Coolant fluid level light - won't go off...??

[Wally Dog]

Hi chaps,

Just a quickie - I had the red light on the dash for the coolant level but level was good. Swapped over the header tank for one from the scrappie that looks almost spanking new, theory being that the sender in the header was FUBAR - but - now it's swapped over, the light is still on!?! It could be that the new(ish) header tank has an identical problem with the sender or it could be a wiring issue.

Anyone had a similar episode?

Many cheers,

WD

[JUDGENINJA]

Potentially a wiring issue to the ECU ??

[Wally Dog]

Fek

[Dangerous Dave]

Have you tested the sensor/wiring in some way?

[M-R-P]

I'd check the wiring harness mate, as far through as possible, possible a damaged bit of wire or dirty connection somewhere.

[Dangerous Dave]

AFAIK when the coolant level drops the sensor is activated, so if you unplug the level sensor the light should go out. If it doesn't then it would point to a wiring problem/short

[Wally Dog]

Right - un-plug the sensor and the light does go out, so I think that rules out a short in the wiring up to that point, as it would stay on if there was a short. Plug it back in again and the light comes back on, despite the level being absolutely fine.

Think it must be a recurrance of the same issue I had with the old sender unit, as the part was 2nd hand. Worth a punt for £9!!

[Dangerous Dave]

Cool, so wiring problem ruled out :)
So its either the sensor or the float/magnet is stuck in both the tanks. If you shake the old tank, you should be able to hear it rattling.

[Wally Dog]

Yup - they both rattled and I thoroughly cleaned the new header tank before fitting with vinegar and flushed through with water. As far as I can see, the float is up where it should be, not stuck down at the bottom of its' little slot.

Still a bit befuzzled! You mentioned a magnet...?

[Dangerous Dave]

The float will contain a magnet so when the coolant level drops the sensor is activated by the magnet.

So it sounds like the sensor is §§§§§§ed.

[Wally Dog]

Cheers all - agreed, new sensor is around £10 from Volvo but it looks like it could be an ar$e to fit! Anyone done one?

[Dangerous Dave]

Its easy mate, the sensor pops out the bottom of the tank (no clips, just plastic lugs holding it in), there will be no leakage as the tank is moulded to fit the sensor in without it touching the coolant (if that makes sense).