New 1976 Owner with Limited Skills

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Group - I just bought my first Corvette -1976. I have no experience with working on cars at all, but am a fast learner. I drove it home last night and found out that the heat doesn't work. I'm not sure
where to begin to search for the problem. Is this something that I can fix myself or should I take it to a mechanic?
For diagnostic purposes - the fan blower works and both dials on the control panel move and air flows both at the top and bottom. I put it on defrost, heater, and vent and had the same frigid results.
Any help will be appreciated...
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what about the temp slide bar ? Does it work ? are you sure that the heater core has NOT been bypassed ?
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'Key
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The temp slider does move, but I don't know if it's doing anything. Is there an easy way for me to tell if it's actually moving the proper door?
As far as the heater core being bypassed...I have no idea and don't really even know what that means, so any enlightenment would be helpfull!!!!
Thanks
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'Key
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"1976VetteGuy" < snipped-for-privacy@gmail.com> wrote in message
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Here's some diagrams that might help you understand what's in your car: http://www.docrebuild.com/dr-r-web/AC-VAC2.PDF
Look at the diagram at the bottom center of the page and note the unlabeled device at the top of the picture... that's a metal diverter valve that sits in the engine compartment and has heater hoses connected to it. The heater hoses are attached to the nipples shown at the top and right coming out of that valve, the small hose shown as white in the diagram is a vacuum hose that actuates the diverter valve to send hot water through to the heater core under the dash when you turn on the heater, or to bypass the heater core and send the hot water back to the engine.
note: This particular picture shows a system without a/c, but I believe that same valve is present on cars that DO have a/c as well, but they just don't show it on the a/c diagram (upper left on the page), they only show the airflow door actuators. I don't have a C3, so I can't verify that.
That valve can stick or become disconnected from the vacuum hose, or there could be a leak in the vacuum system that prevents sufficient vacuum from reaching the valve. It is a common point of failure. The valve is not particularly expensive to replace.
It could be checked by applying vacuum directly to the valve to see if the heater then works (you should be able to feel that the water hose from the diverter to the heater is cool before vacuum is applied, then heats up with vacuum applied). You may need a vacuum pump to test with, or you can "borrow" vacuum from another vacuum source on the engine by "Tee"ing into that good vacuum source. (Simply sucking on the hose orally is not likely to produce sufficient vacuum.)
You could also disconnect the two water hoses from the diverter valve and clamp them to opposite ends of one short section of copper tubing (5/8" I believe) to bypass the valve for the winter, then reattach them to the diverter valve in the spring.
Good luck.
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Well, I may have lied a bit...after some reflection, I think what I called the "diverter" valve simply stops water from passing through to the heater, rather than diverting it back to the engine.
WayneC wrote:

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wow...thanks for the detailed answer. I'll check that out tonight when I get home...
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To all that helped me out I thank you...
So from reading past posts, I am going to install the manual valves on the hoses as I think the vacuum control valve might be stuck in the closed position or something as I am not getting any flow to the heater core.
One last question to everyone about this...do I need to drain the coolant level down to close off these valves in the summer? Also, when they are shut off, how can I make sure the heater core is not going to rust while it is not being used? In other words, do I drain it somehow when I close off the manual valves? Or does the water just stay in there all summer?
Thanks again!!!
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you should get the flow going to the heater core first. then don't drain the core. just simply open the valves from time to time to circulate the coolant through the heater core.
g'day
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So I replaced the vacuum valve with a manual one and now I have heat. The old valve was all gunked up and plugged, so I thank everyone that helped me!
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1976VetteGuy wrote:

Did you price a vacuum valve? I think they are pretty reasonably priced. Why be fiddling with a valve under the hood when you don't have to? The heater core is made of aluminum (or possibly copper)... assuming that you keep a 50/50 mixture of water and quality anti-freeze in your cooling system and drain/refill every 3 to 5 years, with no leakage in the system in between refills, then no "rusting" or other deterioration should occur (it's just like leaving Pepsi in the can), so no need to drain the heater core.
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I did look at a new vacuum valve, but it's not price that made me go with the manual valves. The original valve didn't have any vacuum line hooked up to it and I couldn't find one that wasn't being used, so I would have had to fix the vacuum problem and I just wanted to get the heat working. Besides that, most of the forums that I have read, say that the manual valves are better in the hotter days because it cuts off the supply of hot water to the heater core and makes the interior cabin much cooler. I know it's not stock or original, but I can always go back to that if I want or need to do so.
Thanks for the reply!!!
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Thanks...I don't think it was bypassed, but not sure. I actually don't even know where the heater core is located...I assume it's behind the firewall??? So if you have the time, can you get more detailed and tell me how to check this as I have replaced the thermostat and made sure it has enough coolant. I'm pretty sure it either a hose or heater core problem of some sort. I wouldn't know what the bypass would look like. I can't even find the damn water pump. I bout a new one, but my future father-in-law says that I would know if it was bad as it would be noisy and the car would overheat. So I need to find that so I can follow the hoses to the heater core? The guy at Autozone said that I should try to clean/flush out the cooling system...to try to clean out any gunk or rust that may be in there???? I bought a kit and a solvent to flush it with, but don't want to go throughg the trouble if I don't have to....???? It would be a cheap fix if it worked...
Is the heater core hard to get to???
Thanks for your help...
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The other possible solutions are much easier to try. I've done the heater coil, A/C, and pretty much everything else on my 1982. The heater coil fits through the firewall. The first step in the repair manual is to remove the seats, dash, and everything over the interior part of the heater coil. The second step involves removing the parts in the way under the hood. A good mechanic will charge about $500-700 for the day it will take to replace it. Start by finding a repair manual for your 1976.
David
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I bought the C3 (it says like 1966-1976 Shop Manual in red on the cover) Shop Manual, but am very disappointed in the content. What are the best shop manuals out there?
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I have both the 1982 Shop Manual and Chilton's. They do leave much to be desired. My mechanic subscribes to the Mitchell Repair Manuals as well as many others. Perhaps Mitchell has a limited distribution you could buy. I'd suggest finding a local mechanic (Master Auto Technician) and asking him/her. They will likely help describe the process or let you look at manuals. My mechanic would let you do it yourself, off hours, with his tools for a pittance.
David
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wrote:

my local library subscribes to the mitchell database. one can use it for free at the library.
regards, charlie cave creek, az
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On Wed, 5 Dec 2007 17:19:24 -0800 (PST), 1976VetteGuy

The GM shop manual is the only manual I've ever found that worth buying. The others skip to much material or leave key steps and areas "unexplained".. ----------- Elbert snipped-for-privacy@me.com
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Where can I get the GM shop manual?
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On Thu, 6 Dec 2007 17:26:06 -0800 (PST), 1976VetteGuy

http://www.helminc.com
They are relatively expensive but it you have a car you plan to keep and would like to learn about the car or do the work yourself. The GM shop manuals are the best. A 76 corvette would be for the most part basic stuff, but everyone has to start somewhere. A GM shop manual is a good investment. You might hunt around E-Bay too. I would not waste my money on a CHILTON or Haynes unless that's the only thing you can get. ----------- Elbert snipped-for-privacy@me.com
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