1978 AC Question
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From: Camden NY
St. Jude Donor '10
Kapsa and Basscat,
Thanks for the clarification and the picture. Ha ha, glad I didn't damage the AC thermostat! Or, maybe I did and don't know it yet.
I'll try your suggestions tomorrow and post the results.
Really appreciate ALL the advice here!
Bob
Thanks for the clarification and the picture. Ha ha, glad I didn't damage the AC thermostat! Or, maybe I did and don't know it yet.
I'll try your suggestions tomorrow and post the results.
Really appreciate ALL the advice here!
Bob
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From: Camden NY
St. Jude Donor '10
OK, jumped the wires on the comp switch, and the clutch engaged. Victory! Well, almost.
I hooked up the refrigerant can and added while the clutch was on. The problem was that it would be on for a minute or so then stop, then cycle again. But, it did suck up the refrigerant.
I then put the pressure gauge on the comp and it got confusing. When the clutch was stopped, the pressure reading showed 55 in the overcharged range. But when the clutch started again, the pressure reading dropped off to 24 in the undercharged range.
So, which is the accurate reading? When the clutch is engaged?
I never did get any cold air out of it. Is it possible I screwed up the thermostat when I jumped it the other day by mistake?
I hooked up the refrigerant can and added while the clutch was on. The problem was that it would be on for a minute or so then stop, then cycle again. But, it did suck up the refrigerant.
I then put the pressure gauge on the comp and it got confusing. When the clutch was stopped, the pressure reading showed 55 in the overcharged range. But when the clutch started again, the pressure reading dropped off to 24 in the undercharged range.
So, which is the accurate reading? When the clutch is engaged?
I never did get any cold air out of it. Is it possible I screwed up the thermostat when I jumped it the other day by mistake?
Racer
Joined: Dec 2007
Posts: 445
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From: Thomastown Mississippi
Great news. Compressor is working. It should be cycling on and off, especially if it's a little cool where you're at this morning. That means you're thermostat is working. Accurate reading would be when compressor clutch is engaged, so if it's reading 24, it's still a little low. Should be up around 40. One other thing, do you have a on/off valve in your heaters hoses. Most of us have installed them in these old cars. You can turn them off in the summer and it stops the hot water from going through the heater core inside the cabin. Makes a huge difference in how cold the air blows from the a/c. You can buy them at any hardware store and it takes ten minutes to install them, but they really do make a big difference in the amount of hot air reaching the cabin. I would add another can of refrigirant, bring it up to 40 psi, install the on/off valves, and you should have pretty cool air blowing inside. Keep us posted.
kc
kc
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From: Camden NY
St. Jude Donor '10
Great news. Compressor is working. It should be cycling on and off, especially if it's a little cool where you're at this morning. That means you're thermostat is working. Accurate reading would be when compressor clutch is engaged, so if it's reading 24, it's still a little low. Should be up around 40. One other thing, do you have a on/off valve in your heaters hoses. Most of us have installed them in these old cars. You can turn them off in the summer and it stops the hot water from going through the heater core inside the cabin. Makes a huge difference in how cold the air blows from the a/c. You can buy them at any hardware store and it takes ten minutes to install them, but they really do make a big difference in the amount of hot air reaching the cabin. I would add another can of refrigirant, bring it up to 40 psi, install the on/off valves, and you should have pretty cool air blowing inside. Keep us posted.
kc
kc
Also, re your comment on the ambient air temp, it was 60 this morning when checking the AC cabin air.
I'll add more refrigerant later today and bring it back up to the 35-40 range.
Where are those on/off heater valves located? On the firewall before going into the heater core? Is it a matter of slicing the heater hose and adding the valve in between?
After reading about the heat in the cabin on other threads, all of them mentioned the heat coming up through the floorboards and not the heater core. Makes a lot of sense and I plan on doing the valves if not already installed.
Thanks again, Kenny. I can cancel the appointment on Monday with the mechanic.
Racer
Joined: Dec 2007
Posts: 445
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From: Thomastown Mississippi
Yes, to install the coolant shut off valves, you just cut the heater hoses in half and install the on/off valves with clamps. If you have a NAPA parts house nearby, they should have them. Some people will say you only need to do one heater hose. Some say both. I installed the on/off valve on both hoses, and it really does make a big difference in the hot air reaching the cabin. The two heater hoses are two different size diameter. I think one is 5/8 inch inside diameter, and the other is maybe 7/8. Just so you know when you go to buy them. Just cut the heater hoses in half where ever it is most convenient and easiest for you to reach to install the valves. Both heater hoses should be on the passenger side. Let us know how you make out.
Kenny
Kenny
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From: Camden NY
St. Jude Donor '10
FWIW, and for those like me that are not mechanics, here are the Autozone manual shutoff valves for the heater hoses:
3/4" valve:
5/8" valve:
A guy on another board mentioned he installed these with 1" screw clamps underneath the car just before the hoses bend up to the heater core.
I'll post some pics and my installation steps when I do this.
3/4" valve:
5/8" valve:
A guy on another board mentioned he installed these with 1" screw clamps underneath the car just before the hoses bend up to the heater core.
I'll post some pics and my installation steps when I do this.
Race Director
Joined: May 2006
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From: Dayton, Ohio
FWIW, and for those like me that are not mechanics, here are the Autozone manual shutoff valves for the heater hoses:
3/4" valve:
5/8" valve:
A guy on another board mentioned he installed these with 1" screw clamps underneath the car just before the hoses bend up to the heater core.
I'll post some pics and my installation steps when I do this.
3/4" valve:
5/8" valve:
A guy on another board mentioned he installed these with 1" screw clamps underneath the car just before the hoses bend up to the heater core.
I'll post some pics and my installation steps when I do this.
(I personally prefer a much simpler and safer set of pinch pliers designed to stop coolant flow if your not going to use the factory coolant shut off valve.)
Safety Car
Joined: Jun 2004
Posts: 4,371
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From: Beecher Illinois
In YOUR post no 16 in the top pic you can see the factory vacuum shutoff valve.
Put your manual valve there.
I like the vacuum valves but you gotta make sure they work.
One of mine didn't work for 25 years rendering the AC pretty useless. Last spring I fornd that the manual linkage was not activating the vac switch behind the glovebox. A slight adjustment and ice cold air!
Put your manual valve there.
I like the vacuum valves but you gotta make sure they work.
One of mine didn't work for 25 years rendering the AC pretty useless. Last spring I fornd that the manual linkage was not activating the vac switch behind the glovebox. A slight adjustment and ice cold air!
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Safety Car
Joined: Jun 2004
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From: Beecher Illinois
Replaced it with a ball valve from the hardware store.
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Instructor
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From: Camden NY
St. Jude Donor '10
In YOUR post no 16 in the top pic you can see the factory vacuum shutoff valve.
Put your manual valve there.
I like the vacuum valves but you gotta make sure they work.
One of mine didn't work for 25 years rendering the AC pretty useless. Last spring I fornd that the manual linkage was not activating the vac switch behind the glovebox. A slight adjustment and ice cold air!
Put your manual valve there.
I like the vacuum valves but you gotta make sure they work.
One of mine didn't work for 25 years rendering the AC pretty useless. Last spring I fornd that the manual linkage was not activating the vac switch behind the glovebox. A slight adjustment and ice cold air!
Thanks again.
Bob
Race Director
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From: Dayton, Ohio
Safety Car
Joined: Jun 2004
Posts: 4,371
Likes: 223
From: Beecher Illinois
I'm suggesting replacing the vacuum valve with the manual valve unless you're sure the vacuum valve works.
I found the problem with mine when the hose started leaking at the valve. Wasn't sure if vacuum opened or closed the valve so with it off the car I hooked it up to a vacuum source on another car and blew through it with the car running and with it not running. Couldn't blow through it with the car running, so, vacuum closed it.
Checked the vacuum line on the Vette the valve went on and it never closed the valve.
Pulled the glove box out, and on the heater case was the switch and cable lever. Not enough arc in the lever. Simply put a small plastic cap I had on the switch plunger and all was good again! Probably first time it ever worked.
I remember having the AC system charged back in the 80s. Guy claimed it was right there on freon but still blew warm air out the vents.
Good clue to the vacuum valve not closing. When you first start the Vette, if you get nice cold air and it gradually gets warm, probably valve not shutting.
Air blows cold while the anti freeze is cold, as the anti freeze warms up, so does the AC.
Racer
Joined: Dec 2007
Posts: 445
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From: Thomastown Mississippi
I've got those valves pictured installed on my car. They can be stiff to turn and the hex part can back out on occasion, but I found the trick to that is to let the car warm up, then open or close them and they work ok. Once the coolant and engine are warm, they seem to move freely. The ball valves are probably smoother, but whatever you install, you're not going to be opening and closing it very often. I usually open and close mine once or twice a year but I could probably leave them closed all the time, as we have pretty mild winters and these cars seem to hold heat pretty good, to say the least. When you get it all together and try the air, let us know how it does. One more thing while you're in there. I can't tell from looking at your pictures, but the sensor coming off of the a/c thermostat that attaches to the a/c line should be wrapped in insulation to work properly. Take a look while you're in there and see. NAPA sells that wrap insulation.
Kenny
Kenny
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From: Camden NY
St. Jude Donor '10
KapsSA & Kenny,
More good stuff to add to my knowledge base and also for other folks checking the thread.
I'll try to find ball valves, but will also check that vacuum valve.
Thanks guys and have a good weekend.
PS: winters here are below freezing with about 10-12 feet of snow on average, with 20+ feet every couple of years. With that said, I won't be driving the Vette once the snow flies until maybe March. The salt is what concerns me more than some snow.
More good stuff to add to my knowledge base and also for other folks checking the thread.
I'll try to find ball valves, but will also check that vacuum valve.
Thanks guys and have a good weekend.
PS: winters here are below freezing with about 10-12 feet of snow on average, with 20+ feet every couple of years. With that said, I won't be driving the Vette once the snow flies until maybe March. The salt is what concerns me more than some snow.
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From: Camden NY
St. Jude Donor '10
I started her up this AM and put the AC on Max. The clutch engaged, so I put more refrigerant in when the clutch was on until the new can was empty.
Then pulled the car out of the garage into the warm, sticky ambient air and put the AC cabin fan on high. I had cold air coming into the cabin.
So, this all may have been just a matter of me knowing that the clutch has to be on in order to add refrigerant.
Next step is to shut off the antifreeze circulation into the heater.
Thanks to all who helped me on this!
Bob
Then pulled the car out of the garage into the warm, sticky ambient air and put the AC cabin fan on high. I had cold air coming into the cabin.
So, this all may have been just a matter of me knowing that the clutch has to be on in order to add refrigerant.
Next step is to shut off the antifreeze circulation into the heater.
Thanks to all who helped me on this!
Bob
Racer
Joined: Dec 2007
Posts: 445
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From: Thomastown Mississippi
That's great, glad you got it going. Summers up there probably aren't as brutal as they are down here in the south. The factory air set-up should work well for you. Don't forget to make sure that the thermostat sensor that is wrapped around the a/c line is wrapped in insulation. That is what makes your compressor cycle on and off so that the lines and accumulator don't freeze up. Mine only cycles on and off when it's kinda cool outside, upper 60's/lower 70's. If I drive in the heat of the day, 90 degrees or above, compressor runs pretty constant. Glad you got it fixed. Makes driving a lot more fun.
Kenny
Kenny
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From: Camden NY
St. Jude Donor '10
Be careful with these valves,the hex part sometimes backs out when opening the valve for heat and sends hot coolant spraying everywhere.
(I personally prefer a much simpler and safer set of pinch pliers designed to stop coolant flow if your not going to use the factory coolant shut off valve.)
(I personally prefer a much simpler and safer set of pinch pliers designed to stop coolant flow if your not going to use the factory coolant shut off valve.)
I thought pinch pliers would only be used for a very short period of pinching off the hoses when working on the coolant system. If you leave them on all summer, do they cause any damage to the hoses?
And they stay on during all the normal road bumps, etc? I like your suggestion better but wondered about long-term use.
Bob
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From: Dayton, Ohio
Roger,
I thought pinch pliers would only be used for a very short period of pinching off the hoses when working on the coolant system. If you leave them on all summer, do they cause any damage to the hoses?
And they stay on during all the normal road bumps, etc? I like your suggestion better but wondered about long-term use.
Bob
I thought pinch pliers would only be used for a very short period of pinching off the hoses when working on the coolant system. If you leave them on all summer, do they cause any damage to the hoses?
And they stay on during all the normal road bumps, etc? I like your suggestion better but wondered about long-term use.
Bob
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From: Camden NY
St. Jude Donor '10
[QUOTE=...Roger...;1574388130]I've been seeing more and more of the pinch pliers. I haven't noticed any damage to the hoses other than a dent in the rubber that seems to disappear shortly after the pliers are removed. The guy that owns this car says he leaves the pliers on only while driving. They are very light plastic so I doubt bouncing will be an issue unlike a set of heavy vicegrips. The one in this pic is from Harbor Freight and come in a 3 pack for 12.99. I have some from HF and I also have some more expensive ones. HF also has some other clamps that go all the way around the hose and could never fall off but they're metal.
Thanks for the info. Just got one from NAPA.
Bob
Thanks for the info. Just got one from NAPA.
Bob