Anyone know of a way to disable the cabin air filter timer?

Every day for the last four years the timer on the air filter drives me crazy. It insists on switching from filter to outside air after three minutes, which sucks back in all the Diesel fumes and dust I just finished filtering. I would very much like to disable the timer. I'm not afraid of cutting wires.

 

This button

 

Weird. Mine doesn't work that way. When I press that button the fan speed doesn't go to high, it goes to whatever speed the fan was on when I last turned off the car (at least I think it's that - the speed that results from pushing that button changes. Sometimes it's low, sometimes it's medium, and sometimes it's high. Sometimes pressing that button makes the A/C button also illuminate and sometimes not.).

If the air is always going through that filter, what does pressing that button do when outside air is selected?

 

When driving on a busy freeway or major street, one is always driving in a stream of pollution that is particularly damaging to the lungs and heart. A one-hour commute with outside air intake doubles your exposure to ozone and particulates. If you commute for two hours a day like I do you are tripling your exposure. To combat this I always run the vents on recirculate while on busy roads or freeways, and I have installed a HEPA filter in my Prius that is powered by an inverter and it runs whenever the car is on.

The problem I have with the filter button is the way in which the Prius behaves when the 3-minute timer expires. Often it automatically switches from recirculate back to 100% outside air, which is then drawing in the unhealthy air from outside. Worse is that there is no indicator that this has happened other than the lights on the buttons. If you are busy watching the road you can go some time without noticing that your Prius is trying to kill you. This is also a problem when running the A/C as the Prius often automatically switches from recirculate to 100% outside air all on its own without asking me.

 

Of course not using a feature of the car that doesn't work the way I would like is an option, but I'd rather be able to use the feature without fighting with my car to get it to work the way I want.

If you have the A/C on it will switch back and forth between outside air and recirculate depending on the temperature outside. As far as I know there is no way to control this behavior.

Which is why it's such a mystery to me why Toyota designed the climate control system to behave the way it does. I can't think of world where it makes sense to give the user manual controls just to have the system override the user's input. If the ventilation system is going to do what it wants anyway, why are the buttons and knobs even there?

 

An average human at rest expels 20 liters per hour of CO2. At 2g/L, that's 40g per hour. OSHA allows workers to be exposed to up to 9g per cubic meter for 8 hours a day. The interior volume of the PiP is 3.265 cubic meters, which means we can fill it with up to 29.4g of CO2 before reaching the 8 hour exposure limit for CO2. The air does start out with somewhere around 1.3g of CO2 in it, leaving 28.1g for us to work with. If we target that level, and the cabin was otherwise airtight, it would be about 45 minutes before we reached that level. Since we've only been in the car 45 minutes at that point instead of the 8 hours a person can be exposed to that level of CO2, it's safe to say we'd be fine with higher levels. Cal-OSHA allows workers to be exposed to 9 times that much CO2 for 15 minutes. If the relationship between exposure time and CO2 level is linear, we could safely remain in an airtight PiP for about three hours. If the relationship is exponential it would be a tad over two hours.