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Old 19th September 2019, 20:26   #1
freck
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Rover 75 CDT Connie Tourer

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Default Coolant temp sensor fault.

Hi folks, haven’t been here for a while as my tourer (diesel) has been laid up unused for some time (surplus to requirements )
Unfortunately, my wife’s car was stolen a couple of weeks ago so the tourer is needed once again and I’m in the process of getting it roadworthy again.

Thankfully, with a fully charged battery she’s up and running again, however, I’ve got the fault of the cooling fan running constantly, including for 3 minutes after ignition off.

I’ve checked the test menu and found that the coolant temp sensor is faulty and giving a reading of -128 deg, so have bought a new one and connected it up but I’m still getting the same reading.
Now I haven’t yet fitted the new sensor into the head, could this be the problem? Does the sensor need to be fitted to create the -ve/earth path to work properly? I’ve tried just holding the body of the sensor against the engine but it still doesn’t read.

Any advice or info is greatly appreciated
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Steve
Teamwork makes the dream work!

Mods planned - Cruise retrofit - Done, ZT front bumper - Done, 160 remap - Done...and probably one or two more


This vehicle was the 15,751st 75 Tourer to run off the production line, out of 27,407
This vehicle was the 3,726th 75 Tourer CDT Connoisseur to be made out of 4,100
This vehicle was the 732nd 75 Tourer in Starlight Silver (code: MBB) to be made out of 4,100 Starlight Silver 75 Tourers

Last edited by freck; 19th September 2019 at 20:29..
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Old 20th September 2019, 08:33   #2
T-Cut
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My initial thoughts.
Coolant temperature sensors are pretty bulletproof.

The ambient temperature reading (-128) suggests that the sensor signal isn't getting to the ECU, which controls fan operation. If the ECU doesn't know the coolant temperature, it 'assumes a worst case scenario' and activates the high speed fan to cool a potentially overheating engine. This will run for several miutes after ignition off.

I'd start by checking the sensor connection. Give it a good clean up and work backwards from there if necessary.

If that doesn't resolve it, there may be an unrelated issue with the fan controller board.

TC
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Old 20th September 2019, 15:05   #3
freck
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Default

Thanks T-Cut, I’d sussed that out from doing some searching of the forums and found a post from Marinabrian saying he’d found it out the hard way!

Anyway, just to update, today I’ve fitted the new temp sensor and there’s no change, so I then disconnected the ECU and belled back to the sensor and it seems the wiring and connection to the sensor are all fine, giving a reading of ~2600ohms through the sensor.
Seems you were right about them being bulletproof T-Cut as the old and new sensors are pretty much the same readings.
This is leading me to think it’s an ECU fault, so I’ve emailed BigRuss to see what he can do for me.
Fingers crossed!
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Steve
Teamwork makes the dream work!

Mods planned - Cruise retrofit - Done, ZT front bumper - Done, 160 remap - Done...and probably one or two more


This vehicle was the 15,751st 75 Tourer to run off the production line, out of 27,407
This vehicle was the 3,726th 75 Tourer CDT Connoisseur to be made out of 4,100
This vehicle was the 732nd 75 Tourer in Starlight Silver (code: MBB) to be made out of 4,100 Starlight Silver 75 Tourers
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Old 20th September 2019, 15:33   #4
COLVERT
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Been laid up for a while you say.

Water in the plenum chamber while not in use.--
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Old 20th September 2019, 17:27   #5
freck
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Quote:
Originally Posted by COLVERT View Post
Been laid up for a while you say.

Water in the plenum chamber while not in use.--
No, the plenums are bone dry and clear. I’ve always kept on top of this during the time I’ve had it.
The car’s only done 53K miles and the ECU looks like new to be honest.
__________________
Steve
Teamwork makes the dream work!

Mods planned - Cruise retrofit - Done, ZT front bumper - Done, 160 remap - Done...and probably one or two more


This vehicle was the 15,751st 75 Tourer to run off the production line, out of 27,407
This vehicle was the 3,726th 75 Tourer CDT Connoisseur to be made out of 4,100
This vehicle was the 732nd 75 Tourer in Starlight Silver (code: MBB) to be made out of 4,100 Starlight Silver 75 Tourers
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Old 27th September 2019, 18:51   #6
freck
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Rover 75 CDT Connie Tourer

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Location: Preston
Posts: 1,051
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Thanked 274 Times in 226 Posts
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Well unfortunately it looks like the car’s going to end up being scrapped.
I was going to get her back on the road again for the Mrs to use but she’s been out and bought a brand new Beemer so the tourer is now surplus to requirements.

It’s such a shame seeing as it’s only done 53K miles but for me it’s not economical to spend any money on it that I’d never see back, even if anyone wanted to buy it.

So that’s another one gone folks.
__________________
Steve
Teamwork makes the dream work!

Mods planned - Cruise retrofit - Done, ZT front bumper - Done, 160 remap - Done...and probably one or two more


This vehicle was the 15,751st 75 Tourer to run off the production line, out of 27,407
This vehicle was the 3,726th 75 Tourer CDT Connoisseur to be made out of 4,100
This vehicle was the 732nd 75 Tourer in Starlight Silver (code: MBB) to be made out of 4,100 Starlight Silver 75 Tourers
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