Tpms, fault?,

[Primus1]

This morning the tpms alert came up, rear nearside tyre showed it had dropped to 27psi, checked tyre when I got to work and again later in the day, tyre seemed ok with no sign of going down, on the way home pressure was 28 psi, checked with gauge which showed 28.5 psi, I inflated it to 29, just wondering if temperature is anything to do with it, it was -4 this morning…

[FROSTYBALLS]

23 minutes ago, Primus1 said:

just wondering if temperature is anything to do with it, it was -4 this morning…

Probably

[Chippy01]

Cold temps lower the pressures.
But if, after double checking everything, the problem persists on the same tyre, check for a nail/screw that's causing a slow puncture.
My OH had just the same issue.......then we spotted the nail buried in the tread.

[Ralph H]

34 minutes ago, Primus1 said:

This morning the tpms alert came up, rear nearside tyre showed it had dropped to 27psi, checked tyre when I got to work and again later in the day, tyre seemed ok with no sign of going down, on the way home pressure was 28 psi, checked with gauge which showed 28.5 psi, I inflated it to 29, just wondering if temperature is anything to do with it, it was -4 this morning…

I could have written this on Tuesday the exact same thing happened to mine even down to the same wheel and same pressure. Definitely weather related pressure drops in low temperatures. 

[dash]

39 minutes ago, Primus1 said:

just wondering if temperature is anything to do with it, it was -4 this morning…

Almost certainly

[Jasper.]

32 minutes ago, Ralph H said:

I could have written this on Tuesday the exact same thing happened to mine even down to the same wheel and same pressure. Definitely weather related pressure drops in low temperatures. 

Same for me , when this happens it's always the nearside rear..🤔

[Primus1]

Seem a common thing, I don’t think I have something in the tyre, as I’ve had this before and the tyre did look slightly deflated, I’ll have to check again tomorrow..

[Chas G]

Ideal Gas Law:-

PV=MRT

[P=Pressure of gas, V=Volume of gas, M=Mass of gas, R=Characteristic gas constant, T=Temperature]

If the temperature goes down P goes down so as the weather has got much colder tyre pressure decreases and may bring on tpms alarm.

[Cyker]

Blimey I had no idea this forum was so high brow - I think you're the third person to quote the ideal gas law this month!   

For comparison, my Mk4 has a 4-5PSI delta from when get in it in the morning to when I get to work, according to the onboard display (It's currently my favourite thing - No more needing to check the pressures and fiddling with frozen fiddly valve caps with frozen fingers!  )

[Mojo1010]

Have a read here, someone is looking to move away from Toyota!

 

[Chas G]

13 minutes ago, Cyker said:

Blimey I had no idea this forum was so high brow - I think you're the third person to quote the ideal gas law this month!   

For comparison, my Mk4 has a 4-5PSI delta from when get in it in the morning to when I get to work, according to the onboard display (It's currently my favourite thing - No more needing to check the pressures and fiddling with frozen fiddly valve caps with frozen fingers!  )

I suppose factoring in the elasticity of the tyre would have over complicated the explanation. 😀

[Derek.w]

Probbably just down to the climate lower temperatures my car just complained about the two rear wheels yesterday & my tyre inflator packed in so this was my work around 2 rear then the front one adding some air.

Just need to remove the Battery pack is my next step.

[Bernard Foy]

This morning, temps -4. Nearside rear showed tyre pressure warning light. Got out of the car, it looked ok, so I ignored it, but by this evening I couldn't ignore it any longer so I got the pressure gauge and it showed 31psi. Got the wee compressor put brought it up to 32psi, light gone. So definitely the freezing temperatures is the culprit. 

[Mojo1010]

Knew Chas was like Einstein when he came up with 'theory of 12v'.  

[PortlandBill]

In the winter you have to put more air in your tyres, in the summer you have to let some out. It's been like that forever. Why are people only realising that now? 

[Ralph H]

51 minutes ago, PortlandBill said:

In the winter you have to put more air in your tyres, in the summer you have to let some out. It's been like that forever. Why are people only realising that now? 

Because in the old days everyone drove around happily with “flat” tires without the car bonging at you 

[HarryW2024]

I’ve had this of late, I’ve also had comprehensive tpms’s on other marques  and never had the need to put air in over winter. I’ve topped up now but wonder if the factory air is overly humid as moisture content is a big effector on pressure changes with temperature.

don’t get me on the ******* AC system that struggled to keep the Insides of screen dry and not fogged up on a 2 hour journey last night (4 hour in toto), again never had that issue on a AC equipped car since the 80’s…. Not good on twisty A roads with on coming lights dazzling being magnified by it.

[dash]

Was your heating system set on Eco? Wondering if that reduces effectiveness of AC

[flash22]

its always been my front right that drops happens every year when the temps drop

seems 4 psi is the delta, the tyre had 29 psi in it, the dash said it wanted 33

[flash22]

3 hours ago, Ralph H said:

Because in the old days everyone drove around happily with “flat” tires without the car bonging at you 

you also had a set of points, a spark plug, an oily rag wedged down the side of a metal can of Duckhams 20w50, random spanners and a rusty set of feeler gauges, if it was a British-made car you also had a tin of 3in1 and a dustpan and brush

[forkingabout]

1 hour ago, HarryW2024 said:

don’t get me on the ******* AC system that struggled to keep the Insides of screen dry and not fogged up on a 2 hour journey last night (4 hour in toto), again never had that issue on a AC equipped car since the 80’s…. Not good on twisty A roads with on coming lights dazzling being magnified by it.

Missus never has an issue with her 24 MY Yaris Cross Excel.

Auto A/C on in normal with temp set to 22 deg C

[forkingabout]

1 minute ago, flash22 said:

you also had a set of points, 

I remember setting dwell angle on points when I was younger using a Gunson Autoranger 

[HarryW2024]

28 minutes ago, forkingabout said:

Missus never has an issue with her 24 MY Yaris Cross Excel.

Auto A/C on in normal with temp set to 22 deg C

Yep, normally run it on auto 22c and never had a problem on any of my cars before. I had to switch it to demist mode after a while. Then did it manually with medium fan speed and screen/feet direction selected as demist was noisier than the rest of the car.

as said never had a car that can’t keep on top of misting when auto selected once you’d warmed up. Another nail in the coffin for this car…..

[HarryW2024]

I will add only car since a 1970’s Alfasud that fails to meet even the most basic refinements for passengers….

[forkingabout]

You havent got air recirculation switched on? 

This seems to be a favourite with Toyota hybrid owners who then complain about the cabin misting up.