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[tcs]

Hi,

I have just staretd getting an erroneous "coolant level" display on my V reg 2.0 Omega estate (X20XEV engine).

Wiring across the sensor plug removes the alarm. Wiggling the wires around the plug seems to have no effect, i.e. they seem sound. The float floats fine - right up to the top - and when it does you get a connection on the sensor pins. I have played around with this extensively and can't find any suspect connections and the float is as free as a bird.

But - I still an alarm.  What am I missing? Does the alarm need some kind of reset?

Any ideas gratefully received.

Regards.

[Jimbob]

these go faulty every now and again, sounds like youve ruled everything out, so its new header tank time, at about £35 new.

[fiend61]

and a plus to the new header tank is they look nice aswell    nice and clean and you can see the red antifreeze   

[tcs]

Well, I know it's "only £35" but that's quite a few bottles of Theakstons when I haven't been able to prove where the fault lies.  I think I need to tap into the wiring while it's all assembled to see what's going on. (One of the bug-bears of being a test engineer - just can't give up that easily)

[Andy B]

Well, I know it's "only £35" but that's quite a few bottles of Theakstons when I haven't been able to prove where the fault lies.   ..........

it's the float switch that's goosed. trust us!  You only need to bridge the connector underneath the header tank for a day or two to prove it all, if it doesn't give low coolant then you've proved that it's the header tank

............ but we all know that now 

[TheBoy]

Short out cable under the bottle to prove.

Also, check if float sticky due to poor coolant servicing in its life.

[Jimbob]

yup, unplug sensor, use a paperclip as 'replacement sensor' and you will have proved the fault 

[tcs]

But this is what's bugging me - I have done everything suggested by everyone:

Shorted across the plug - alarm goes away.
Checked the float - as free as a bird (fairly new coolant as well).
Put a meter across the sensor while filling the bottle with water - switch closes once the float starts to rise.
No corrosion at all at the plug - almost looks new.

Given that this is effectively a 2 part problem and both parts appear to have been eliminated it is a bit frustrating.

However, I might just have to take your advice and splash out on a new bottle - then stay sober for a week or two 

Thanks for all the advice. Let's consider this closed and I'll try to remember to let you know the outcome.

Regards.

[Chris_H]

I've had two expansion tanks on mine , the second one bought used.  Buzzed out ok but failed pretty soon after.  They must be reed switches and I suspect go too high impedance or something.  I wondered about slapping a transistor in there  but settled for the shorting link.

[Agemo]

TCS Where are you? There may be a breaker who has one for loan/sale. 

[tcs]

I guess the chances are that a used tank will suffer the same problem very soon.

The comment from Chris_H seems very likely. It is obviously a reed relay and I guess it's quite possible that even a fairly low resistance will cause the alarm to trigger, depending on the circuit used.

If I have a worse job to do this weekend which I would like to avoid then I might take some accurate readings and have a play with a parallel resistor - just for fun.  Sure beats cleaning up the garden. 

[tcs]

OK, I gave in and got a new bottle.

I ripped open the old bottle because I had reached the conclusion that the magnet had seperated from the float but it hadn't - rock solid. So I remain totally baffled but with a new bottle. Ah! well - next problem?

[smurfdjman]

hi guys, how do you short the sensor? and will this make the coolant level warning disappear?

[Jimbob]

hi guys, how do you short the sensor? and will this make the coolant level warning disappear?

unplug the socket from the bottom of the bottle.
Insert paperclip into socket
warning gone 

[Andy B]

hi guys, how do you short the sensor? and will this make the coolant level warning disappear?

unplug the socket from the bottom of the bottle.
Insert paperclip into socket
warning gone 

If you're just using a paperclip I'd suggest using insulating tape around it, or use a  bit of sheathed wire