Heat blowing while driving my '71 LS5
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,062
Likes: 266
From: Slower than a speeding bullet................ Fort Lauderdale, FL
Heat blowing while driving my '71 LS5
Recently bought the car.
While driving today, with outside temp just under 80, the heat was blowing from vents in front of console, getting the car uncomfortably warm.
I am trying to remedy the situation by stuffing towels into the vents to prevent the air from entering cabin.
Is this a good or bad idea? Just wondering about any back-pressure with the vents blocked up. Some air can still escape, as it's not an airtight fit.
Can't believe there is no way to turn off the fan that keeps blowing the air in. Or is there? I don't need any heat here even in winter, so am open to suggestions
on disabling heating system (block water heater hose?).
Thanks for any ideas.
While driving today, with outside temp just under 80, the heat was blowing from vents in front of console, getting the car uncomfortably warm.
I am trying to remedy the situation by stuffing towels into the vents to prevent the air from entering cabin.
Is this a good or bad idea? Just wondering about any back-pressure with the vents blocked up. Some air can still escape, as it's not an airtight fit.
Can't believe there is no way to turn off the fan that keeps blowing the air in. Or is there? I don't need any heat here even in winter, so am open to suggestions
on disabling heating system (block water heater hose?).
Thanks for any ideas.
Last edited by Mr. Wonderful; Feb 20, 2017 at 09:09 PM.
Intermediate
Joined: Nov 2006
Posts: 44
Likes: 0
The temp is controlled by a cable which opens and closes a door on the heater box. If you move the temp control from hot to cold, you should hear the door open and close. My guess is that the door is either stuck on heat or the cable broke.
I don't see why you couldn't pull the fan motor fuse. Unfortunately, you may lose other functions.
Just my two cents.
I don't see why you couldn't pull the fan motor fuse. Unfortunately, you may lose other functions.
Just my two cents.
Team Owner
Joined: Sep 2006
Posts: 31,289
Likes: 4,380
From: Westminster Maryland
Hi MRW,
Do you have an Owner's Manual for your car? It explains the operation of the heater/defroster or a/c controls for your car.
You don't mention if your car has a/c or not.
Since you mention "vents in front of console" I'm thinking a/c?
On non a/c cars the blower motor runs at 'Low' all the time, there's no 'Off' position.
On a/c cars there's a vacuum operated hot water shut off valve. Do you have the a/c controls set so the valve has been closed?
Regards,
Alan
Do you have an Owner's Manual for your car? It explains the operation of the heater/defroster or a/c controls for your car.
You don't mention if your car has a/c or not.
Since you mention "vents in front of console" I'm thinking a/c?
On non a/c cars the blower motor runs at 'Low' all the time, there's no 'Off' position.
On a/c cars there's a vacuum operated hot water shut off valve. Do you have the a/c controls set so the valve has been closed?
Regards,
Alan
Pro
Joined: Nov 2013
Posts: 730
Likes: 37
From: Catoosa Okla
My first question is do you have the manual shut off valve installed on your heater hose before the inlet of the heater core?
The way GM designed the heating system allowed water to flow through the heater core at all times.
It didn't take long to realize this wasn't the best idea, and as a quick fix, dealerships installed a manual shut off valve the the owner closed off in the summertime and opened during winter months
The way GM designed the heating system allowed water to flow through the heater core at all times.
It didn't take long to realize this wasn't the best idea, and as a quick fix, dealerships installed a manual shut off valve the the owner closed off in the summertime and opened during winter months
Last edited by Patro46; Feb 21, 2017 at 09:15 AM.
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,062
Likes: 266
From: Slower than a speeding bullet................ Fort Lauderdale, FL
Hi MRW,
Do you have an Owner's Manual for your car? It explains the operation of the heater/defroster or a/c controls for your car.
You don't mention if your car has a/c or not.
Since you mention "vents in front of console" I'm thinking a/c?
On non a/c cars the blower motor runs at 'Low' all the time, there's no 'Off' position.
On a/c cars there's a vacuum operated hot water shut off valve. Do you have the a/c controls set so the valve has been closed?
Regards,
Alan
Do you have an Owner's Manual for your car? It explains the operation of the heater/defroster or a/c controls for your car.
You don't mention if your car has a/c or not.
Since you mention "vents in front of console" I'm thinking a/c?
On non a/c cars the blower motor runs at 'Low' all the time, there's no 'Off' position.
On a/c cars there's a vacuum operated hot water shut off valve. Do you have the a/c controls set so the valve has been closed?
Regards,
Alan
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,062
Likes: 266
From: Slower than a speeding bullet................ Fort Lauderdale, FL
My first question is do you have the manual shut off valve installed on your heater hose before the inlet of the heater core?
The way GM designed the heating system allowed water to flow through the heater core at all times.
It didn't take long to realize this wasn't the best idea, and as a quick fix, dealerships installed a manual shut off valve the the owner closed off in the summertime and opened during winter months
The way GM designed the heating system allowed water to flow through the heater core at all times.
It didn't take long to realize this wasn't the best idea, and as a quick fix, dealerships installed a manual shut off valve the the owner closed off in the summertime and opened during winter months
I would install one if it would help my problem.
Team Owner
Joined: Sep 2006
Posts: 31,289
Likes: 4,380
From: Westminster Maryland
Hi MRW,
The vents you describe are part of the floor diffuser for the heater.
Are you certain the hot/cold wheel on the right side of the heater/defroster controller on the console is in fact opening/closing the door in the heater box that controls hot/cold?
It's a 'bowdon' type cable.
You should be able to look under the right side dash pad and see if the cable is actually moving the lever on the door.
Are the kick panel vents operating properly?
Are the astro-vents in the corners of the dash pads operating properly?
Regards,
Alan
The vents you describe are part of the floor diffuser for the heater.
Are you certain the hot/cold wheel on the right side of the heater/defroster controller on the console is in fact opening/closing the door in the heater box that controls hot/cold?
It's a 'bowdon' type cable.
You should be able to look under the right side dash pad and see if the cable is actually moving the lever on the door.
Are the kick panel vents operating properly?
Are the astro-vents in the corners of the dash pads operating properly?
Regards,
Alan
Last edited by Alan 71; Feb 21, 2017 at 02:14 PM.
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Instructor
Joined: May 2016
Posts: 178
Likes: 22
From: Vermont
My 71 454 had a similar heat problem. Installed a shut-off valve in the heater hose & reduced cabin temp about 30%. I also discovered that both shifter (4 speed ) boots were dry-rotted & had large holes, allowing heat to enter the cabin. I'm now installing the trans. tunnel insulation blanket & horseshoe-shaped insulation between the upper bell housing and body.
Your vent problem has been explained above. But if you do not insulate the cabin, that 454 is going to roast you.
Tim
Your vent problem has been explained above. But if you do not insulate the cabin, that 454 is going to roast you.
Tim
Team Owner
Joined: Jun 2001
Posts: 23,381
Likes: 1,067
From: Virginia USA
If it's blowing out of the small vents at the center console (by your right foot as the driver and left foot as the passenger) then I'd look at your cable connections as Alan described. This is where the heat comes out when using the heater. Seems your diverter door is in the Heat on position.
If it's a non-ac car you should have two levers on either side of the console to open the Astro-ventilation doors that are located in the kick panels by your feet. This will let in fresh air.
Remember these cars interiors run a little hot. You are basically sitting on the transmission and your feet are right next to the engine. There should be heat shields on the firewall by your feet in the engine compartment and also a foam collar that keeps engine heat out of the transmission tunnel. It sits on top of the bell housing and is pressed in between the tunnel and bell housing.
Heat management takes a little work with these cars.
If it's a non-ac car you should have two levers on either side of the console to open the Astro-ventilation doors that are located in the kick panels by your feet. This will let in fresh air.
Remember these cars interiors run a little hot. You are basically sitting on the transmission and your feet are right next to the engine. There should be heat shields on the firewall by your feet in the engine compartment and also a foam collar that keeps engine heat out of the transmission tunnel. It sits on top of the bell housing and is pressed in between the tunnel and bell housing.
Heat management takes a little work with these cars.
Race Director
Joined: Oct 2008
Posts: 19,240
Likes: 1,673
From: Long Island
71 cars did have a Vacuum hot water shut off valve, 72 did not.
I have one on my 71 and do not have one on my 72. The vacuum port is one the selector on the 72 but blocked. I may sneak one on to the 72.
If the vacuum to the valve is missing the hot water will flow into the car. The mixing door in the heater will divert the heated air, but the air can still be warm. Especially when the seals on the door are shot.
If the hood seal is missing from the rear of the hood, hot air MAY be forced out from under the hood and into the vent intake.
Another good source is missing plugs on the firewall.
I have one on my 71 and do not have one on my 72. The vacuum port is one the selector on the 72 but blocked. I may sneak one on to the 72.
If the vacuum to the valve is missing the hot water will flow into the car. The mixing door in the heater will divert the heated air, but the air can still be warm. Especially when the seals on the door are shot.
If the hood seal is missing from the rear of the hood, hot air MAY be forced out from under the hood and into the vent intake.
Another good source is missing plugs on the firewall.
Team Owner
Joined: Sep 2006
Posts: 31,289
Likes: 4,380
From: Westminster Maryland
Hi B72,
"71 cars did have a Vacuum hot water shut off valve, 72 did not."
I'm not sure if you're referring to non a/c or a/c cars.
I believe in 71 only cars WITH A/C had a hot water shut-off valve in the heater hose.
Don't want folks to be looking for something that's not there unless an owner added it.
Regards,
Alan
"71 cars did have a Vacuum hot water shut off valve, 72 did not."
I'm not sure if you're referring to non a/c or a/c cars.
I believe in 71 only cars WITH A/C had a hot water shut-off valve in the heater hose.
Don't want folks to be looking for something that's not there unless an owner added it.
Regards,
Alan
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,062
Likes: 266
From: Slower than a speeding bullet................ Fort Lauderdale, FL
If it's blowing out of the small vents at the center console (by your right foot as the driver and left foot as the passenger) then I'd look at your cable connections as Alan described. This is where the heat comes out when using the heater. Seems your diverter door is in the Heat on position.
I'm not very mechanically inclined, and will have a friend with more knowledge look at this next week. He owned a '70 bb for about 20 years and hopefully can assist me.
Thanks to all for your suggestions.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Those heater air boxes have seals that dissinigrate over time. There is a door inside that seals cool air from hot. Dr Rebuild sold good new seal kits and maybe still in business. The outer box seals used what was called monkey poop but I just used RTV on mine.
Good luck.
Good luck.
Last edited by cardo0; Feb 25, 2017 at 09:18 PM. Reason: Stupid autocorrect!