99 Jimmy - outdoor temperature sensor

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  #1  
Old 04-23-09, 07:47 PM
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99 Jimmy - outdoor temperature sensor

I have a problem with my outdoor temperature on my overhead read-out.

I thought it could be related to AC problem (automatic temperature controlled), but after solving the minor AC problem, I found out that the overhead temperature shown was just an outdoor temperature.

Now, usually, it makes little sense and I would like to get it a little more responsive and need to where the sensor is and how to clean it if it is being obstructed.

An example:

1. Went to work this morning and pulled the car out of the garage and the temp shown was about 60 degrees, which was probably correct.

2. I drove to the office with an outdoor temp of about 45 to 50 degrees and shut the car off.

3. I came out in the afternoon when the temp was about 80+. When starting the car, 51 degrees showed on the display.

4. I drove about 2 miles ( 5 minutes) and the temp went up to about 53 degrees. After getting on the highway, the temp held until about 5 miles later (5 minutes), when it quickly went up to 80 which was the local airport official temp.

5. Then it moderated and slowly went to the real local temp of 83 degrees.

It is not a big deal, but it is annoying and I should be able to get it more realistic and responsive after I start. Before this occurred, it always was realistic quite quickly, so it seems there is something affecting the sensor. When you are in Minnesota and can see 50 degree swings in a day it becomes important, especial around freezing. - That is the reason they have an "ICE" display at times when ice could be possible. - Driving near 32F can be dangerous if the conditions do change.

Where is the sensor and can it be cleared or replaced?

Thanx for any opinions and help.

Dick
 
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Old 04-24-09, 10:32 PM
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The system is designed to update after driving a few miles at a somewhat steady speed so it does not operate in an erratic manner.In other words it is working properly.Dirt does not affect the sensor since it is a thermistor type sensor.
 
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Old 04-25-09, 07:35 PM
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99 Jimmy - outdoor temperature sensor

It does seem to work reasonably well, except for the 10-15 miles it takes to reset or adjust the temp.

I have driven it for over 90,000 miles and never had this situation. My wife's 2000 Blazer is virtually identical and her car does not have the long delay when I tried it out on the same conditions when I compared recently.

After the Jimmy decides to reset/recalibrate after the 10-15 miles, it adjusts quickly to the conditions, when a cloud comes over or the sun goes down. It gets annoying when you have extreme daily temperature extremes, especially when you are 32F, where the temperature can be important.

Dick
 
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Old 06-26-09, 07:18 PM
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99 Jimmy - outdoor temperature sensor

davo -

I assume your description of the system is correct. - What I am trying to find out why my car is now acting differently than it has for the past 8 years.

Here is what I saw for the last 8 years with my Jimmy. -

In cold weather, I could pull it out of the tuck-under garage and initially it would say something like 50 or 60 degrees and quickly (within 300 feet) show a safety read-out saying "ICE" (if below 35 or so air temperature). After about a mile at 30 mph, it went to an accurate air temperature. This is a great feature with rapidly rising and lowering temperatures where ice can form.

In warmer weather the read-out would respond to high air temperatures within a couple of minutes (1 or 2). It was reasonably accurate compared to the airport temperatures, bank temperatures and local temperatures influenced by surroundings. - It was responsive and reasonably accurate.

Now this is what I see -

When I pull out of the tuck under garage, it takes a long time for it to respond. In cold weather, I never see the ICE warning unless the air temp is below 15 degrees. After a few miles I get a temp closer to reality, but not really reasonably accurate for 10 or 15 minutes.

When I drive to the office in the summer, I park the car in the morning when the temp says something about 65 degrees. When I come out at 4:00 PM when it is 90 degrees and start the car, it says 65 degrees until I drive several miles at 30 mph when it might go up to 66 or 67. After driving that 2 miles plus another 2 miles at 30mph and about about 8 miles on the freeway, it may go up to 70 or 72. Then about 3 or 4 miles later, it climbs from 72 up to 90 or so, which is the current local air temperature.

All of this has occurred recently and I would like to solve this problem that bugs me because of our radical temperature swings in a day that affect road conditions. There must be a reason.

I am not being paranoid since I also drive my wife's 2000 Chevy Blazer (an almost identical twin) over the same route and see no changes from what I saw 6 months ago on my Jimmy and that is different from what I see on my Jimmy today.

Could something be a simple as the routing of wires during my replacement of the intake manifold gasket? My local mechanic is also stumped and would like to find out what could be the cause since he has a lot of equipment and interest, but the wiring and sensors create some unique situations/problems.

Any opinions from anyone would be appreciated!!

Thanx - Dick
 
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Old 06-27-09, 08:28 AM
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not an expert on your car... but. could be that the car uses the air intake temp sensor ?? it may have been disturbed during the gasket operation... if you have a decent code scanner available.. you might check to see in the "datastream" to see if the temp is correct there . umm i think it will be called ait or iat ? can't remember off hand. if it is a separate sensor (not part of the maf sensor) then possibly it is twisted at an odd angle... ?( just a guess) could be that it's got a loss connection or perhaps it's not mounted up where it gets normal airflow over it. i usually find these lower on the car.. near the driver side bumber... but it could be anywhere. i thought that you can "reset" them ... by holding the buttons down iniside or something like that... very fuzzy memory there.
 
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