The Lotus Cars Community banner

1 - 7 of 7 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter · #1 ·
When i turn a/c on through dash vents, occasionally the sound of the air blowing changes to a slightly louder sound but less air comes out the dash events.

I am having this same exact issue, that was discussed in an old thread quoted below but no answer was given, it appears to be an issue with the air diverter/flap. where is that located on the car, looking to see if I can pull it/repair/replace it?



Rfong said:
This would be like a diverter in a house air duct? Where is it located in the Evora? That's what the malfunction feels like. Sometimes the AC is working fine, then suddenly the air flow shuts down to 10% of the flow. Same sound from the fan, just less air. Then, just as suddenly the air comes back full force.
 

·
Premium Member
Joined
·
1,735 Posts
It should be within the air distribution unit, which is inside/underneath the dash.
 

·
Registered
2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
Joined
·
588 Posts
That happens on other cars I drive (though not the Evora so far, thank goodness!) when I change the air routing. You can hear the air routing change until the ducts come to rest into whatever new setting I've selected (say, from full-face to feet+windshield). This makes me wonder if it's your control that has an issue. Perhaps the control has become intermittent, such that normal vibration causes it to "change settings" occasionally, and the ducts are just responding to that? I'd look into that before blindly swapping the ducts, as I suspect the former are far more accessible than the latter. Just an idea.

Separate but related note: I've noticed that the Evora GT's routing control knob is hyper-sensitive coming off of full-face. With the knob fully rotated to full-face, I get a nice blast of air from the four dash vents. But move that knob to even the very first click away from full-face and the percentage shifts dramatically to the footwell. It's easily 50-50 at the first click. I would have expected a more linear response. Not a "problem", just an observation.
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #4 ·
good point on the switch maybe being the issue, the way it goes back and forth while driving suggests the vibration could be affecting the switch
 

·
Registered
2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
Joined
·
588 Posts
I bet it's a potentiometer (variable resistor), not a switch. The detents are common on pots to give some tactile feedback but the element is one smooth wiping operation, as opposed to a switch with discrete contacts at each "stop". I could be wrong about this - it might be a switch - but I doubt it. It feels like a pot and a switch to control all those venting options would be far more complex than a simple pot.

More detail: A pot configured as a voltage divider gives you a varying voltage output based on the knob position. You drop that into an A/D converter to get a digital representation of the knob position, then use that digital value to decide how to control the ducts. This is very simple to do in firmware, but imagine how complex it would be to have a (say) 10 position switch where "toward one end" you want to ramp down on the face ducts, while "in the middle" you want to first ramp up and then ramp down the footwells, and "at the top" you want to ramp up on the windshield. That would require some hideous discrete electronics to make all of that happen. Instead, a simple and inexpensive pot gives you a nice voltage level and then firmware can decide what to do at any voltage in the range. Think: "The knob is at 37%? That means 20% face and 80% feet." You can do it via algorithm, lookup table, etc. Fast, easy, non-complex, and inexpensive.

One el-cheapo way to temporarily "fix" a dirty pot is to swing its wiper end to end several times at a modest speed. Pots which sit at the same location for long periods of time can experience wear where the wiper sits on the element, due to small vibrations basically "scrubbing" element material and creating physical contamination which then gets between the wiper and element. By "wiping" the pot end to end a couple of times, you can often clean things up a bit. It's not a permanent fix but might help reveal if yours is a pot, and not a duct, problem.
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #6 ·
Thanks, I will try the sweep several times to see what happens
 

·
Registered
Joined
·
511 Posts
That happens on other cars I drive (though not the Evora so far, thank goodness!) when I change the air routing. You can hear the air routing change until the ducts come to rest into whatever new setting I've selected (say, from full-face to feet+windshield). This makes me wonder if it's your control that has an issue. Perhaps the control has become intermittent, such that normal vibration causes it to "change settings" occasionally, and the ducts are just responding to that? I'd look into that before blindly swapping the ducts, as I suspect the former are far more accessible than the latter. Just an idea.

Separate but related note: I've noticed that the Evora GT's routing control knob is hyper-sensitive coming off of full-face. With the knob fully rotated to full-face, I get a nice blast of air from the four dash vents. But move that knob to even the very first click away from full-face and the percentage shifts dramatically to the footwell. It's easily 50-50 at the first click. I would have expected a more linear response. Not a "problem", just an observation.
Separate separate note: I notice same hyper-sensitivity on the temperature knob on my GT. If one moves just 1 or 2 clicks off full cold, seems to be a more exaggerated decrease in air temp.....more like ~50% drop? Works fine, just less linear as noted with routing knob....also, not a problem, just an observation!
 
1 - 7 of 7 Posts
Top