73 No Heat?
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
73 No Heat?
Hi again 
Hey all
I cant seem to get any hot air out of the heater/defroster/vents ect: on my 73
I thought it was a problem with the thermostat at first because the temp gauge was barely climing above 100 degrees... So... I bought a new 195 degree thermostat and when I went to install it I found there was NO thermostat installed
Now it's running at 200 degrees but I can get no hot air.
I did find one vacuum control valve coming off the intake manifold but I think it's part of the air conditioning control.
One of the heater hoses is hot and the other is cool (dont recall which is which, it's late, the car is cooled down and im too tired to check
)
Is anybody familiar with this heating system so I can have a reference point to start at?
Im also experiencing a chatter from the rear when making either a left or right turn from a complete stop... but thats another topic....
Thanks in advance!!!
Hey all
I cant seem to get any hot air out of the heater/defroster/vents ect: on my 73
I thought it was a problem with the thermostat at first because the temp gauge was barely climing above 100 degrees... So... I bought a new 195 degree thermostat and when I went to install it I found there was NO thermostat installed
Now it's running at 200 degrees but I can get no hot air.
I did find one vacuum control valve coming off the intake manifold but I think it's part of the air conditioning control.
One of the heater hoses is hot and the other is cool (dont recall which is which, it's late, the car is cooled down and im too tired to check
)Is anybody familiar with this heating system so I can have a reference point to start at?
Im also experiencing a chatter from the rear when making either a left or right turn from a complete stop... but thats another topic....
Thanks in advance!!!
Racer
Joined: Dec 2003
Posts: 304
Likes: 0
From: Pasadena Maryland
I would think that the hot water shut off valve is stuck in the closed postion. I would check that out first before tackling the heater core. As far as your differential making noises try draining the rear end and put in some new gear oil along with a bottle of Limitied Slip Additive. Took me two changes to get mine to stop chattering.
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Easy enough...and unfortunate but true....if one heater hose is hot and the other is cold....the heater core is plugged....I'm sure you didn't want to hear that...sorry
UNLESS...on my car there is a vacuum controlled shutoff down by the passenger exhaust manifold..in line...if the hose is hot on the radiator side of that valve and cold on the other side...that would be the culprit...
UNLESS...on my car there is a vacuum controlled shutoff down by the passenger exhaust manifold..in line...if the hose is hot on the radiator side of that valve and cold on the other side...that would be the culprit...
Last edited by kb2fzq; Mar 23, 2006 at 08:51 AM.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by djgrelli
I would think that the hot water shut off valve is stuck in the closed postion. I would check that out first before tackling the heater core. As far as your differential making noises try draining the rear end and put in some new gear oil along with a bottle of Limitied Slip Additive. Took me two changes to get mine to stop chattering.
Also, the rear on my 72 is Positraction.
Could that be what's causing the chatter?
I dont know if limited slip and posi are one in the same
Thanks for the reply!
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by kb2fzq
Easy enough...and unfortunate but true....if one heater hose is hot and the other is cold....the heater core is plugged....I'm sure you didn't want to hear that...sorry
UNLESS...on my car there is a vacuum controlled shutoff down by the passenger exhaust manifold..in line...if the hose is hot on the radiator side of that valve and cold on the other side...that would be the culprit...
UNLESS...on my car there is a vacuum controlled shutoff down by the passenger exhaust manifold..in line...if the hose is hot on the radiator side of that valve and cold on the other side...that would be the culprit...
I will look for the shut off where you have suggested
Thanks
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
The hot water valve in in one heater hose right in front of where the hoses go into the firewall. It will be clear when you look for it. Follow both hoses from the pump and manifold to the firewall. It is either a Vacuum controlled valve, a Manual Valve installed by PO, or a mechanical valve controlled by a cable.
Trace it down and let us know
Trace it down and let us know
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Originally Posted by djgrelli
I would think that the hot water shut off valve is stuck in the closed postion.....
It's more likely to be the valve than the heater core.
Racer
Joined: Dec 2003
Posts: 304
Likes: 0
From: Pasadena Maryland
Limitited Slip is the correct term. Your clutch plates are gummed up. Do a good cleaning and add some LS Additive and it'll clear up. Mine drove me crazy. Thought the rear was going to fall off, especially after a long run.
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Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I think it is the heater control valve. If it was a vacuum door, you would still get hot air coming out some of the vents, just maybe not the right ones.
Also, I don't understand how it could be the heater core unless something was plugged up in it. Otherwise, it just acts as a hot device that air blows over. There is nothing else to it.
Also, I don't understand how it could be the heater core unless something was plugged up in it. Otherwise, it just acts as a hot device that air blows over. There is nothing else to it.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Hey!!!!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by djgrelli
Limitited Slip is the correct term. Your clutch plates are gummed up. Do a good cleaning and add some LS Additive and it'll clear up. Mine drove me crazy. Thought the rear was going to fall off, especially after a long run.
It does get worse after Ive been driving for a while... not as bad when the vehicle is cold.
I may start a new thread on the chatter issue just to get as much input as I can.
Maybe someday Ill be able to answer someone elses questions.
I swear, this car is clean and it has a ton of new parts but its Fix one thing and all of the sudden two other things need attention
After all... It is still just a 1973 Chevy
Thanks very much
Last edited by Bob Onit; Mar 23, 2006 at 07:10 PM.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by carl a
i just posted 2 posts for you on the vaccume controls for your car,,,WHERE HAVE YOU BEEN??????????
Safety Car
Joined: Jun 2002
Posts: 4,135
Likes: 1
no your not,,, go up to the search bar .click it,,when the drop box drops type heat,defrost,,,it will pull up the posts i made before on checking the vaccume system,,i cannot find the other one i did for you,,,sorry but my hands are so sore from wrenching it hurts typing and i just dont wanna type all that again!! if you get stumped on the vaccume e mail me and ill walk you thru it,,the accuators can be checked one by one by disconnecting the feed from the switch in your console and feeding them w/ vaccume from a temp line you can run from under the hood,,,,check the search i put a diagram there all color coded w/ the same color tracers as the car has,,,what the heck ill post the photo again,,,its real e z --------------------------------------------
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by Bob Onit
Hey!!!!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by Bob Onit
Hey!!!!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!
I located the problem
It was a vacuum valve located on the front of the intake manifold.
It works with the A/C... when you turn on the AC it is supposed to close the valve... it was stuck closed.
I removed the valve and just hooked up the heater hose direct and ...HEAT!
Ill have to get to a dealer and get a new valve.
As far as the chattering goes, I will try changing the rear diff fluid.
I need to know what kind of additive to get and how much I need and also how to add it... mix it with the gear oil, put it in first, last ect.
Once again .... you guys come through!