Coolant Warning Light on Dash

Ratcatcher · Post by **Ratcatcher** » Sat Jun 12, 2021 11:17 pm

Starting to settle down and enjoy the car now after all the work but noticed today the coolant warning lamp doesnt light when i turn the ignition on. Is this normal?

bigwinn · Post by **bigwinn** » Sun Jun 13, 2021 9:51 am

Don’t think mine does- will check

Ratcatcher · Post by **Ratcatcher** » Sun Jun 13, 2021 10:57 am

bigwinn wrote: ↑Sun Jun 13, 2021 9:51 am Don’t think mine does- will check

bigwinn · Post by **bigwinn** » Sun Jun 13, 2021 11:01 am

Ratcatcher wrote: ↑Sun Jun 13, 2021 10:57 am
bigwinn wrote: ↑Sun Jun 13, 2021 9:51 am Don’t think mine does- will check

Deffo- no show at ignition

Ratcatcher · Post by **Ratcatcher** » Sun Jun 13, 2021 11:08 am

Cheers Bigwinn, thats reassuring as i had a water leak when i first picked up the car and was concerned that i wouldnt get a warning if it came back.

But i actually found this today https://www.youtube.com/watch?v=MZY90qwgIEY so i'll check that it works for the belt and braces piece of mind.

Ratcatcher · Post by **Ratcatcher** » Sun Jun 13, 2021 6:17 pm

Ok, all good and the lamp works with the cluster test as described on utube. But, does anyone know how the relevant sensor is activated? I tried depressing the float indicator all the way down thinking that it would be a reed switch of some sort but no light on the cluster unfortunately.

Liam22 · Post by **Liam22** » Mon Jun 14, 2021 12:05 pm

Try disconnecting the water pump - that'll force it on. If you remove the washer reservoir you might be able to get to it from the top.

enuff_zed · Post by **enuff_zed** » Mon Jun 14, 2021 12:28 pm

Liam22 wrote: ↑Mon Jun 14, 2021 12:05 pm Try disconnecting the water pump - that'll force it on. If you remove the washer reservoir you might be able to get to it from the top.

But won't that put the light on for a different reason?
If the OP wants to test the low level sensor works they need to activate that?
Looking at a spare sensor I have, it doesn't work as a plunger type switch, seems to be totally encased in plastic so must work on resistance or something like that?
I guess you could short across the two pins on the plug to prove the wiring works, but not sure how you'd check the actual sensor?

Unless............. does the dashboard light test just test the bulbs or check out the circuits?

pp1600 · Post by **pp1600** » Mon Jun 14, 2021 12:35 pm

Ratcatcher wrote: ↑Sun Jun 13, 2021 6:17 pm Ok, all good and the lamp works with the cluster test as described on utube. But, does anyone know how the relevant sensor is activated? I tried depressing the float indicator all the way down thinking that it would be a reed switch of some sort but no light on the cluster unfortunately.

The sensor IS activated when the float hits the bottom (no coolant)... mine did it last week on ignition and while driving, luckily only a top up was required.

Ive previously replaced the reservoir so i was hoping it hadn't cracked again. A common fault.

enuff_zed · Post by **enuff_zed** » Mon Jun 14, 2021 12:36 pm

pp1600 wrote: ↑Mon Jun 14, 2021 12:35 pm
Ratcatcher wrote: ↑Sun Jun 13, 2021 6:17 pm Ok, all good and the lamp works with the cluster test as described on utube. But, does anyone know how the relevant sensor is activated? I tried depressing the float indicator all the way down thinking that it would be a reed switch of some sort but no light on the cluster unfortunately.
The sensor IS activated when the float hits the bottom (no coolant)... mine did it last week on ignition and while driving, luckily only a top up was required.

Ive previously replaced the reservoir so i was hoping it hadn't cracked again. A common fault.

Hmm, I wonder if the float completes a circuit with the sensor then? Or is it coincidental? Sensor to tell you in the car, and float as a visual check?
Need someone with the light on, to lift the float and see if the light stays on.

enuff_zed · Post by **enuff_zed** » Mon Jun 14, 2021 12:43 pm

Right! This was bugging me, so I enlisted Mr Google.
Apparently there IS a reed switch inside the sensor and it is activated by a magnet on the float.
But you have to keep the two in contact for at least 30 seconds before the light comes on.
Try that.

Ratcatcher · Post by **Ratcatcher** » Mon Jun 14, 2021 6:19 pm

Just got back from the beach/beer/chips/dogs. Great day and there was even a couple of z4's spotted! Thanks for all the info guys, this 30 sec sample time might just be key as im guessing there will be fluctuations in the level during normal service. I'll check tomorrow.

Ratcatcher · Post by **Ratcatcher** » Mon Jun 14, 2021 6:23 pm

Liam22 wrote: ↑Mon Jun 14, 2021 12:05 pm Try disconnecting the water pump - that'll force it on. If you remove the washer reservoir you might be able to get to it from the top.

Im guessing your thinking of electric water pump on the N52? Mines an early 2.5 so belt driven only im afraid.

Ratcatcher · Post by **Ratcatcher** » Mon Jun 21, 2021 9:11 am

Liam22 wrote: ↑Mon Jun 14, 2021 12:05 pm Try disconnecting the water pump - that'll force it on. If you remove the washer reservoir you might be able to get to it from the top.

Bit more experimenting yesterday and you werent actually a million miles from the 'truth' The sensor is NC and when activated it becomes open circuit so merely unplugging it causes the warning light to activate (after around the 30sec as noted above) It would seem i have a knackered sensor or the magnet is missing from the float. Either way, it looks like ill have to drain the system to investigate.

enuff_zed · Post by **enuff_zed** » Mon Jun 21, 2021 9:16 am

Ratcatcher wrote: ↑Mon Jun 21, 2021 9:11 am
Liam22 wrote: ↑Mon Jun 14, 2021 12:05 pm Try disconnecting the water pump - that'll force it on. If you remove the washer reservoir you might be able to get to it from the top.
Bit more experimenting yesterday and you werent actually a million miles from the 'truth' The sensor is NC and when activated it becomes open circuit so merely unplugging it causes the warning light to activate (after around the 30sec as noted above) It would seem i have a knackered sensor or the magnet is missing from the float. Either way, it looks like ill have to drain the system to investigate.

The sensor fits in with a simple twist (bayonet fitting). If you had a replacement to hand and were quick, you could probably replace it without losing much fluid.
Of course, due to the position you have to be in, the fluid you do lose will be into your face, so keep your mouth shut!

If you want to try the spare I have, let me know as I'll be passing your way Tuesday.

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