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Astra H Coolant Sensor Fault

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About a year ago my 2005 Astra H threw a fault up with a coolant level fault on the centre (clock) display.

I changed the coolant level sensor in the expansion bottle and the faullt cleared.

The fault has since returned and despite yet another new sensor the fault still remains.

Has anyone experienced a similar problem in their astra? And the solution?

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Air lock in bottom of bottle? Not sure of vaux but had a few probs with clearing bow air blockages in header tank where sensor is.

Can't be much wrong. If you check all the wiring you can see and don't find faulty wiring or connector pin, the only thing left to do is get a read out from your ecu.

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No airlocks. The system has never been refilled since new. The sensor sits in a cavity in the bottom of the expansion tank and does not actually contact the coolant and it is not possible to see inside the tank where the sensor housing is due to a partition.

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We had the same fault in our Zafira, got another switch all was ok. 10 months later same again, I spoke to another Vauxhall specialist and he said its a fault with the switches.

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Can I ask has your astra got air con.

If so check the last fuse on the right hand side of fuse box where your right knee is when sitting in the car.

If this is blown you get a low coolant warning light even though most bottles never had the sensor fitted.

Pls let me know your findings


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My Astra H doesn't have a fuse box at my right knee - the Air-Con works fine and apparently there is a float inside the coolant tank but on the outside of the cavity where the sensor is inserted which gets stuck.

Have ordered a new expansion bottle (£20)an see if that cures the problem.

If the supply wire to the sensor is bridged out that "cures" the problem so the fault lies within the sensor /bottle.

Incidentally I noticed where the expansion bottle is mounted to, it was just hanging on the top rail but is supposed to be on both top and bottom rails.

Will get the new bottle fitted by next Sunday will let you no the outcome.

Edited by steven
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i used to have a vx220 turbo which used the header tank off an astra (can't remember which year/model, although 2005 sounds about right).

as the engine cover was mostly mesh to let heat out, the header tank was exposed to sunlight and they would go brittle and eventually crack/leak and need replacing.


I had exactly the same problem as you describe by fitting a cheapo ebay header tank. on discovering the fault I replaced it for a genuine Vauxhall part and the problem went away, well documented problem on the vx220 owners club.


Hope this helps!

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