Temp Guage

[Woz]

Hi All

Could anyone tell me if it is possible to short out the block connector for the water temp sender, just to see if the guage is working ,ie on older cars you were able to short out the connector and the guage would read maximum. But they were only two pin connections where as mine has four.
I have replaced the sender unit but the guage still does not register any temp. When the ignition is turned on the needle moves very slightly about 2mm from its off position.
Any hints or tips would be appreiciated.

Cheers

Woz

[akaax]

i have exactly the same problem with my temp gauge, have you found the problem or a cure yet? let us know, cheers.

[DarthVader911]

I have same problem,

Checked water temp with VAGCOM and it displays correct water temp, but gauge temp stays below 60 or reaches 90 and then drops again.

[ini]

If you have the older 'blue' square type you should be OK, but there a few different versions (temp ranges) of the newer 'green' D shaped type, and they all look the same.

2 pins for ECU, 2 pins for instruments.

If you are driving a TDI, the temp will only reach 90 on a run, around town you will not reach operating temp.

[DarthVader911]

Thanks ,

I have 2.6 12V Avant, so it reaches normal operating temp of 90Deg normal driving.

Does the color of the plug corolate with the color of the sensor ? Or do I need to remove plug to see which sensor I have ?

[bowley68]

I recently bought a 99 A4 Avant 1.9TDI. Having same trouble with temp gauge, moves a couple of mm to 60 when I start up and then doesnt move exept when it just decides to randomly go to 90 which I assume is correct, it stays there for a while sometimes a few minutes then goes back to 60. Hoping its just the sensor.

[PaulF99]

I have a 1999 Avant TDi (AVG), and I, too, have been wondering about the displayed temp.

My gauge spends most of its time around 75, but moves up to 90 when crawling in traffic, or stationary. It never spends much time in-between 75 and 90, just moves from one to the other depending on conditions.

What is considered normal?

[DarthVader911]

Now that u mention that, I've never seen mine anywhere between or over 90

Maybe Audi engineers are very clever and they have the perfect cooling system.

[AutoTDI]

If you are driving a TDI, the temp will only reach 90 on a run, around town you will not reach operating temp.
I have a 97YM 1.9TDI(110). The temp does reach 90 around town and stays up there on a run. On a very hot day, with the A/C on, the temp will exceed 90. However, on slowing down after a run, the temp will then drop below 90 for a while, before coming up again. This is my theory concerning what's happening:
There are two cooling fans, one mechanical, viscous coupled and the other electrically driven. I have noticed that the electric fan only operates sporadically, probably when "on a run" and the engine is being thrashed. When the car then slows down, with both fans whirring away, the cooling then becomes ultra-efficient until the temp drops someway below 90 when the thermostat cuts out on the electric fan and the temp then creeps up to 90 again. I reckon the electric thermostat must be cutting in at about 95 and out at about 80.
There are actually three different thermostats working together here; there's the mechanical thermostat that controls the flow of coolant to the radiator, the viscous coupled fan and the one controlling the electric fan. I suppose all sorts of things could happen if/when any of these thermostats change their characteristics. The main thing is that coolant temp should hover somewhere around the middle of the dial.

[Woz]

i have exactly the same problem with my temp gauge, have you found the problem or a cure yet? let us know, cheers.

Hi akaax

Still no information I'm afraid, waiting for someone to reply to my thread. The correct sensor is fitted as I gave Audi my chassis number and they supplied the sensor. We'll just have to be patient. . . . . .

Woz

[PaulF99]

I've found out a bit more info about the temp gauge on my car which might be useful for people.

The gauge is not directly displaying the actual coolant temperature it seems - there is a computer in the way.

On my car (late 1999 A4 Avant auto) when the car is cold and started up, the gauge will initially display the actual coolant temp. I confirmed this by monitoring channel 49 of th e CCU diagnostic display while the car was warming up. The CCU and gauge match exactly - impressive.

When the actual coolant temperature gets to 80C, however, the gauge suddenly jumps to 90C and stays there. I guess it is trying to tell you that is has reached the lower end of the acceptable running temperature range.

Maybe it sticks at 90C until the car starts overheating and then the gauge goes higher to signal the overheat condition? I have no way of checking this though, as I have discovered I must have a duff thermostat, since I can't get the actual coolant above 78-77C during normal driving (ie my gauge never says 90C). I have to stop and run the car on fast idle for 5-10 mins to get it above 77C.

Another interesting effect I found while doing this experiment was that when the actual coolant temp reaches 89C, the engine revs will jump up about 100rpm while holding a constant throttle position. Maybe the ECU is switching to different operating conditions at this temp? In which case, I'm never reaching it :mad:

[edihans]

My A4 (2001, 2.0 petrol) initially showed symptoms that the temperature needle would randomly fall back to 50, then to come back to normal (90 degrees). Over time (few months) things got worse, and it never indicated anything anymore. Last weekend I changed the green temperature sensor (pn 059 919 5014) for a new one, and now I do get a reading from the gauge. :)

However, only when driving start-stop in town, it gets up to 90. On the motorway it indicates around 60 only (in 10 degrees outside weather). I questioned this on another thread (http://www.vwaudiforum.co.uk/forum/showthread.php?p=95887) and the general conclusion is that the thermostat is gone. Seems not uncommon for 6-7 year old A4's; I must be unlucky that it happened with my '01 A4 :mad:

Before this all happened, regardless of motorway or in-town driving, it would always be solid on 90 degrees within 1-2 minutes after a cold start.

[PaulF99]

Well, I replaced the thermostat and coolant last week and my gauge now shows 90C all the time. The actual coolant temp (as shown by CCU channel 49), varies between 89-92C.

Looks like my old thermostat was sort of working, but at the wrong temp (77C),

[Bigdom71]

I have an issue with mine. It's a 2001 on a 51 plate.

I've had it for a couple of weeks now, comes with FSH part dealer, part independent specialist (83k).

Some times the gauge will work and sit at 90c once warm, other times it doesn't move at all for the entire journey (this can be in excess of 100miles). Yesterday night for some reason it was holding approx 94c.

Do you think this indicates the sensor requires changing?

[edihans]

Do you think this indicates the sensor requires changing?

Looking at the sympthoms it seems faulty. It will be the sensor sitting in between the battery and cylinder block. You can see the sensor but it's slighty hidden under a big airpipe. This pipe is easy to remove (just 2 clips).

My new senser didn't include the U-shape clip which holds it in place so it took me 45 min to find it back after it fell down on the enginedrip tray after I wiggled it out! Don't drop that clip! I paid around £20 for the sensor from Eurocarparts.

[rhencullen1989]

Hi, i also have an issue with the temp gauge on my 1.8T, but because the gauge does move slightly (approx 2mm) i am putting my bets on a fully stuck open thermostat. If the sender for the gauge was at fault i don't think the gauge would move at all. I have just bought a new gauge £5 from febi) and am going to change it this weekend, i am also going to flush my cooling system through because i believe it has the wrong antifreeze in it. It should have the G12+ which is red or pink in colour, mine is blue!!this could be the reason for the (hopefully) stuck open gauge. I will re-post if it all works ok. This is also the cheaper option from changing the sensor (but a bit more involved).

[a4cam]

Well, I replaced the thermostat and coolant last week and my gauge now shows 90C all the time. The actual coolant temp (as shown by CCU channel 49), varies between 89-92C.

Looks like my old thermostat was sort of working, but at the wrong temp (77C),


99 times out of 100 , it will be the thermostat , it has a limited life . Usual signs that it has cacked itself are the engine fails to reach operating temp , but you will usually find that the temp may rise to the correct temp if the car is left stationary for a while with the engine running . Due top the fact there is no air flowing through the radiator to cool it down .
Hope this may have been some help to you