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I have the age old hot passenger footwell area and hot sill problem.
I have done some research on this topic now, to the point where I am now even more confused about the HVAC system in my car.
Going from front to back;
1) I have checked the servos and the 2 mixers work and the fresh air servo work. The footwell and defrost servo don’t work properly but I think this might be a story for another time and I don’t think they should impact this problem, but I am happy to be educated so please let me know if otherwise.
2) I checked both fans upfront work. I also opened the passenger side blower casing to check the servo is actuating the little door and this works too. If you are interested to see these in action then there is a video here:
Additionally, it might useful to point out I noticed the entire fan housing on the passenger side seems to be hotter than the drivers side which is cool to touch.
3) I removed and checked the cardboard hose in the passenger footwell and it does not seem to have any visible holes in it, even though it has probably seen better days (see photo below). This, particularly the jubilee clips on it, get very hot.
Additionally, I did notice the jubilee clips on the drivers side also get hot on this cardboard pipe though, even though I don't seem to have the more general heat in the footwell problem on that side.
4) Today I listened out for the rear heater flaps on the heat exchangers making the “clack” noise when closing the door with the windows up and I heard it. So the flap seems not to be stuck.
Here I have a couple of clarification questions though:
a) I think I heard one of the rear flaps on closing the doors, is this actually just one of the flaps moving position due to the interior pressure increase caused by closing the doors or are both flaps moved?
I am just wondering if this could be a way to check both flaps on both sides are not seized.
b) I read somewhere you have to have the heat on, then turn the ignition off and attempt the door closing test for the flaps to make the “clack” sound. So I assume the flaps are resetting from the open position, letting heat forward to the default closed position, venting out. Is that right?
c) The problem I have with b) in my case, is that I obviously don’t want heat so the CCU is set to cold, which should mean the flap is already in the default closed position, venting out. But of course heat is getting forward so the flap must be open letting the heat forward, but why if on door closing it moves to the default venting position again?
Am I missing a piece in the equation? Maybe a piece in the system which I am unaware of which should be checked. The complexity of the system is making my head spin.
Any help or advice very much appreciated.
I have to say the last time I had the HVAC system recharged was May of 2017 and one the things that I do in the summer and this may help you as well is I disconnect the hoses from the heat exchanger to the chassis flapper boxes, that way you get max cold air, And reinstall in the late fall,
It seems that our cars get old the heat seeps through the front mixing flaps, Because the foam edges that seals the flap starts to go bad. When you disconnect make sure you vent it outwards so that your not blow the hot air on your starter or wires.
I was stopped at traffic light two days ago and my vent temp was at 34F, 90 deg out and 56 percent humidity. my new VW vent temp blow ce cold at 29F. I would like to see how cold you're AC gets. Please share your pic's
Thanks for your reply. I like the idea of disconnecting the pipe running from the heater flap box at the back. I only use the car during the summer anyway, so no heat should not be a problem. This is the next section of the system which I will have to investigate.
So when you remove the hose at the back, do you then tie it in place somehow to prevent blowing hot air, as you say, at your starter motor, etc.?
Something else I forgot to say was, my car does not have AC.
Something else I have discovered is that my interior vents on the passenger side, so the middle and one next to the glovebox do not really blow any air out. The other 2, drivers side centre and the one near the steering wheel do. That also seems a bit strange to me.
Any ideas how the air is split between the 2 sides? If the blower fan didn't work on that side I could understand, but it definitely does.
Number 3) above.
I decided to take another look at the cardboard hose in the passenger footwell because it is in bad shape and I wanted to make sure since this seems to be the only ? in the system. Well upon reinstalling it (second time now) it did indeed rip a hole in it
So now I definitely have a problem. It sorted the dilemma of to change or not to change though. So I will be replacing this and report back for, hopefully, sake of closure.
One question for the expert though:
Am I buying the left or the right hose? From which perspective is this? From the front of the car looking towards the back or from the perspective of the driver?
Is the passenger side pipe hot while driving normally? If so, you have 1 of 2 issues:
the passenger side rear flapper is stuck or not closing, pull tire, get car on jack stand, and check it out, it should move freely and when car is running you should feel a lot of heat in the footwell
The flapper in the heat box passenger side not sealing all the way allowing the rear flapper to direct heat into the wheel well.
based on your video, i suspect the rear flapper is not diverting fully and you're getting some heat forced into the car.
This happened to me once when I had a pretty great spin while on the race track, somehow stuck the flapper in the rear, had heat the whole way home, was able to knock it loose again and haven't had the issue since.
I would not buy the official Porsche cardboad to replace your pipes. Instead, order a section of high temp silicone or neoprene air-duct hose in 3” dia (same as the Porsche size). Much more durable and flexible and a bit less expensive. I used a section of the black (neoprene) for the inside pipes and the orange (high temp silicone) for the outside pipes near the motor.
The first thing I did was ask my indie to check the flapper boxes and he said there was no issue there. I can definitely hear one of them clang sometime when closing the door with windows closed. Which of the 2 are making the sound I cannot tell so one of them could still be on the blink.
@Spyerx - So if you take the wheel off and look down the outlet of the flapper you should be able to stick something down there to open and close the flap?
@jonathant - Good tip on the silicone hose. I don't suppose anyone knows how long this should be to fit? My old one is in such a state, if I try to straighten it to measure its length I assume it will break up completely and then I will be left with no hose until I can source a new one. I presume not having any hose in place is going to render the car undriveable.
No relation to Pegasus, and they sell the identical ducting a bumch of places (e.g. Aircraft Spruce).
I went black under the dash because the 300° rating was plenty there, and orange under the car since it’s close to the exhaust and the 500°+ rating can’t hurt.
Cuts with scissors except for the wire (use dikes) and is really easy to install. Get new band clamps for under the car also; mine were rusted up pretty badly.
Should be fine to drive without the hoses. If you take out the interior hoses I’d cap off the floor openings with metal foil hvac tape but otherwise should be fine I think.
The first thing I did was ask my indie to check the flapper boxes and he said there was no issue there. I can definitely hear one of them clang sometime when closing the door with windows closed. Which of the 2 are making the sound I cannot tell so one of them could still be on the blink.
@Spyerx - So if you take the wheel off and look down the outlet of the flapper you should be able to stick something down there to open and close the flap?
@jonathant - Good tip on the silicone hose. I don't suppose anyone knows how long this should be to fit? My old one is in such a state, if I try to straighten it to measure its length I assume it will break up completely and then I will be left with no hose until I can source a new one. I presume not having any hose in place is going to render the car undriveable.
You 'll see the output. You can remove one of the red pipes to see inside it, but it's tight off the heat exchanger. See the below thread. YOu'll see how it works. Closing the doors won't be the real way to test these. If that flapper spring isn't closing all the way you'll get heat pushed forward.
Removing the hose and taping up the entrance in front of the door sill is a good call. Maybe I can test the functioning of the flapper that way as well. I presume with a sealed system front of the flapper box, the flap should exhaust to wheel well.
Is regular 3M aluminium tape sufficient to tape up the hole?
@JasonAndreas - I'm guessing the 2 hoses are not the same length (964 572 528 01 Right, 964 572 527 01 Left), they have different prices.
Thanks for this timely thread, and thanks Heliops2 for the suggestion to disconnect the hoses at the flapper box which I am doing right now.
I suddenly noticed that that heat is pouring into the car from the rear. The left driver side door sill was cooking, and so was I. And there’s heat pouring through the right side by the vent under the rear side window. Not a fun ride home.
I did have a major spin out at the Autocross the weekend before last. Wondering if I jammed the flappers like Spyerx did. But right now I don’t want any more heat!
09-03-2018, 05:56 PM
Footwell Heat / Hot Sill Again
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