Temperature gauge woes

W

whuy

Member
Four 4 years now, the temperature gauge follows the same pattern:
- for the first few minutes after a coldstart, nothing happens
- then it climbs, slowly but steadily till it reaches 90°C
- there it stays, rock steady.

Yesterday however, I was driving for quite a while already and happened to notice the temperature read 80°C only, and while I was watching, I saw it drop below 60°C, then start to rise again.
It reached 90°C, but dropped slightly and then wavered between 80° and 90°.
Same thing today (except for the sudden drop below 60°C)

Something's wrong, for sure.. but what?

Werner
2001 1.4 TDI 75
 
It may be the thermostat sticking partially open. I had this problem on a previous Audi where the rubber seat on the stat broke up and wedged it open. Not sure if the A2 stat is the same design but it could be something similar.
 
Yes, either that or the ventilator sensor failed. Whatever it was - it's gone, the gauge functions as before. Strange.

Werner
2001 1.4 TDI 75
 
whuy said:
Four 4 years now, the temperature gauge follows the same pattern:
- for the first few minutes after a coldstart, nothing happens
- then it climbs, slowly but steadily till it reaches 90°C
- there it stays, rock steady.

Yesterday however, I was driving for quite a while already and happened to notice the temperature read 80°C only, and while I was watching, I saw it drop below 60°C, then start to rise again.
It reached 90°C, but dropped slightly and then wavered between 80° and 90°.
Same thing today (except for the sudden drop below 60°C)

Something's wrong, for sure.. but what?

Werner
2001 1.4 TDI 75
Click to expand...

It´s the termostat.

If it was a sensor the car probably would get a trouble code since it would got to rich Air Fuel Ratio.

easy to change yourself!
 
This one takes me back...

I had identical symptoms on my first A2, a 1.4 petrol, whilst under warranty.

One of the Audi On Call mobile mechanics immediately diagnosed a faulty temperature sender. It's the device that transmits the coolant temperature at the engine cylinder head to the gauge.

I recall the technician saying the fault wasn't uncommon - he'd seen it on a few A4's. A replacement took minutes to fit - a simple swap and top-up of coolant lost when the defective component was removed.

Hope this helps.

Regards

Ian - 2004 tdi90 se
 
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Our FSI temp guage was going occasionally to 0 for a few minutes and then up again, sometimes to 60 then off and then finally back to 90.

Audi replaced the temperature sender and its been fine since.
 
orustturbo said:
It´s the termostat.

If it was a sensor the car probably would get a trouble code since it would got to rich Air Fuel Ratio.

easy to change yourself!
Click to expand...

Really? How? Where is it located?
 
Well had the car maintained (3rd VSI, 150000km/93000mi), and a few extra's:
- brake fluid service
- brake pads (front, first replacement!)
- temp sensor and thermostat replaced
all for 640 EUR, or 430 GBP at today's rates. Pretty good.
 
My temperature gauge started playing up this week - up to 90 then suddenly down to 60, then back again to 90. There were no warning lights suggesting this was not an electrical fault so I decided to replace the thermostat (£12 with seal)
This involved disconnecting the battery, removal of the belt tensioner and alternator and draining off some of the coolant. You are supposed to be able to wind the tensioner back against its stop and lock it in position with a special pin but it was impossible to do without a very long 16mm offset ring spanner (no room for a socket) I ended up easing the tensioner back with a short ring key and slipping the alternator belt off before unbolting it. This was easy enough to do but made refitting the alternator belt rather tricky.
After starting the job I found out the botton rad hose is now a 'push fit' with an O-ring seal and retained with a clip. Whatever happened to rubber hose and jubilee clips!!! I did not have a replacement O-ring and had to drain the coolant via the oil cooler hoses. On removal, the old thermostat looked ok so I checked the opening and closing temps in a pan of water on the stove - and it worked fine. Now convinced I had wasted my time, I fitted the new part and put everything back together- then went to open the boot to connect the battery - and found it had locked. Also found the keys don't work the central locking with no power on. Luckily all the doors remained open and I managed to fold the back seats forward and get to the battery from inside the car.
Amazingly, when I drove the 20 mile to work today, the temp gauge worked perfectly. Hopefylly this is no fluke or the next installment will be about replacing the temperature sender unit.

http://www.a2oc.net/forum/attachment.php?attachmentid=12620&d=1372893323

Cheers Spike
 
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Replacing the thermostat did not fix the wandering temperature gauge. Stage 2 was to swap the temp sender unit located on the gearbox end of the cyl block. It seals with an O.ring and is a push fit in the housing, held in with a plastic U.clip. It's possible to replace it without draining the coolant but the location makes this rather tricky - I lost about 1/2 litre of anti freeze in the process - but that was not the worst bit. While trying to replace the U clip I dropped it down the back of the gearbox. Without the clip you can't start the engine as the sender will just blow out with the water pressure. Frantic searching and the use of a 'bottle brush' to sweep out every nook and cranny finally dislodged it. For the second attempt, I looped some thin string round the clip before clicking it into place - it was not going to escape a second time. All that was left to do was remove the string and top up the header tank. After over 100 miles the gauge is still working perfectly.
Before starting this job, I was 80% certain it was the thermostat. It cost me a wasted £12 and 1/2 a days work so unless the symptoms are 100% I would go for the temp sender first. It cost approx £25 plus an hour to fit - providing you dont loose the clip.
Tip of the day - spend an extra 50p and buy a spare clip before you start the job.

Cheers Spike
 
Temp sender

Wish I'd read your post earlier. Replaced stat 4 months ago, seemed OK for about a week then gauge stayed at zero again. Replaced temp sender now and fine. Heard that original ones were green - faulty from day one virtually - but replacements are green; funnily enough my old one was green so, after 34,000 miles, am I on the 3rd sender?...oh and the G12 plus antifreeze isn't that cheap when you always end up washing the street in it, what a great design!
 
i think i have a similar problem
Temp gauge gets to normal 90, then 10 miles into journey, going down a hill, the over temp light comes on.
The gauge however still reads normal.
I assume this is the temp sender unit.
Any ideas of current price?
thanks
glen
 
The sensor is ~22€
But normaly there is no warning signal.
If it is the yellow lamp, it is not enough water in the system.
 
spike said:
Replacing the thermostat did not fix the wandering temperature gauge. Stage 2 was to swap the temp sender unit located on the gearbox end of the cyl block. It seals with an O.ring and is a push fit in the housing, held in with a plastic U.clip. It's possible to replace it without draining the coolant but the location makes this rather tricky
Click to expand...

I have a faulty temperature gauge too and I am looking at replacing it myself. Would it be possible to get some pictures of the location of the temp sender unit. I can then use your description and atempt to replace it.

Cheers

Yatin
 
Hi Yatin
Sorry, I did not take any photos of the temp sender location at the time. It's located in a housing at the back of the cyl block (front is where the belts are) and points towards the bulkhead. The plastic body of the sensor was green on my 2001 TDi. Hope this helps

Cheers Spike
 
sender or thermostat?

I have the same symptoms on 2001 tdi - sometimes reads 90 sometimes 60 and readings in between at random.

Based on advice, went for sensor replacement 1st.

I had a black 2 pin sensor (269415 06-01) and following a lot of searching and 3 visits to Audi dealer worked out that the listed replacement part 059 919 501A (4pin) is an upgrade. This wouldn't fit straight on however owing to incompatible 2 existing connector 1J0 973 702. After a lot of hassle, I worked out you also need new connector 4B0 973 712 and wire 000 979 131 plus shrink wrap. You cut off the old connector and use the wire to solder connect. I connected the other to pins numbered 1 (white/grey wire) & 2 (green/grey wire) on the 4 pin connector. Hope this helps anyone on the same route.

However! … on testing, the gauge still sometimes reads 90 sometimes 60 and readings in between at random.

I am now therefore considering replacing the thermostat as it seems both items give the same symptoms when they play up.
 
Spike thanks again brilliant thread and two great stories will let you know how we get on, but not able to look at it till Friday due to work.
will probably go for the sensor first thanks again.
 
Did a search and found this thread. This evening I had something similar happen. Temp was at 90 as normal, but after switching the aircon to recycled air for a few minutes while driving past a particularly ripe sewage works(!) it seemed to drop to about 80. I switched heat off completely but it never really came back up to 90 again. On the way back home I kept an eye on it and it didn't reach 90 at all, hovering just above 80 (with the air con off).

I'm going to keep an eye on it, but does this sound like a temp sensor or something?

Cheers, Jon
 
Hi Jon
Ref posts 9 & 10 of this thread, I'd say its an 80% chance the temp sender is on its way out

Cheers Spike
 
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