Engine coolant temp and fan speed

[MalcolmSu]

Coolant temp and fan running

I changed the water coolant temperature sensor at the weekend. I changed it because the dashboard gauge would drop from 90c to 60c (zero) of its own accord as I was driving along. Equally it would rise quickly back to 90c a few minutes later. I'm pretty certain the actual engine temperature was not reflecting this.

Before I changed the sensor the gauge very consistently measured 90c.

With the new sensor the gauge rises to about half way between the dot after 60c and 90c - about 80c?

Tonight on my drive home I put the air con into diagnostic mode measured the engine temperature. It quickly rose to 75c and stuck there plus or minus a degree for my whole commute (35 miles).

So I don't think I've anything to worry about?

Except I've now noticed the fan is running full speed when driving and is still running for a full 5-6 minutes after I've stopped the car.

I can't say I've paid too much attention to it before but I don't think this is 'normal'. Is there something I need to do after replacing the sensor to 'reset' the the fan? Or do I have another separate issue?

[MalcolmSu]

Just been out and stuck the car on VCDS. Initially I did an autoscan and the only fault that came up was;

1 Fault Found:
16500 - Engine Coolant Temp. Sensor (G62): Implausible Signal
P0116 - 008 - Implausible Signal - Intermittent
Readiness: 0000 0000

The car had cooled down since my run home so i set VCDS to do a live monitor or whatever it's called. I sat and watched the engine temp rise slowly as the car warmed up. It then got to about 70c and then suddenly jumped to 143c and surprise surprise the fan kicked in full speed. Yet the air con temp was only showing 72c?! Here's the latest error...

1 Fault Found:
16501 - Engine Coolant Temp. Sensor (G62): Signal too Low
P0117 - 001 - Upper Limit Exceeded

So what's up - have i got a duff temp sensor? Have I installed it incorrectly?

[Shoppinit]

Duff sensor. Bad luck. If you bought it from Audi / TPS then they'll change it for you and throw in the labour.

[Shoppinit]

Or maybe your electrical contacts need cleaning?

[posterboyj]

Sounds like the thermostat....

[Shoppinit]

Not if it jumps 70° in a second.

[MalcolmSu]

Thanks Shop, it came from Poland via eBay. Another lesson learned.

Out of interest where is diagnostic code 34 on the air con taking it's temp from then? It's a very steady 74°c once the engine warms up...

[Shoppinit]

There are 2 temp sensors in the sender. One sends its info to the aircon, the other to the ECU. Can't remember which one goes to the instrument cluster.

[MalcolmSu]

Based on my experience it would seem if dash and air con are fed from the same info. Picked a new sensor this morning from Glasgow Audi. Now £40 lighter.

[MalcolmSu]

Coming home the other night in heavy rain with fans going full blast and headlights on there was hardly enough power to drag the windscreen wipers across the screen so I decided I couldn't wait until the weekend to change the coolant temp sensor.

Managed it this time in around 35-40 minutes although I did have to take a quick trip to Audi to buy another circlip as I broke the other one putting it in (53p plus VAT btw).

Pleased to report all is now well on the temperature sensing and fan front.

However another problem has occurred and I'm not sure if it's related?

When I started the engine after fixing the temp sensor the orange triangle with the circular arrow around it was on. I did a quick VCSD scan and got these two faults;

Address 02: Auto Trans Labels: 01V-927-156.LBL
1 Fault Found:
18265 - Load Signal: Error Message from ECU
P1857 - 35-00 - -

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4B0-614-517.LBL
1 Fault Found:
18265 - Load Signal: Error Message from ECU
P1857 - 35-00 - -

Any ideas - is this something i've done whilst fixing the temp sensor? Dislodged something? Or just not related at all?

[Shoppinit]

Clear it and see if it comes back. Your ECU has sent a dodgy value to the trans and abs. Might just be a glitch.

[Russellj80]

Yeah clear it and see if it comes back. Heavy rain/damp weather can do funny things to cars!

Ps. Do you have a pic of where the temperature sender is located?? .. Always handy to know these things.

[MalcolmSu]

Ps. Do you have a pic of where the temperature sender is located?? .. Always handy to know these things.

Here you go --> http://www.flickr.com/photos/surgenor/8 ... hotostream

[Russellj80]

Good job mate!! .. That one little picture saves so much grief lol [THUMBS UP SIGN]

[Mr Footlong]

[THUMBS UP SIGN]

The n00b is strong in this one