Heater feels like it is running when moving.

[tigernut]

- When I'm stopped, I feel no airflow.
- When I am moving, I feel strong (HOT) airflow through the heater vent between the speaker and window, almost as if the heater blower motor were on high (with the knob on the right side of the clock pulled out).

I've verified the heater blower motor is not running.

Can anyone tell me where the air is getting into the heater box so I can stop it and stay somewhat cool in 95 deg. heat without A/C? :L

Thanks!
Doug

 

[67HEAVEN]

tigernut,

If you're referring to the defroster outlet at the base of the windshield, be aware that the bottom of that fiberglass funnel does not attach to anything. The heaterbox outlet simply sits underneath it.

You may be getting hot air from an external (to the heaterbox) source...or...the doors inside the box may not be actuating properly.

Check below the defroster area (behind the radio) to see what's going on.

 

[tigernut]

Thanks 67heaven, that is a good idea. I'll take a look tomorrow.

I didn't think I should be getting air from the heater box, as I believe the air inlet faces towards the back of the car in the firewall, if I'm not mistaken.

 

[Dave65]

The air is coming in through the cowl vents and then to the heater box.

Inside the heater box are a couple of doors. One opens and closes in a way that either directs air across the heater core or around it, the other directs the air either to the heater outlets at the floor or through the defroster outlets under the windshield.

I would guess the first is stuck in a position that directs the air over the heater core. The second is in the position for defrost.

Dave

 

[JohnZ]

I'm with Dave - the "Air-Pull-Def" cable operates an internal door that allows outside airflow to enter the heater box, to pass through the core, and to flow out of the floor outlets, and when pulled fully out, diverts that airflow upward through the defroster ducts. The "Fan-Temp-Pull" cable operates another door that regulates how much of the outside air goes through the core vs. around it, to modulate temperature.

One or both of those doors are stuck (or the cables are disconnected at the operating levers on the heater box), and/or the foam seals on the ends of the doors that seal to the inside of the case have disintegrated, allowing airflow even with the doors in the closed position.

 

[tigernut]

I'm with Dave - the "Air-Pull-Def" cable operates an internal door that allows outside airflow to enter the heater box, to pass through the core, and to flow out of the floor outlets, and when pulled fully out, diverts that airflow upward through the defroster ducts. The "Fan-Temp-Pull" cable operates another door that regulates how much of the outside air goes through the core vs. around it, to modulate temperature.

One or both of those doors are stuck (or the cables are disconnected at the operating levers on the heater box), and/or the foam seals on the ends of the doors that seal to the inside of the case have disintegrated, allowing airflow even with the doors in the closed position.

Yes, that is what I thought. This hot airflow was happening before I replaced the heater core. When I replaced the heater core about a month ago, I replaced all the seals inside the heater box and checked operation of the doors.

I guess I just need to get off my butt and crawl under and do some investigation. I was just hoping for an "easy" answer.

Thank you all for your responses. I'll let you know if I find the culprit.

Doug

 

[tigernut]

FYI,

I had to adjust the cable mechanism behind the glove box that controls the inner door. With the dash knob all the way in, the door was still not shutting all the way, as evident by examining the pivot mechanism atop the heater box.

That cut down on the airlflow quite a bit, but I still get a slight flow of air through the heater box when driving at 50 mph or more. I'm not sure why I get the "ram air" effect through the heater box (maybe since I've removed most of the splash shielding???).

Anyway a rag in the bottom of the heater box vent took care of that minor annoyance.

Now the only place hot air is coming in is via a few missing "plugs" that hold the firewall insulation in place. I need to order some new ones. It is amazing how much hot air comes through those holes (smaller than a dime).

My wife drove me around for the first time this weekend and I'm amazed at how much heat "radiates" from the heater box, when sitting on the passenger side.

Thanks to all for the suggestions.
Doug

 

[Tom Bryant]

One of the bad things about these cars was that there was no water shut off valve on the non-A/C cars. If you have any air coming through the core at all it will be expelling heat out of the ducts. An option would be to go to an auto parts store and get an inline water shut off valve and install it in the heater hose line that takes the hot water to the heater. Then you can shut off the line and the core will be cool. That will eliminate the heat blowing out of the ducts if there is any leaking past the doors and also the radiant heat in the interior from the core being hot. Just open the valve when the weather turns cool and you have a heater again.

Tom

 

[tigernut]

Thanks Tom, I hadn't thought of that. Sounds like a great idea.

 

[JohnZ]

Put the valve in the 5/8" hose that runs from the intake manifold fitting to the lower heater core nipple.

 

[Sky65]

One of the bad things about these cars was that there was no water shut off valve on the non-A/C cars. If you have any air coming through the core at all it will be expelling heat out of the ducts. An option would be to go to an auto parts store and get an inline water shut off valve and install it in the heater hose line that takes the hot water to the heater. Then you can shut off the line and the core will be cool. That will eliminate the heat blowing out of the ducts if there is any leakin past the doors and also the radiant heat in the interior from the core being hot. Just open the valve when the weather turns cool and you have a heater again.

Tom

Will this have a negitive affect on engine cooling?

 

[Tom Bryant]

No..

 

[brumbach]

I had the same problem and installed the shut off valve as recommended except I didn't use an inline. Instead, I installed one directly to the intake manifold. I can really tell the difference in the cockpit. No heat what-so-ever coming from the vents. Thanks so much for the remedy.

Bill

 

[Kid_Again]

I followed JohnZ's advice and it works perfectly. Absolutely no change in engine temp.

 

[sagnoff]

Sounds like it might help with the hot,humid Wilmincton NC weather. Can someone describe where the hose comes off the manifold?

 

[brumbach]

Sounds like it might help with the hot,humid Wilmincton NC weather. Can someone describe where the hose comes off the manifold?

From the front of the car, it is below and to the right of the oil fill tube.

 

[brumbach]

From the front of the car, it is below and to the right of the fill tube.

Sounds like it might help with the hot,humid Wilmincton NC weather. Can someone describe where the hose comes off the manifold?

 

[paul67]

Does anyone have a pic of one of these in-line shut-off plumbing valves. Are we talking Home Depot? I wish to install one.

 

[brumbach]

I don't have a pic but I purchased the shut off valve from O'Reilly Auto Parts. I would imagine Advance Auto or Autozone carries them too. O'Reilly 's had the inline version and also one that is threaded on one side which I purchased. I also had to purchase a bushing to complete the connection on my intake manifold. If no one purchases a picture tonight, I can in the morning when my son returns with his camera.

Does anyone have a pic of one of these in-line shut-off plumbing valves. Are we talking Home Depot? I wish to install one.

 

[paul67]

Thanks Brumbach,
I would prefer a hose unit. Those intake snouts scare me.