Tyre Pressure warning but pressures ok

[plisken]

I normally set my pressures at 37 and forget about them and indeed I dont think I have checked or adjusted mine for over a year, however have noticed them drop over time, which I believe is pretty normal and especially in the colder weather, I have seen them at 32 on start up which of course increases with temperature. The thing is, I have never had the low pressure warning until this morning, first on the left rear while at cruising speed and then around 20 minutes later the front right, as can be seen in the picture when stopped.

I put some air in the red ones and they of course went white and the warning lamp went out but my question is really, why has this never happened before when I know I have run as low as 32, possibly even 31 on very cold mornings?

Any thoughts?

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[CorvZ061]

Your photo reminded me of this from my old JL. Only the one tire it though was low, later on that day 3 were marked low but all had warmed up to showing more pressure.

 

[Nokones]

Tire pressures will also fluctuate up or down depending on the ambient temperature.

If you install a FlashCal ot Tazer, you can readjust the minimum tire pressure warning setting to your liking.

 

[2nd 392]

If a cold morning pressure drop to 28 psi the warning will come on, even if it comes back up over 28 when it warms up the warning will stay on until raised to 37 psi. I got tired of raising to 37 to shut it off, then back down to 30-32. The Tazer lowering the threshold to 25 psi has eliminated the PITA.

 

[Left Field]

I normally set my pressures at 37 and forget about them and indeed I dont think I have checked or adjusted mine for over a year, however have noticed them drop over time, which I believe is pretty normal and especially in the colder weather, I have seen them at 32 on start up which of course increases with temperature. The thing is, I have never had the low pressure warning until this morning, first on the left rear while at cruising speed and then around 20 minutes later the front right, as can be seen in the picture when stopped.

I put some air in the red ones and they of course went white and the warning lamp went out but my question is really, why has this never happened before when I know I have run as low as 32, possibly even 31 on very cold mornings?

Any thoughts?

My experience has been if it drops below 32 psi the warning comes on and the pressure has to be above 36 psi for the warning to go away, and even then it sometimes seems like it takes a while. There might also be some temperature correction or averaging going on that we do not have visibility to.

It gets complicated a bit by the fact that the tire pressure readings don't update immediately upon startup but seem to settle on the actual values after driving a short distance.

 

[6.2Blazer]

If a cold morning pressure drop to 28 psi the warning will come on, even if it comes back up over 28 when it warms up the warning will stay on until raised to 37 psi. I got tired of raising to 37 to shut it off, then back down to 30-32. The Tazer lowering the threshold to 25 psi has eliminated the PITA.

Was going to say the same thing. If the low pressure threshold is 28 psi and the tire drops below that the warning is activated. Even if the tire then warms up and raised back above 28 psi the warning will stay on until you pump it all the way to the target value.
The original post, I would verify what the lower threshold is and bet that the tires in question dropped below that point at some time.
It is normal for tires to very slowly leak down over time. The tire pressure is also directly correlated to the outside temperature.....the colder it is the lower the tire pressure will be. As the outside temp increases so will the tire pressure. Also just driving will increase the tire pressure as the tires start warming up from that activity.

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