'91 Coupe Outside air temp sensor?
Thread Starter
Heel & Toe
Joined: Oct 2003
Posts: 15
Likes: 0
From: Columbia City IN
'91 Coupe Outside air temp sensor?
Hi,
My radiator inlet recently cracked at the seam and blew. I towed the car to Berger Chevrolet in Grand Rapids Michigan to have a new radiator installed. Immediately before taking the car in, the "outdoor temp" gauge above the stereo read the outside air temp correctly. Immediately after getting the car back, the outdoor temp gauge permanently reads 50, regardless of the outside temperature. I don't live anywhere near Grand Rapids -- it was an emergency roadside repair while traveling, so I'm not too keen on taking it back for advice. My first thought is that the mechanics pulled a connector and forgot to reattach it. Or maybe they damaged the sensor if it's near the radiator, when working in the area. Or possibly when the radiator blew it soaked everything in boiling hot coolant, which damaged the sensor.
Long story short, where's the sensor located and what does it look like? My manuals don't say.
Thanks.
-k
My radiator inlet recently cracked at the seam and blew. I towed the car to Berger Chevrolet in Grand Rapids Michigan to have a new radiator installed. Immediately before taking the car in, the "outdoor temp" gauge above the stereo read the outside air temp correctly. Immediately after getting the car back, the outdoor temp gauge permanently reads 50, regardless of the outside temperature. I don't live anywhere near Grand Rapids -- it was an emergency roadside repair while traveling, so I'm not too keen on taking it back for advice. My first thought is that the mechanics pulled a connector and forgot to reattach it. Or maybe they damaged the sensor if it's near the radiator, when working in the area. Or possibly when the radiator blew it soaked everything in boiling hot coolant, which damaged the sensor.
Long story short, where's the sensor located and what does it look like? My manuals don't say.
Thanks.
-k
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
On my '88 the outside air temp sensor is located in front of the lower RH side of the radiator.
To easily see it look up through the front of the radiator air intake; in this case the sensor will be located to your left side.
The sensor has a little horn-shaped front end that helps draw air across the sensor.
To easily see it look up through the front of the radiator air intake; in this case the sensor will be located to your left side.
The sensor has a little horn-shaped front end that helps draw air across the sensor.
Thread Starter
Heel & Toe
Joined: Oct 2003
Posts: 15
Likes: 0
From: Columbia City IN
Thanks DeBaGo and 65Z01. Good info, very helpful.
I don't see anything resembling this sensor, mounted on or near the radiator. However there are two wires exiting a rubber grommet on the lower passenger-side of the radiator mount. The wires end in a dangling 2-prong connector. I'm assuming the missing temp sensor was plugged into that. It would be nice if I can order a new one from NAPA, not from a dealership. Anybody know the part number?
If it's really expensive, I'll write Berger Chevrolet, Grand Rapids Michigan, a nastygram. If it's cheap, well, whatever. Not real professional to forget to put it back on though.
I bought an FSM set online, and hopfully it will arrive this weekend. The Haynes manual was useless for this problem. Haynes manuals are ok for general repairs, but don't get very specific. I've heard (from this forum) that the FSM is a better resource.
- k
I don't see anything resembling this sensor, mounted on or near the radiator. However there are two wires exiting a rubber grommet on the lower passenger-side of the radiator mount. The wires end in a dangling 2-prong connector. I'm assuming the missing temp sensor was plugged into that. It would be nice if I can order a new one from NAPA, not from a dealership. Anybody know the part number?
If it's really expensive, I'll write Berger Chevrolet, Grand Rapids Michigan, a nastygram. If it's cheap, well, whatever. Not real professional to forget to put it back on though.
I bought an FSM set online, and hopfully it will arrive this weekend. The Haynes manual was useless for this problem. Haynes manuals are ok for general repairs, but don't get very specific. I've heard (from this forum) that the FSM is a better resource.
- k
Racer
Joined: Jan 2007
Posts: 486
Likes: 1
From: Jacksonville Florida
Thread Starter
Heel & Toe
Joined: Oct 2003
Posts: 15
Likes: 0
From: Columbia City IN
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
I would think they disconnected the plug when they pulled the shroud
and the sensor is still there.
Here's two pics. of the sensor. The thermistor is inside the black plastic housing.
You can see it's mounted in front of the AC Condensor on the passenger side. You can see it if you lay on your back in front of the car on the passenger side and stick your head under the spoiler area.
and the sensor is still there.
Here's two pics. of the sensor. The thermistor is inside the black plastic housing.
You can see it's mounted in front of the AC Condensor on the passenger side. You can see it if you lay on your back in front of the car on the passenger side and stick your head under the spoiler area.
Last edited by Hooked on Vettes; Mar 29, 2007 at 01:40 PM.
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Advanced
Joined: Apr 2005
Posts: 60
Likes: 0
From: Brighton IL
Me too
I have the same thing, a code 03, and found that the sensor was unplugged after a radiator swap last weekend, I plugged it back in and the code reset. The problem is that the temperture still reads 50 degrees, and it's not 50 degrees out. No other codes are set either. I'm not sure what to do next.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
If the LED on the a/c controls is flashing, disconnect and reconnect the battery to clear the trouble code.
Sensor is a thermistor meaning that's it's resistance decreases with heat. Unplugged (infinite resistance) would show something like -32 on your display and if the harness was grounded (no resistance) it would show something north of 100 - so it's not the wiring. You either have a bad sensor or the memory simply needs to be cleared from the Programmer/CCM.
Sensor is a thermistor meaning that's it's resistance decreases with heat. Unplugged (infinite resistance) would show something like -32 on your display and if the harness was grounded (no resistance) it would show something north of 100 - so it's not the wiring. You either have a bad sensor or the memory simply needs to be cleared from the Programmer/CCM.
Advanced
Joined: Apr 2005
Posts: 60
Likes: 0
From: Brighton IL
Thread Starter
Heel & Toe
Joined: Oct 2003
Posts: 15
Likes: 0
From: Columbia City IN
I'm back in business too. Thanks for all the help.
50 is the number you get when the sensor is disconnected. In theory, I'm sure SunCR is right, infinite resistance should display an extremely cold number. But I would guess that the software guys put in a failsafe: if senseless reading, display a "neutral" 50.
I didn't have to drive 45 for 3 minutes (or at all). Soon as I plugged the new sensor in, I was gold. My car is a '91, so maybe this behavior varies with different model years.
My FSM arrived and would have answered the question too. I think the Haynes or Chilton guides are the 3rd best resource. The FSM is the second best. Corvetteforum.com is #1!
Thanks again!
50 is the number you get when the sensor is disconnected. In theory, I'm sure SunCR is right, infinite resistance should display an extremely cold number. But I would guess that the software guys put in a failsafe: if senseless reading, display a "neutral" 50.
I didn't have to drive 45 for 3 minutes (or at all). Soon as I plugged the new sensor in, I was gold. My car is a '91, so maybe this behavior varies with different model years.
My FSM arrived and would have answered the question too. I think the Haynes or Chilton guides are the 3rd best resource. The FSM is the second best. Corvetteforum.com is #1!
Thanks again!
Advanced
Joined: Apr 2005
Posts: 60
Likes: 0
From: Brighton IL
My '90 never moved out of the garage. I did the disconnect, waited about an hour...(mowed the yard)...reconnected and it was good to go.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I guess I'll have to test this...
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I did a test this afternoon. I just started the car and pulled it out of the garage (warm day so I wanted to get a breeze through the cockpit). After about a minute the outside temperature display changed temperature, so that disproves the "refresh" with a certain speed thing.
In thinking about this, I believe the temperature sensor needs to have air flowing over it to get an accurate reading so the car needs to be moving. I have seen my outside temperature reading go way up when the car was parked on warm asphalt on a hot day. It came down right away when I started moving.
Rant, pet peeve: Why doesn't the HVAC controller default to outside temperature like the C5s do? I have always hated that I have to push that button every time I get in the car. I already know what I have the temperature set to, so I don't need to see that. I took the controller apart with the idea of modifying it, but it's a "software switch" that would need some fairly complex circuitry to make it work. I'm an electronic engineer but designing, building and debugging a modification seemed like too much work to me so I left it as is.
In thinking about this, I believe the temperature sensor needs to have air flowing over it to get an accurate reading so the car needs to be moving. I have seen my outside temperature reading go way up when the car was parked on warm asphalt on a hot day. It came down right away when I started moving.
Rant, pet peeve: Why doesn't the HVAC controller default to outside temperature like the C5s do? I have always hated that I have to push that button every time I get in the car. I already know what I have the temperature set to, so I don't need to see that. I took the controller apart with the idea of modifying it, but it's a "software switch" that would need some fairly complex circuitry to make it work. I'm an electronic engineer but designing, building and debugging a modification seemed like too much work to me so I left it as is.
Last edited by Cliff Harris; Jun 17, 2013 at 03:26 AM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I did a test this afternoon. I just started the car and pulled it out of the garage (warm day so I wanted to get a breeze through the cockpit). After about a minute the outside temperature display changed temperature, so that disproves the "refresh" with a certain speed thing.
In thinking about this, I believe the temperature sensor needs to have air flowing over it to get an accurate reading so the car needs to be moving. I have seen my outside temperature reading go way up when the car was parked on warm asphalt on a hot day. It came down right away when I started moving.
Rant, pet peeve: Why doesn't the HVAC controller default to outside temperature like the C5s do? I have always hated that I have to push that button every time I get in the car. I already know what I have the temperature set to, so I don't need to see that. I took the controller apart with the idea of modifying it, but it's a "software switch" that would need some fairly complex circuitry to make it work. I'm an electronic engineer but designing, building and debugging a modification seemed like too much work to me so I left it as is.
In thinking about this, I believe the temperature sensor needs to have air flowing over it to get an accurate reading so the car needs to be moving. I have seen my outside temperature reading go way up when the car was parked on warm asphalt on a hot day. It came down right away when I started moving.
Rant, pet peeve: Why doesn't the HVAC controller default to outside temperature like the C5s do? I have always hated that I have to push that button every time I get in the car. I already know what I have the temperature set to, so I don't need to see that. I took the controller apart with the idea of modifying it, but it's a "software switch" that would need some fairly complex circuitry to make it work. I'm an electronic engineer but designing, building and debugging a modification seemed like too much work to me so I left it as is.
