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.

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.

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

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

Blowing hot
 

Just FYI, I have a 1977 AC car and the blower fan is always on low.

Thanks Alan... No a/c. I read the owner's manual but as you say, there's no way to shut the fan off. These vents are not in the dash - they're in the footwell in front of console on tunnel.

No manual shut off valve on mine.
I would install one if it would help my problem.

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

http://imagizer.imageshack.us/v2/640...923/MMx2OM.jpg

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

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.

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.

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

It is blowing from the small vents by my right foot (with pretty good force).
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.

My '71 non-ac car doesn't have a heater core bypass valve. :thumbs:

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.