MG TF 2004/2005 OEM Low Coolant Alarm - Wiring diagram, Owners Manual Page

Apologies!! Thanks for pointing out my mistake Roverlike. I'll have another look !

Hi Roverlike,  I've managed to take another look to Identify which SCU unit is fitted to my car. It is , indeed , the later one YWC001541 as can be seen in the attached photo.  Given I have a VIN number 633647 should I be able to get low coolant alarm ? As said previously I attached an expansion tank to the existing socket that had the necessary internal part , waited more than 35 seconds but not red warning light came on the dashboard.  

Your SCU should support low coolant alarm, but your VIN is comming from series of cars which came with wiring but no low coolant alarm sensor. Your car SCU actualy have this low coolant feature disabled because otherwise you would have low coolant light constantly glowing. 

You have 2 possibilities:

1. Ask Paul @  https://www.technozen-electronics.co.uk/  if he can enable it for you but you will need to send SCU to him if he can do it.

2. Contact Philip from PScan here on forum by PM as he said he is willing to add this feature in PScan, but I assume you will need to come with car to him.

Thanks very much for your help Roverlike, much appreciated. I'll speak to my friend to see which option would be easier to do. Is there a link to contact Phil, which poster name does he have in case I need to PM please?
I'm about to install Bruce's alarm but it would be nice to have both low coolant warning systems operating. Belt and braces.
Again , thanks for your help.

Philip is using alias @pscan.uk

That's great , thank you . 

Here is the link to that post:  https://www.the-t-bar.com/forum/9-mgf-tf-pitstop/100545-can-pscan-enable-the-factory-low-coolant-light?start=12#222148  
You can click on the small cloud-like icon below his username to send PM.

Does anyone have experience with whether this will work on new Chinese-made LE500 alarm clocks?

Papaya wrote:

Does anyone have experience with whether this will work on new Chinese-made LE500 alarm clocks?

Wiring diagram for sure is not correct for LE500 because wiring for instrument cluster is different. However LE500 is using BCU, same as older.models. Having that in mind it is important to find out number on the BCU to see if it is the version which supports low coolant alarm.

Hello Roverlike, tonight , after getting in touch with Philip pscan, I my friend and I tried a second time to get the low coolant warning system working.  This time , using a different expansion tank we had success.  We filled the tank with water half way up with the engine running then let the water out. After 35 seconds or so the light illuminated! We then did exactly the same routine with the original expansion tank which again did NOT work. The only difference between the two tanks was that the one which worked was a Chinese made MG part the one which didn't work was an older MG Rover part. 

LancsMGPaul wrote:

Hello Roverlike, tonight , after getting in touch with Philip pscan, I my friend and I tried a second time to get the low coolant warning system working.  This time , using a different expansion tank we had success.  We filled the tank with water half way up with the engine running then let the water out. After 35 seconds or so the light illuminated! We then did exactly the same routine with the original expansion tank which again did NOT work. The only difference between the two tanks was that the one which worked was a Chinese made MG part the one which didn't work was an older MG Rover part. 

In that case it is possible that your older expansion tank lost its metal piece within floating part of header tank. That happenes. This would mean your system works.
However I think that when you put your ignition key in position 2 you do not have your low coolant light check like with other lights on the dash. That part will need to be enabled within your BCU. That way you know that bulb and system is working as it should like othsr checks on the dash.

No I definitely have the check light when the key in in position II. It briefly illuminates in position II and on engine ignition maybe 3 seconds. Then it goes off and last night re - illuminated after 30 seconds when the water in the temporary coolant tank was released .