Coolant level light... always on...

Post Tue Dec 10, 2013 7:39 pm

Right - not that important, just bugging me a bit - I'm sure I saw a thread about this recently, but can't find it anywhere!!!!!!

M20 engine (2.7) touring, coolant level light in the overhead check panel is always on!!!!
Has been like it for a long time!!!

I checked the sensor in the top of the coolant tank and it didn't look good, so I replaced it with a new part from BMW - but the light remains!!!

Electrical connector on it looks ok, so is there a way to test this???
What should I see where???

The cable from it dissapears downwards - where does it go???

All ideas/suggestions welcome!!!

Post Tue Dec 10, 2013 7:55 pm

One side of the plug loom goes to the earthing point on the inner wing, just below the expansion tank. A bit of corrosion here will give you a bad earth, and correspondingly a bad sensor signal.

Post Tue Dec 10, 2013 9:08 pm

The coolant level sensor used on an E30 M20 fits into the reservoir from the top, but on most models it fits in from the bottom. If you are supplied with the wrong one (like I have been on a couple of occasions), you will find that it puts the light on when the coolant level is OK, but keeps it off when the level is low.
You can check the circuit by fitting a piece of wire between the two pins in the socket so as to short circuit them together. This should keep the light off.

Post Tue Dec 10, 2013 9:31 pm

I recently had this and fitted a new level sender. The light was still on but after a closer inspection I found that one of the wires had broken just before the plug! Worth a look!

Post Tue Dec 10, 2013 11:16 pm

I'll give these a check then - hoping it's not the wrong part - I've had so many wrong parts recently it's driving me nuts!!!

Connections/wires looked ok at a brief look, but I didn't see where it earthed!!!
I'll try the short cct first so I know which way to go!!!

Ta!!!

Post Wed Dec 11, 2013 12:19 am

miniblob wrote: Connections/wires looked ok at a brief look, but I didn't see where it earthed!!!

Earthing point is inside the cabin, behind the glove box, IIRC, or it could be on the LH inner wing, but there's unlikely to be a problem there.
The wire breaks just where it enters the moulded part of the plug, and although the copper is broken completely, part of the outer sheath still hangs onto the plug, preventing the wire from becoming completely detached.

Post Wed Dec 11, 2013 1:36 am

I'll give it a close inspection then!!!
Cheers!!!

Post Wed Dec 11, 2013 5:42 pm

Brianmoooore wrote:
miniblob wrote: Connections/wires looked ok at a brief look, but I didn't see where it earthed!!!
Earthing point is inside the cabin, behind the glove box, IIRC, or it could be on the LH inner wing, but there's unlikely to be a problem there.
The wire breaks just where it enters the moulded part of the plug, and although the copper is broken completely, part of the outer sheath still hangs onto the plug, preventing the wire from becoming completely detached.

This exactly what happened with mine! It would be so easy to miss.