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Coolant temp gauge not working, but OBD tool can read the temperature realtime.


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No.

The temp sensor has two output readings, one for the dials, one for the ECU. You can drive your car fine with a temperature sensor that has a working reading to ECU but broken to the dials. When it's the other way round, you'll know about it ;)

If it bothers you (mine was like that for ages, never bothered me) then replace it, will cost about £15.

Edited by Skezza
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No.

The temp sensor has two output readings, one for the dials, one for the ECU. You can drive your car fine with a temperature sensor that has a working reading to ECU but broken to the dials. When it's the other way round, you'll know about it ;)

If it bothers you (mine was like that for ages, never bothered me) then replace it, will cost about £15.

Cheers mate! Just out of interest what would happen if it is completly cut off from the ECU aswell? Can I assume it would constantly idle at high RPM?

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Cheers mate! Just out of interest what would happen if it is completly cut off from the ECU aswell? Can I assume it would constantly idle at high RPM?

Well, assuming it fails in the usual way, it will give off no reading whatsoever to the ECU, so it will constantly see the engine as cold. To compensate, it will run a rich mixture, all the time, because there will be no change in the readings. There may be an increase in revs (couldn't tell you for sure as I've not had one go on me yet), but I assume the engine performs fine when you start it early in the morning, then as you get up to normal operating temperature, it will begin to feel sluggish due to overfueling, and then start cutting out. You might even struggle to start it again after it's warmed up.

If I was you, I'd eventually change it but don't break your back to do it. If your Lupo is running fine right now then there's nothing to worry about. Just because one part has failed doesn't mean the other part will. It's also a very common issue on VW's around that era and it seems in most cases the sender to the dials packs up while the sender to the ECU remains working. When I got my first Lupo back in 2007, it didn't read anything to the temperature dial. I got it fixed... last year, as in over 4 years after I got it lol, and to be honest, I only got it fixed because the coolant level sensor packed up which meant I had absolutely no reading to the dash if something went badly wrong with my coolant. Upon being told it would cost a minimum £70 to fix the coolant level sensor due to it being submerged within the tank, I removed the connector plug, arc'd the two connections using a piece of thin plastic coated wire, plugged it back using a piece of thin tape to stop it sliding back out (got me through an MOT like that) which turned the light off on the dashboard and had the temperature sensor replaced for £15 :)

Cushty

Edited by Skezza
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What if the temperature gauge works intermittently? Is that likely to be the sensor too? I guess so. For £15 I should get it sorted!

Ultimately, for 15 quid, it's a pretty cheap fix, but I don't think it's one that is urgently required... unless of course the sensor to the ECU has gone which I suggest you change it immediately lol.

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