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Heater airflow significantly weakens when temp is set to ‘hot’

D

Diron

New member
Hi, I have a problem with the heater on my Grand Prix GT 2003 with dual zone manual temperature control.
The problem is that the air flow is close to nothing when the temp sliders are moved to maximum 'hot'. The air is hot though. When sliders are in 'cold' position - the air flow is nice and strong.

What I've done or checked by now:

- I've flushed and cleaned the cooling system. The heater core output pipe is almost as hot as input one. So I don't think the heater core is clogged. And I had a new one installed about 2 years ago.

- Blower works fine

- I've checked the Air Flop Actuators (both of them). I saw that the metal pin in the middle moves nicely from one max position to another max position (according to the marks on the plastic housing). I did not remove the actuators though and did only a visual inspection.

About 2 years ago my old heater core started leaking coolant and I had it replaced. Also the Dexcool was replaced with the regular coolant.
I think there is something mechanically blocking the airflow through the heater core. I think they could leave something there or did not remove some protection film when installing the new unit.

Do you think that blocking is a plausible reason?

Do you think I can check it without removing the heater core?

Thank you!
 


pretty sure the vac air flops things only move where the air comes from, the actuators control the temp of the air coming into the car. turn the heat to max temp and then remove the actuator on the side thats not right then turn it by hand to see if it turning all the way.
 
yeah thats it. sometimes the gears break inside and they wont turn fully. but if you can see it rolling back and forth and it get hot and cold they should be ok.

there is a blend door up behind the glove box in the dash, maybe thats hanging up, its vacuum operated.
 
Thanks again!
I've just checked the "Recirculation Door" - it moves freely and according to the spec (opens at MAX and closes when flow is sent to the floor). It has zero effect on the air flow strength. I move it with a hand - nothing. It means there is nothing blocking the air flow before it enters the blower motor.
Checked one more time electrical actuators - they move nicely and the air flow dies gradually as it moves from cold to hot.
To me it looks like the block is behind the flaps/doors operated by the electrical actuators.
Any suggestions?
 


I think my only option now is to get to the heater core and see what blocks it. If I"m lucky I see something in front of the heater. A fun weekend project )
 
heater cores at the bottom in the center of where the all the vac and actuators are, there are layers of stuff on top of it, your looking at a back breaking weekend, pull the console and the front seats, it will make life easier for sure.

and there is a bolt where the tubes to the core exit the car at the fire wall from the inside, make sure to remove that or the core may break on you. its on driver side of the inside of the car. at least it was on my regal, it cant be that different. a 1/4 drive nut driver for small sockets and and extension for it will make life easier too. and a good light.
 
oh and pull the heater hoses first and blow out the core, so you dont spill any coolant inside the car when you take it out.
 
Yeah, I realize how much fun it will be. I've seen some step by step instructions with pictures on this forum and I have that special software installed with all procedures and diagnostics.
Thanks for the tips! I'll post picts if I find a squirrel nest there )
 
The heater core is out. Looking nice and new, nothing blocks air on either side. No alien objects in the system as far as I can see. Temperature air flaps driven by electrical actuators move well - I can see them now.

I'm out of ideas now (
 


not trying to jack a thread here but its kinda happening, my car never heats up now that it is winter maybe 120 is the top , this sound like a problem?
 
Guys, could you please check if you can feel a difference on you Grand Prixes in air flow strength when moving sliders from 'cold' to 'warm'?
Thanks in advance!
 
Here is how the story ended: While the core was out, I back flashed it with tap water and blew throw it. Some dirt came out, not too much, but noticeable amount. Looks like the Preston cleaners have not done a good job here.
I've put everything back together and so far I think my problem is kind of solved. I realize that back flashing the core has nothing to do with the air flow strength, but it seems to be back to normal. Why? I don't know. The air temp though got hotter as well as the core output pipe. May be that gives a feeling of a better air flow.
The good thing is that now I'm a heater core replacement expert! ))
 
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