Big deviation in exterior ambient temp display vs actual temp (25+ degrees!)
05-25-2018, 06:04 PM
#1
The Transporter
Thread Starter
Big deviation in exterior ambient temp display vs actual temp (25+ degrees!)
I purchased my car in the winter and didn't notice the temperature differential all that much at the time, but now that we have had several mid-80s-to-90s temperatures I have really been noticing that the read-out on the dash for the current outside ambient temperature is wildly inaccurate.
On average, when the car is getting situated and the sun isn't too intense and it isn't too hot outside, the temperature displays about 6 degrees over when moving and 8 to 9 degrees over when sitting still or in traffic. Today however - and several times in the past week where the temperature has been high and it has been very sunny outside, not a cloud to be seen - the temperature was reading 109 degrees while in traffic; the actual temperature was 84 degrees! This is a 25 degree temperature difference. This was while sitting in traffic; as I started to move and get some speed, it ticked back down until it settled out around 95 or 96 degrees, or 11 to 12 degrees above the actual temperature, while on the highway and moving at my normal "Audi 60" (aka 80mph).
The engine temperature gauge, whether it is warm/hot outside or cold, quickly heats up to the half-way mark between 'L' and 'H'. It does not overheat, nor again tick over the half-way mark. So I figure this must be some kind of sensor that is being cooled down by the movement of the air over and into the vehicle, but the heat of the engine (and my engine gets HOT even though it doesn't come close to over heating according to the engine temperature gauge at least), the beat of the heat from the sun and the surrounding cars while sitting in heavy traffic heats the ambient temp gauge up.
That being said, does anyone have any idea what I may do to fix this? Does that temperature have any bearing at all on any components in the vehicle?
On average, when the car is getting situated and the sun isn't too intense and it isn't too hot outside, the temperature displays about 6 degrees over when moving and 8 to 9 degrees over when sitting still or in traffic. Today however - and several times in the past week where the temperature has been high and it has been very sunny outside, not a cloud to be seen - the temperature was reading 109 degrees while in traffic; the actual temperature was 84 degrees! This is a 25 degree temperature difference. This was while sitting in traffic; as I started to move and get some speed, it ticked back down until it settled out around 95 or 96 degrees, or 11 to 12 degrees above the actual temperature, while on the highway and moving at my normal "Audi 60" (aka 80mph).
The engine temperature gauge, whether it is warm/hot outside or cold, quickly heats up to the half-way mark between 'L' and 'H'. It does not overheat, nor again tick over the half-way mark. So I figure this must be some kind of sensor that is being cooled down by the movement of the air over and into the vehicle, but the heat of the engine (and my engine gets HOT even though it doesn't come close to over heating according to the engine temperature gauge at least), the beat of the heat from the sun and the surrounding cars while sitting in heavy traffic heats the ambient temp gauge up.
That being said, does anyone have any idea what I may do to fix this? Does that temperature have any bearing at all on any components in the vehicle?
05-25-2018, 08:20 PM
#2
AudiWorld Super User
Some sensor variation inevitable given it sits out front (just behind the grille) and is subject to roadway heat, plus vehicle heat if standing. Yours does sound like more than normal for those big deviations. I have only hit those 109 or 110 type numbers when on the road (even in traffic) AND it has definitely been > 100 outside. Just replace the sensor. It plugs into a connector so comes as a piece part. Look around/behind the rings in the grill IIRC, sort of hides in shadows; only a couple inches long. A pain to get to but can just (barely be reached) by wedging some plastic stuff open under hood. Check manual for a better how to.
I don't think sensor does much other than take that reading. Engine air temp will be picked up by MAF, and interior temps and sun load are via various sensors inside. It may affect overall AC function a bit, though refrigerant recharge is the usual long term fix there.
I don't think sensor does much other than take that reading. Engine air temp will be picked up by MAF, and interior temps and sun load are via various sensors inside. It may affect overall AC function a bit, though refrigerant recharge is the usual long term fix there.
Last edited by MP4.2+6.0; 05-25-2018 at 09:37 PM.
05-25-2018, 08:35 PM
#3
AudiWorld Super User
As usual MP is correct. It is located behind the grill and it's not expensive. It is a little difficult to replace. From memory, replacing the sensor has helped some poster cool the interior down faster after the sensor replacement.
05-26-2018, 04:10 AM
#4
AudiWorld Senior Member
Sounds like airflow related
I only have a data based from mine, even in Houston heat and traffic it has only maybe shown a temperature 10 degrees higher than actual. I think your gauge is touching something heated by the radiator. Or your fans are not working.
The engine temperature gauge is purely for looks. Engine temperature over a wide range indicated by the gauge being dead center. Many European cars have this feature.
The fact outside temperature reads normal when the engine is cold and then drifts as the engine warms indicates it is reading actual temp seen by the gauge. Try to figure out why. If cooling fan related you need to sort out.
Run a scan to see if the engine codes can find an issue.
The engine temperature gauge is purely for looks. Engine temperature over a wide range indicated by the gauge being dead center. Many European cars have this feature.
The fact outside temperature reads normal when the engine is cold and then drifts as the engine warms indicates it is reading actual temp seen by the gauge. Try to figure out why. If cooling fan related you need to sort out.
Run a scan to see if the engine codes can find an issue.
Last edited by Panelhead; 05-26-2018 at 04:11 AM. Reason: Spelling
05-26-2018, 06:13 AM
#5
AudiWorld Super User
I'd replace the temp sensor or at least look for damage. It is a delicate part. Mine was damaged when my wife had a little incident a couple years ago. IIRC, in the winter, the temp indicated way colder than normal, like 25°F lower though. A sensor leg broke off from the connector.
Pic from 11:24 pm in Las Vegas (2:24 am EDT on clock) four years ago. Car was heat soaked in a parking garage.
05-26-2018, 06:38 AM
#6
AudiWorld Wiseguy
Not sure what year your car is but if it’s an 04-05 with the two piece grille, its super easy to remove the upper grill to get access to the temp sensor which sits behind. If the fish mouth grill, then removal is a lot more involved and I think is a front bumper pull job.
05-26-2018, 11:37 AM
#7
AudiWorld Super User
You are correct dave, since it is a split gill for an 04 here in the US, it is much easier than the fish mouth grill. My tech did mine without taking the front bumper cover off, but you have to have small hands.:-)
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05-26-2018, 06:24 PM
#8
The Transporter
Thread Starter
Yes it's a 2004; I will see what I can find with the component. Does anyone have a part # so I can look to order a replacement and figure out pricing?
Also in regards to A/C, I have noticed that my A/C does not blow all that cold very often - it's "cold" but not ice cold, and when it's hot outside and with the hot engine radiating in traffic it can get pretty lousy - and it takes a while to get cold. In fact it won't get cold until I am on the road and putting some gas into it. I took one of those 134+ kits with the pressure gauge and noticed that, with max on the gauge was 55, the car was sitting at around 45. I filled it up a quite a bit and the pressure didn't really change. I drove for a while, plugged it in again, and it was sitting near 55. Unplug it, give it a while, and I get near 45 again. I haven't ever had any problems using this refrigerant brand in the past. I don't want to risk over-filling it.
Like I said it does get COLD, but not as cold as I remember several other vehicles getting after a recharge with this same 134+ kit.
Thanks
Naudi
Also in regards to A/C, I have noticed that my A/C does not blow all that cold very often - it's "cold" but not ice cold, and when it's hot outside and with the hot engine radiating in traffic it can get pretty lousy - and it takes a while to get cold. In fact it won't get cold until I am on the road and putting some gas into it. I took one of those 134+ kits with the pressure gauge and noticed that, with max on the gauge was 55, the car was sitting at around 45. I filled it up a quite a bit and the pressure didn't really change. I drove for a while, plugged it in again, and it was sitting near 55. Unplug it, give it a while, and I get near 45 again. I haven't ever had any problems using this refrigerant brand in the past. I don't want to risk over-filling it.
Like I said it does get COLD, but not as cold as I remember several other vehicles getting after a recharge with this same 134+ kit.
Thanks
Naudi
05-27-2018, 11:40 AM
#10
AudiWorld Wiseguy
Yes it's a 2004; I will see what I can find with the component. Does anyone have a part # so I can look to order a replacement and figure out pricing?
Also in regards to A/C, I have noticed that my A/C does not blow all that cold very often - it's "cold" but not ice cold, and when it's hot outside and with the hot engine radiating in traffic it can get pretty lousy - and it takes a while to get cold. In fact it won't get cold until I am on the road and putting some gas into it. I took one of those 134+ kits with the pressure gauge and noticed that, with max on the gauge was 55, the car was sitting at around 45. I filled it up a quite a bit and the pressure didn't really change. I drove for a while, plugged it in again, and it was sitting near 55. Unplug it, give it a while, and I get near 45 again. I haven't ever had any problems using this refrigerant brand in the past. I don't want to risk over-filling it.
Like I said it does get COLD, but not as cold as I remember several other vehicles getting after a recharge with this same 134+ kit.
Thanks
Naudi
Also in regards to A/C, I have noticed that my A/C does not blow all that cold very often - it's "cold" but not ice cold, and when it's hot outside and with the hot engine radiating in traffic it can get pretty lousy - and it takes a while to get cold. In fact it won't get cold until I am on the road and putting some gas into it. I took one of those 134+ kits with the pressure gauge and noticed that, with max on the gauge was 55, the car was sitting at around 45. I filled it up a quite a bit and the pressure didn't really change. I drove for a while, plugged it in again, and it was sitting near 55. Unplug it, give it a while, and I get near 45 again. I haven't ever had any problems using this refrigerant brand in the past. I don't want to risk over-filling it.
Like I said it does get COLD, but not as cold as I remember several other vehicles getting after a recharge with this same 134+ kit.
Thanks
Naudi
