Thermostat or temp sender?

The Doctor

Registered User
Jul 25, 2009
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Hi guys, recently my temp gauge is only reaching 80 degrees and it takes a good 10mins from cold to get there. This has started happening over the past couple of months I guess. Before, it would sit bang on 90 degrees as I would expect. I had the temp sender replaced about 15 months ago which was triggered by a warning on the dash if I remember correctly (I now have the green one) but I'm not sure if this would be the cause of my new problem or maybe it could be the thermostat? Anyone shed some light on this please. Either way I'll probably fix it myself, just want to make sure I'm replacing the correct bit! Thanks.
i had the same problem and i changed my stat yesterday job done..
I would also say its the stat. My S3 did same thing, changed stat and hey presto all sorted :icon_thumright:

Stat and O-ring is around £4

Not sure on the G12 as a mate gave me a bottle.

You may as well get a new dipstick funnel as i can guarantee it will disintegrate as soon as you touch it. They get very brittle over time.

Part No. 06A 103 663 B £3.50 or there abouts.
I had similar issues which were fixed by changing the temp sender. Easy job just make sure the engine is cool before you remove it otherwise your get covered in boiling hot coolant like myself :/
Its a good idea to disconnect the battery as the thermostat is right behind the live connection on the alternator, coming from the battery. Else cover the connection. Audi specialist Abtech fried mine.
Its a good idea to disconnect the battery as the thermostat is right behind the live connection on the alternator, coming from the battery. Else cover the connection. Audi specialist Abtech fried mine.
I'll second this as i fried mine when i did my thermostat :banghead:
Already replaced the diptsick tube last week when I did the PCV simplification/catch can mod. And yes, the old one snapped as I expected it to! Forunately I prevented any bits from dropping into the sump.

Good advice re battery disconnection. Presumably I only need to disconnect one terminal? Only problem is I don't think I have the radio code. Any way I can find this out before disconnecting the battery?
yes just one terminal, you should always disconnect the negative from a battery first (and its always the last to go back on). Covering the alternator terminal could be your other option, plus being extra careful!
-ve terminal is what I thought, given the -ve earth.

Anyone got a thermostat part number please?
Part no from GSF is 931vg0450. £11.46 including vat...
I will be attempting to replace my stat soon, after having the exact same symptoms. I bought the following last night from Audi:

Thermostat - £24
Rubber O-ring - £3
1L G12 coolant - £7.

These are approximate prices (give or take £1), and include VAT.
Just checked. Seems to be a different part number now?

A3 Petrol 9/96 >
The one from euro should be fine but they wont be much more if any from the dealers so it might be worthwhile getting one from them.
I heard they were £24 from the dealers.. which is triple the price, if thats true i'll go non gen, if dealer is close to the £8.99 il get oem
Just go with a good brand.

I got mine from AllGermanParts, was just over a tenner iirc.

A nice rule of thumb is to look at the stat itself, if the manufacturer has bothered to put their name on it, its probably reasonable quality.
It was something like 18 quid when I went to get one last week from the dealer, so I went to a local factor and got one for 4 quid inc VAT. The best tip I can give you for replacing it is to certainly remove the battery negative and also remove the supply lead from the alternator, then you can get a 5mm allen key socket UNDER the thermostat housing and it makes the job a real easy one - took me half an hour including changing the coolant for new G12 stuff
I too got one for £5 from a local motor factor which lasted 2 months so i got another one for £5 from a different motor factor which lasted less than 2 months so i got one from gsf for £13 and its been fine for 6 months maybe i was unlucky but its something to think about.

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