Ambient temp sensor

[GarrettChiesa]

Ambient temp sensor resets to 43f every time vehicle is started. no matter outside t

 

[brucejohnson]

Does the temp indication read any other value close to the actual temperature, or is it stuck at 43 degrees? A little more information on the truck and symptom details would help some too.

 

[GarrettChiesa]

Does the temp indication read any other value close to the actual temperature, or is it stuck at 43 degrees? A little more information on the truck and symptom details would help some too.

after couple minutes it reads the correct temp. if turn key off and restart it does the same thing

 

[brucejohnson]

GarrettChiesa,
Assuming you still have the 1999 Ram from your previous posts...
Do you know what the temp was when you shut the truck down from the previous use before the 43 degree indication on a current start?

Hopefully this excerpt from the 1998 FSM, which should be fairly close to a 1999, addresses your issue:

...
The displayed temperature is not an instant reading of conditions, but an average temperature. It may take the thermometer display several minutes to respond to a major temperature change, such as driving out of a heated garage into winter temperatures.

When the ignition switch is turned to the Off position, the last displayed temperature reading stays in the thermometer unit memory. When the ignition switch is turned to the On position again, the thermometer will display the memory temperature for one minute; then update the display to the current average temperature reading within five minutes.
...
​

Since you indicate the 43 degrees is a repeatable event with ignition cycling, it may be an issue with the module's thermometer memory or buss communications. A DRBIII session (dealer, or equivalent visit) would be needed to confirm the module function is OK or not.

 

[GarrettChiesa]

GarrettChiesa,
Assuming you still have the 1999 Ram from your previous posts...
Do you know what the temp was when you shut the truck down from the previous use before the 43 degree indication on a current start?

Hopefully this excerpt from the 1998 FSM, which should be fairly close to a 1999, addresses your issue:

...
The displayed temperature is not an instant reading of conditions, but an average temperature. It may take the thermometer display several minutes to respond to a major temperature change, such as driving out of a heated garage into winter temperatures.

When the ignition switch is turned to the Off position, the last displayed temperature reading stays in the thermometer unit memory. When the ignition switch is turned to the On position again, the thermometer will display the memory temperature for one minute; then update the display to the current average temperature reading within five minutes.
...
​

Since you indicate the 43 degrees is a repeatable event with ignition cycling, it may be an issue with the module's thermometer memory or buss communications. A DRBIII session (dealer, or equivalent visit) would be needed to confirm the module function is OK or not.

It shows the last temperature of current weather. Once the key is turned off it rests to 43f once restarted and then goes back to current temp. It work fine other then resetting .Now that i rechecked it. it also resetting the miles per gallon and miles on trip computer. I wonder if the fuse to keep the trip computer active during the key off is blow or something. All that works fine once vehicle is running. thanks

 

[brucejohnson]

It shows the last temperature of current weather. Once the key is turned off it rests to 43f once restarted and then goes back to current temp. It work fine other then resetting .Now that i rechecked it. it also resetting the miles per gallon and miles on trip computer. I wonder if the fuse to keep the trip computer active during the key off is blow or something. All that works fine once vehicle is running. thanks

That sure sounds like a unit memory issue. But why? Do each of the push buttons on the panel work independently and together as they should - displaying, paginating and resetting?

 

[Ozymandias]

I just replaced the sensor on my Gen3 for erratic temperatures and sometimes hanging for hours at the same temp.

Bought an NGK Sensor (OEM) from Amazon. All good now.
Sensor is the same kind from the early 90s all the way up to the Gen4. Amazing.