Outside air temp gauge

Pretty sure I have seen 104f in the past. At the moment it is reading 96f in a garage which is accurate.

 

I saw 106F a week ago, on the other side of this state. Regular 2012 Liftback, not v.

 

how long are you out there? mine takes about an hour to reach full temp after leaving the garage

 

The only time my outside temp is wrong is after a car wash. It will read 10-15 degrees low before it dries off. Maybe ten minutes.

 

Not really surprising that it might be bad after 10 years.

But it is trying to read the temp where it is actually located which is always in the shade.
And if the car is not moving and not running, the metal body might be slow to heat up.

It bears some observation in various conditions before you decide that it really is "bad".

 

Thermistors rarely go bad from a calibration standpoint. They sometimes open and more rarely short which are detectable conditions. About the only way to be 13 degrees low is through a high resistance connection given a ntc thermistor.

 

What about the rest of the electronics that translates the current flow into a numerical reading ?
The "fix" for this might not be as easy as the OP imagines.

 

A to D converters are not in the eighties these days.

 

Meaning what exactly ?
Regardless of design, it can fail.

 

FWIW, OAT probe on the 1996 Dodge Grand Caravan failed after 10 years... Easy plug and play fix.

 

Replacement might be simplest, if it’s cheap. If it’s costly and you want to diagnose: I don't have Prius v, but here's some Repair Manual info hopefully similar:

Temperature range:




Trouble code:




Attached is the trouble-shooting procedure for above DTC code. Again, hopefully is similar for the Prius v.

 

I'm with rj in thinking a connection adding to the NTC thermistor's apparent resistance (and thereby reducing the reading) probably more likely than badness of the thermistor itself.

Replacing the thermistor might well fix it ... because you would have unplugged and replugged the connector where the extra resistance probably is.

 

[QUOTE="rjparker, post: 3373079, member: 41651"... About the only way to be 13 degrees low is through a high resistance connection given a ntc thermistor.[/QUOTE]That condition would adversely affect readings at all temperatures. Lildevil wasn't clear whether that's the case (vs. malfunctioning only at T>85°)

 

All the same, I haven't heard of a thermistor itself going bad in some "only at T>85°" way either.

Because the resistance of the NTC thermistor goes down as temperature goes up, if there is some extra fixed resistance in the circuit somewhere, it will be a bigger proportion of the total resistance when the temperature is higher. It will always make the reading too low, but by worse amounts at higher temperatures.