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Cold footwell over 70mph


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Having only recently started to need the heater since I bought the car in July, I have only just found out that it is difficult to keep the footwells warm when travelling in excess of 70mph - below that they are ok, not hot, but ok. All the controls work correctly at lower speeds, so I assume that somehow external air is finding its way into the cabin although there is nothing noticeable - is this unusual, or is it something you just live with?

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  • Gold FFM

Even with the heater "off" it still lets air through. This may be what you're getting. If you dial the heater to warm even with the fan off it does make a difference.

James Martin (JayEmm)
Director of Photography & Car Enthusiast

Follow my Lotus adventure online! www.jayemm.com

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Easy workaround is to turn on the recirculation button. That closed the "letterbox" opening through which cold air is pushed into the footwell.

If you have the choice between a Stairway to Heaven and a Highway to Hell don't forget the Nomex®!

Captain,  Lotus Airways. We fly lower! 

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7 hours ago, TBD said:

Easy workaround is to turn on the recirculation button. That closed the "letterbox" opening through which cold air is pushed into the footwell.

That isn't quite right. Turning on circulation works because the fan then draws air from the footwell rather than outside (which is what the footwell vent is for). The downside is you will start to steam up without the AC as all moisture is retained in the car. Short term fix is to cover the grille in the passenger footwell which is fine if you don't use recirculation. That stops cold air bleeding in at speed.

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  • 3 years later...

Thought I would try some one way face mask valves fitted to FR4 fibreglass panel -  hopefully should get over the recirculation issue.  If it seems OK  I'll make a few more from the left over valves from China an d put them on ebay.

vent plate1.jpg

vent plate2.jpg

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  • 8 months later...

I'm in the process of following Ken's suggestion to fixing the cold air draught in the footwell of my LE , before I do has anyone traced where the cold air is actually getting into the intake from in the first place my thoughts being if there is an outside airleek into that box section  it will be reducing the recirc efficiency as well as providing a cold draught when in normal mode and have lotus ever fixed it on the later cars ?

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Hi TRCM , thanks , yep I get that from the previous posts and the seloc wiki "fix" and Ken's above but but that's just the ducting from the footwell into the recirc system. What I'm trying to get to the bottom of is how the outside air gets into the duct in the first place without resorting to endoscope cameras n stuff.... I don't like fixing problems with work around if I can find the source.... Trouble with being an aerospace engineer.

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I'm guessing looking at this that there is no outside leak it's just that with the system as developed at a certain point the outside airflow pressure being rammed in gets big enough to "leak" through the fan drum and reverse the flow...

1327511284_Screenshot_20210622-1654222.png.0d79bb02fedacb1070410b3f4d559b32.png

Decent design would have had a motorised valve doing the opposite or similar of the outside air shutoff valve I guess..

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So had a bit if a play around on Fusion 360 for a few nights this week and drew up a panel with 2 diaphragm valves in the open and close depending on negative or positive pressure in the recirc chamber. It's only half the width as that's all my printer can handle and a blank plate for the other side. Opens alright to let recirc work but gets a bit whisley on full chat . Will see if it stops the draught in the foot well on Saturday on the run down to Silverstone for the British GTs. 

IMG_20210624_201839.thumb.jpg.ceb7014954dd663a932b513fa12873d6.jpg

IMG_20210624_201847.thumb.jpg.fef63dd2dae19d311ebea51fad72b91a.jpg

Installed

IMG_20210624_210422.thumb.jpg.2bc82a603d650590cd97d0b207e0ab0e.jpg

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@cdco is the fan stopping or is it that you get no airflow through any of the vents after a bit with the aircon on?

If the fan is stopping on speeds 1 to 3 it could be the fan speed resistors. They are cooled by the incoming airflow stream according to the Service Notes; I cannot see a separate resistor pack listed in the Service Parts so I take it that the resistors are integral to the HVAC housing, unlike on the Elise/Exige/Europa S where the fan speed resistor pack is external. If not, then it sounds like the fan motor could be the problem (overheating possibly?). Or it could be a combination of both on the settings below full pelt.

If it is a case of no airflow through the vents after about an hour it could be evaporator icing. My Launch Edition is prone to evaporator icing particularly when the aircon is set to full cold/recirc. I seem to recall a tech at a dealership I used to take the car to some years back telling me that it could be the thermistor positioning against the outlet side of the evaporator finning that is the problem (if it was U/S then there would be a fault code). I tend now not to use recirc unless I really must.

Hope that helps.

Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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@EuropaSman, thanks for this , it's Loss of airflow total all settings I don't tend to use recirc at all hence the engineering fix to stop the cold draught that ices your feet. I'll pull it apart soon but it's a front off job so will leave it till the back end. I've heard the icing before but more as a consequence of low gas pressure so had it regassed a month or so ago. Interestingly even if I put it on heat and by pass the cool air circuit I'm not getting any flow and can't hear the fan running. If it's "just" the resistor pack I'll have a look to see if it's repairable even though it's not listed as a separate part.

Frustrating but not the end of the world.

Ta C.

 

 

 

 

 

 

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Just re looked at the diagram and re read previous posts and  realised the airflow goes through the bloody evaporator no matter what so could still be icing. So next strop the drain tubes. Any one know if there is an actual fix for this without getting a later hvac unit

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Sorry, I don't know of a fix on the earlier HVAC units (I notice that they are now "E" spec and cost around £1600).

With the evaporator icing on my Evora, it usually has quite a bit of a wee-wee after a run of over half an hour with the aircron on. By the way could be worth checking when you look at the drain tubes that you have the SB 2010/03 drain tube routing/length modification embodied.

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Lover of everything Lotus Cars and proud owner of production Evora No.75 (2nd UK customer specced car by VIN). Originally from the Far East....of Anglia, I read black box data for a living so that could explain a lot!

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3 hours ago, EuropaSman said:

Sorry, I don't know of a fix on the earlier HVAC units (I notice that they are now "E" spec and cost around £1600).

With the evaporator icing on my Evora, it usually has quite a bit of a wee-wee after a run of over half an hour with the aircron on. By the way could be worth checking when you look at the drain tubes that you have the SB 2010/03 drain tube routing/length modification embodied.

Looks like I know what I'm doing this weekend. Though after the run back from work tonight there's a decent sized puddle forming near the nearside front wheel suggesting the drain is working.  

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