind the passenger side kick panel which allows outside air in.
I have not tackled the AC system in our '77 yet and am not very knowledgeable of the system at this point. Hopefully someone can correct or confirm what I said here.
Adam
I have not tackled the AC system in our '77 yet and am not very knowledgeable of the system at this point. Hopefully someone can correct or confirm what I said here.
Adam
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
My first guess would be in your vent system. Sounds like your diverter door is not working correctly. Also possible that your outside air valve is not functioning properly. That's the system that controls the "door" behind the passenger side kick panel which allows outside air in.
I have not tackled the AC system in our '77 yet and am not very knowledgeable of the system at this point. Hopefully someone can correct or confirm what I said here.
Adam
I have not tackled the AC system in our '77 yet and am not very knowledgeable of the system at this point. Hopefully someone can correct or confirm what I said here.
Adam
You can see inside the air box by taking off that resister block on top of the box, two screws. Can look in there while the temp lever is moved and see if the blend door is working. Also can see if it is full of a mouse house or leaves or something blocking air.
Thread Starter
Racer
Joined: Feb 2008
Posts: 357
Likes: 3
From: Madisonville Kentucky
minitech, can you advise more specifically where the resistor block is that you are referring too? Is it the one under the hood on the passenger side of the vehicle? Or inside vehicle?
thanks for your help guys
Instructor
Joined: Apr 2011
Posts: 186
Likes: 2
From: Moncks Corner SC
Bob
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
Can anyone post a pic showing it?
Thread Starter
Racer
Joined: Feb 2008
Posts: 357
Likes: 3
From: Madisonville Kentucky
I added freon last summer, but none recently. I located the cover on the blower box and removed the two screws. The flapper/door seems to be functioning properly when I move the lever in the car from hot to cold. Also, it looks very clean in the box around the cores. Still scratching my head trying to determine what my problem is.
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Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
The aluminum and rubber line that comes from the evaporator box into the compressor is called the suction line. It should be cold and sweat but not frost. Low air flow through the evaporator will cause this. Look for blocked blower wheel or stopped up evaporator. You can see into the blower wheel housing without pulling the blower motor. Remove the plastic grill at the base of the windshield at the pass. fender upper edge. Sounds more like the evap. is dirty or blocked. mike...
Thread Starter
Racer
Joined: Feb 2008
Posts: 357
Likes: 3
From: Madisonville Kentucky
The aluminum and rubber line that comes from the evaporator box into the compressor is called the suction line. It should be cold and sweat but not frost. Low air flow through the evaporator will cause this. Look for blocked blower wheel or stopped up evaporator. You can see into the blower wheel housing without pulling the blower motor. Remove the plastic grill at the base of the windshield at the pass. fender upper edge. Sounds more like the evap. is dirty or blocked. mike...
Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
I have never seen that. The smaller line that goes to the condenser in front of the radiator is called the hot gas line. This is the discharge line from the compressor. If it is freezing then I am totally lost. Not the first time however. Plastic grill is inside the windshield wiper well. Pass. side. Along fender to hood edge. mike...
Thread Starter
Racer
Joined: Feb 2008
Posts: 357
Likes: 3
From: Madisonville Kentucky
I have never seen that. The smaller line that goes to the condenser in front of the radiator is called the hot gas line. This is the discharge line from the compressor. If it is freezing then I am totally lost. Not the first time however. Plastic grill is inside the windshield wiper well. Pass. side. Along fender to hood edge. mike...
Melting Slicks
Joined: Mar 2009
Posts: 3,126
Likes: 15
Ok. That is the suction line or the inlet to the compressor. I promise.
The hot line is indeed the outlet. Low refrigerant charge, inadequate air flow or partially blocked metering device (orifice tube) will cause the suction line to frost. mike...
The hot line is indeed the outlet. Low refrigerant charge, inadequate air flow or partially blocked metering device (orifice tube) will cause the suction line to frost. mike...