So my read out on my overhead either works or it doesn't. Some day it will give the correct temp all day. Some days it will work for 5 mins and stay on the same temp all day. Example it will be 65 sit at work til noon get in it when it is about 90 and it will be reading 65 still. It worked all yesterday and read 84 when it was parked last night. That is what is was stuck on today was 84. So is the sensor having a bad connection or what? BTW the compass and other functions are working as normal. Thanks in advance!

 

i would think its a bad temp sensor, its on the passenger side in the grill, next to the radiator

 

It could very well be the sensor but, also keep this in mind.....

From the 98 FSM:

THERMOMETER
The thermometer displays the outside ambient
temperature. The temperature display can be
changed from Fahrenheit to Celsius using the U.S./
Metric button, located just rearward of the display
module. 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 if the
engine coolant temperature is above about 52° C
(125° F). If the engine coolant temperature is below
about 52° C (125° F), the thermometer will display
the actual temperature sensed by the ambient temperature
sensor. The thermometer temperature display
update interval varies with the vehicle speed.
The thermometer function is supported by an
ambient temperature sensor. The sensor is mounted
outside the passenger compartment near the front
and center of the vehicle, and is hard wired to the
module. The ambient temperature sensor is available
as a separate service item.
The thermometer, compass, and trip computer display
module cannot be repaired, and are only available
for service as a unit. If faulty or damaged, the
complete module must be replaced.

Hope this helps!

 

Yeah but when the thermometer on the garage says 70 and when it has been sitting over night it will say 88. This is after 15-20 mins of driving it will stay at that temp. It used to be great at how fast it displayed the temp and very accurate. Can it possibly be dirty or have a bad connection that was causing this? Thanks for the info.

 

More likely to have a bad connection than dirty... i would try replacing the sensor first but, its also possible that the temp part of the overhead is bad, leaving the rest to work properly.

 

Ok thanks, I just cleaned it. It had a big what appeared to have been a moth stuck on it and it was giving an accurate temp then. Which it hasn't done for a week or so after it has been driven and shut off.

 

Well, i hope that does the trick... new sensors run about $20-$30 bucks depending where you get them.

 

So my sensor was working fine until today. I was driving in town and like usual my engine temp went over 220. At that time it was 79 out. I was waiting in line to get lunch and my temp went up to 240. At this time my outside air temp was still reading 79. I finally got out of town and cruising at 55mph my engine temp finally dropped to 215 and then my outside air temp went to 89 which was right and continued to work properly until my engine temp goes above 220. I think I have an overheating problem not a sensor problem.

 

I agree it sounds like you have a overheating issue... i would drain the system and replace the T-stat and refill... don't to burp the system, in fact do yourself a favor... take the new T-stat and put it in boiling water, once it opens pull it out, put a asprin in there and let it close onto it... install the t-stat that way... as your filling the system the air will excape thought the top hose and as you get things running and it heats up the pill will disolve...

Also, i would test the radiator for hot spots that may be a clog in the there.. you can buy a thermometer to test that pretty cheap at your local auto parts store...

hope that help,
Old_School

 

Thanks, I'm leaning towards the radiator since the thermostat only has 20,000 miles on it and you can feel the hot water come out at 195 like it should. Thinking of putting in a 180 though. I will drive it and feel the radiator for different temps today. BTW I cleaned it yesterday and pulled back the exchanger to check for debris, it was pretty clean.