70 Heater Hoses

[RH 70 72]

Anybody with a 70 explain this setup in the heater hoses.? What it controls, how it operates? My 72 does not have this. TY

[MC1of80]

That is the heater control valve. On the 70 Monte Carlo it's located on the passenger fender well. For 71+ 72 it is on the intake manifold. 

It is supposed to shut off the hot water going into the heater core when the a/c is on or when cooler temps are requested. 

The quick version. Lol

[Dtret]

So it’s vacuum operated via the control panel on the dash correct?

[MC1of80]

Correct. 

[Leghome]

I did not think the 72 had those

[MC1of80]

Not 💯 on the 72. Has to have something though. 

Here is a pic of "barn find" 71 402

[Dtret]

9 minutes ago, MC1of80 said:

Not 💯 on the 72. Has to have something though. 

Here is a pic of "barn find" 71 402

That’s the same as my 71. Thanks for the information 

[jft69z]

None of my '72s (three of them) ever had that valve. I think it's done in the HVAC box with the blend doors, as far as choosing heat or cool air.

[RH 70 72]

9 minutes ago, MC1of80 said:

Not 💯 on the 72. Has to have something though. 

Here is a pic of "barn find" 71 402

My 70, which I’ve picked up recently are the pictures in the original post. My 72 has nothing inline on the hoses. The overarching issue is that I am getting warm air through the vents of the 72. Heater door opens and closes properly, temp control lever works. Wondering if this setup on the 72 would fix that

[RH 70 72]

2 minutes ago, jft69z said:

None of my '72s ever had that valve. I think it's done in the HVAC box with the blend doors, as far as choosing heat or cool air.

 I am getting warm air through the vents of the 72. Heater door opens and closes properly, temp control lever works. Wondering if this setup on the 72 would fix that

[jft69z]

Just now, RH 70 72 said:

 I am getting warm air through the vents of the 72. Heater door opens and closes properly, temp control lever works. Wondering if this setup on the 72 would fix that

Might work, but something else is probably wrong. May need to dig a little deeper.

[MC1of80]

Thanks for the 72 info. Only had a couple of them. Tons of 70 and 71s though. Lol

[RH 70 72]

24 minutes ago, jft69z said:

None of my '72s (three of them) ever had that valve. I think it's done in the HVAC box with the blend doors, as far as choosing heat or cool air.

Yup, my 2nd 72, not on either one of them. 

[Dtret]

Didn’t all these cars have “some” warm air coming from the vents with everything off? My chevelle does it also with no a/c. 

[RH 70 72]

36 minutes ago, Dtret said:

Didn’t all these cars have “some” warm air coming from the vents with everything off? My chevelle does it also with no a/c. 

My 70, no. My 72, yes. It’s a mystery to me at this point

[MC1of80]

A/c cars with a heater control valve should not have any warm air coming out the vents. 

[RH 70 72]

42 minutes ago, MC1of80 said:

A/c cars with a heater control valve should not have any warm air coming out the vents. 

My 72 has nothing on the hoses or the manifold. TY for your replies. 

[Leghome]

When I had my AC hooked up back in 2012 I had the same problem with heat coming in thru the heater vents  Could never find out how to fix it so I had a valve put in the heater hose that I have to manually turn off in the summer or my AC does not cool off the car at all.

[RH 70 72]

2 hours ago, Leghome said:

When I had my AC hooked up back in 2012 I had the same problem with heat coming in thru the heater vents  Could never find out how to fix it so I had a valve put in the heater hose that I have to manually turn off in the summer or my AC does not cool off the car at all.

Can you show a photo of that setup? 

[RH 70 72]

Thank you for all the replies. A shutoff valve has been placed inline on the 5/8” hose off the manifold. No leaks. No warm air. AC is back to cooling the cabin as designed. 
On to Carlisle !