Outside Temp Sensor for Overhead display
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Mountain Pass
Joined: Sep 2009
Posts: 230
Likes: 1
From: Lower Mainland BC
Outside Temp Sensor for Overhead display
For some reason my OH display decided to show 140 deg F when its 40 deg F outside. Continues to show 140 all the time now regardless of out side temp. Anyone else had this problem and found a fix? In case its the related outside temp sensor sending unit anyone know where it is exactly on an 02. Unless someone has solution may try changing that out to see if that is the problem? Thanks for any help!
Cross-Country
Joined: Dec 2012
Posts: 57
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I was told it was either on the core support next to the headlight, if not there I saw a picture of one mounted to the driver side frame up next to where the tow hooks are.
I have one that I could not find in either location and am still looking for it, so if you happen to find it somewhere else I would like to know
I have one that I could not find in either location and am still looking for it, so if you happen to find it somewhere else I would like to know
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Mountain Pass
Joined: Sep 2009
Posts: 230
Likes: 1
From: Lower Mainland BC
Outside temp sending Unit.
THanks for feedback guys. I'll see if I have one behind grill. Part #? No one else who's had similar problems with wrong display temp with fix? THanks again!
Elder User
Joined: Mar 2012
Posts: 609
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The sender is nothing more than a temperature based resistor. The 140 temp indicates that there is an open or short in the circuit. They can be set up either way. You need to check the circuit from the sensor to the display.
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Mountain Pass
Joined: Sep 2009
Posts: 230
Likes: 1
From: Lower Mainland BC
How to check circuit
Thanks SRTEACH. Are you saying its not the sensor? If so as I'm electrically challenged can you help with how to check circuit. As all other display items are working didn't think it could it be a disconnect on the OH display circuitboard. Appreciate the help.
Elder User
Joined: Mar 2012
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I do know that the sensor gives variable resistance based on temperature. The board has a circuit that takes the resistance and converts into a temperature reading. The 140 reading you see is the board interpreting resistance. Since the reading doesn't change with different temps, there is either a problem in the OH console, bad wiring, or bad sensor.
It doesn't cost to measure resistance in the wiring and the sensor (if you have an ohmmeter), so I suggest you check resistance before buying a sensor.
The problem may or may not be in the overhead console, and the sensor could still be the problem, but eliminate wiring issues first.
In this list, OL means open or infinite resistance, depending on how your ohm meter displays it.
- You need to measure resistance at the overhead end of the connection (disconnected from OH display, leave the sensor connected) and compare it to the disconnected sensor resistance. If the measurement of the total circuit is the same as (or close to) the sensor resistance, the wiring is OK.
- If not the same, disconnect the sensor and check the wires again. IF it is OL, move to the next step. Any other reading means the two wires are shorted.
- Check each wire to ground (sensor still disconnected). If you get any reading (other than OL) at all, you have a short to ground.
Elder User
Joined: Mar 2012
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Unplugging will show if the sensor has failed by shorting, but if the sensor has failed open (infinite resistance), the readings will be the same when unplugged.
I just give advise based on experience with instrumentation and controls or electrical engineering. If I knew what type of RTD the sensor is, I could give better resistance numbers or a calculation based from temperatures.
For instance, A PT100 has a resistance of .0038 ohms + 100 per degree C. Type K has a different ratio, as does a type F or a type G. There are more than 15 different types, each with their own ratios and base readings.
My advise is freely given and may be freely rejected. Won't hurt my feelings a bit.
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Mountain Pass
Joined: Sep 2009
Posts: 230
Likes: 1
From: Lower Mainland BC
Thanks again Darrell, 73 and Jeff for help. Will do search for that thread on repairing the OH circuit board so I can see how to get at the leads. I think Woodnthings has a wiring diagram for my 02 which may help identify the wires. Do these sensors fail very often? If so may get a price and if not too bad just replace the sensor first to see if that fixes the problem. I'm not sure what I'd do if it was the wires! All the wires seem to be wrapped in bundles!