Disco 2 Using the transmission warning lamp on the dash

Hi, i am currently working on a coolant level warning light and thought about using the transmission lamp as mine is a manual. What would be the best way to tap in? I plan on using a proximity sensor which gives a 0.7v signal when activated

Hi. You have to close the warning lamp's circuit to earth to trigger it(black/green wire in the plug which should be hanging in the oil cooler area unused). You need a NPN and N/C proximity sensor which provides earth when it looses the "target" so it's open when it senses the coolant and closes when the coolant is lost, consider the warning lamp to be the "load" in the diagram as the warning lamp has positive feed one side from the intrument pack with ignition on.... or if you use other kind of sensor which closes on the target you need a N/C relay to direct earth to the lamp through it's contact and coil to be the load... if you dont see what i mean better find somebody who does cos i can't explain better

yes, that is exactly what I have I think i just need to connect the load wire to the green/black wire correct

Maybe yes, IF the sensor is N/C and provides an earth but only in theory as the warning lamp is not actually a "load" cos it's LED so i dont know if the sensor would consider it so, try it and report back if it works, if it doesnt you'll have to use a relay.

Am i correct in thinking that if I connect the green and black wire to an earth, it should switch on the warning lamp? Well i tried it and it did not work, maybe i need to switch the gearbox to auto in the bcu? Although that will have other affects i assume so i wont do that

mad85 said:

Am i correct in thinking that if I connect the green and black wire to an earth, it should switch on the warning lamp? Well i tried it and it did not work, maybe i need to switch the gearbox to auto in the bcu? Although that will have other affects i assume so i wont do that

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Interesting, the warning should come on with bridged wires in the plug, it must be black/green trace wire not green/black... i dont think that the BCU would affect that cos mine is manual too and it comes on for self test and came on when i misconnected the wires at the transfer box instead of CDL warning, can you see the warning when you turn ignition on?

Yes it does come on during self check. Maybe i picked up the wrong green/black wire. Which connector at the bcu should i be looking e as i did not see the plug near the transfer case

That warning lamp is not wired to the BCU, some modells have the wiring above the transfer box others do not, if it's there is single female spade connector on black/(light)green wire. IIRC all of them have the plug(unused on manuals) around the bottom of the radiator on the RH side or beneath the head lamp somewhere, Check the connector views in the electrical library for C0219, and C0686 or you can splice into the wire at C0223 pin 1 , the circuit is BLG(black/light green) wire all the way to the IP

mad85 said:

coolant level warning light

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Hello
Can you share with us the way how you want to check the coolant level? I have tried by installing special sensor and check the level from outside but due to wall thickness of the reservoir tank it did not work.

berg450 said:

Hello
Can you share with us the way how you want to check the coolant level? I have tried by installing special sensor and check the level from outside but due to wall thickness of the reservoir tank it did not work.

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I have bought a proximity sensor like the one in this photo:

It did work but it takes a bit of space in that area that Im currently using for an aux fuse box. So now I ordered another proximity sensor which is a lot smaller, dont have high hopes that it will work to be honest but it will be worth a shot. If it doesnt work I will have to relocate the fuse box to another area

mad85 said:

I have bought a proximity sensor like the one in this photo:

It did work but it takes a bit of space in that area that Im currently using for an aux fuse box. So now I ordered another proximity sensor which is a lot smaller, dont have high hopes that it will work to be honest but it will be worth a shot. If it doesnt work I will have to relocate the fuse box to another area

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Thanks! Did exactly the same. For me the sensor was not sensetive enough to detect tha level stabely. Once it semmed to be working, then it gave false signal.
When I tested the sensor on a normal palsic bottle it worked fine but seems that the wall of the reservoir is too thick.

maybe you mounted it too high and it was splashing a round a bit? this sensor is rated for detection up to 10mm when i tested it , it seemed quite ok, but still need to actually mount it and test it on the road (and off road)

Test it and if it works let me know the sensor type. I have everithing prewired, ready for installation.
Thanks

Can't see the point of a level proxy when caps complete with switch are sourced easily using the principle of a float, magnet and a reed switch

mystery said:

Can't see the point of a level proxy when caps complete with switch are sourced easily using the principle of a float, magnet and a reed switch

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do you have more information or a link for this?

sorry there is a cap https://www.bearmach.com/product/en...enencs/level-coolant-sensor-prc7925r/PRC7925R from the RR Classic that fits up to the 300tdi engines https://www.ebay.co.uk/itm/173477561583 but the later models used a sensor fitted to the expansion tank usually mounted on the bottom which are prone to sinking over time and giving a false alarm. there are top mounting float sensors that can be fitted to the cap that require a hole being drilled in the original cap but avoiding the pressure relief valve area of the cap .there are also side mounting float switches that would require drilling the tank

mystery said:

sorry there is a cap https://www.bearmach.com/product/en...enencs/level-coolant-sensor-prc7925r/PRC7925R from the RR Classic that fits up to the 300tdi engines https://www.ebay.co.uk/itm/173477561583 but the later models used a sensor fitted to the expansion tank usually mounted on the bottom which are prone to sinking over time and giving a false alarm. there are top mounting float sensors that can be fitted to the cap that require a hole being drilled in the original cap but avoiding the pressure relief valve area of the cap .there are also side mounting float switches that would require drilling the tank

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yes, have heard of people complaining about leaks from holes they have drilled into the expansion tank so wanted to avoid that as much as possible, another option is using a coolant tank from an E30 bmw which roughly fits in a disco 2 although i was concerned because the angle of the output port is different so might put unnecessary stress on the coolant hoses in a d2. The capacitance sensor seemed to me as the best non invasive solution

mystery said:

...there are top mounting float sensors that can be fitted to the cap that require a hole being drilled in the original cap but avoiding the pressure relief valve area of the cap

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I can't imagine any way to drill into a D2 cap as to avoid the valve cos it's all over the tank's neck inside ... i have the BMW tank with level sensor fitted and no problem at all, fits like a glove

sierrafery said:

I can't imagine any way to drill into a D2 cap as to avoid the valve cos it's all over the tank's neck inside ... i have the BMW tank with level sensor fitted and no problem at all, fits like a glove

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good to know, did you need to trim the bottom clip/flap in anyway to fit it?

mad85 said:

good to know, did you need to trim the bottom clip/flap in anyway to fit it?

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Nothing at all, simply pushed it in it's place that small difference at the outet port is no factor