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

MG TF 2004/2005 OEM Low Coolant Alarm

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In 2004 MG TF came on the market with low coolant alarm fitted. However extremely low information is available on this subject and wiring diagrams were never published. I am trying to fill this gap.

MG TF from VIN RD 632424 to RD 634868 had low coolant alarm wiring fitted but no sensor fitted to expansion tank and therefor you would have checking of low coolant alarm triggered but no sensor - action was needed by T4 to electronically shut down that check.

MG TF from VIN RD 634869 low coolant alarm sensor is fitted as well as adequate wiring to support the function.

Pektron BCU/SCU earlier version YWC001540 do not support the low coolant alarm function. Low coolant alarm was only introduced on Pektron BCU/SCU version YWC001541.



 Owners Manual Page:

 



Low Coolant Alarm Dash Light:

 



Wiring Diagram:

 

 


Connector Details:

 



At some point in 2005 low coolant sensor was no more fitted but wiring is in place.

If you want to get the function of the low coolant alarm, you first need to check which version of Pektron BCU/SCU you have. If you have later version you need to check if you have bulb within instrument panel designated place.
Then you can try to put sensor and connect wiring plug.

If you still do not have low coolant alarm, most probably it needs to be enabled electronically within Pektron BCU/SCU



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That makes sense Roverlike.  My VIN 635066 and has got the alarm setup.  Thanks.

Mine has the alarm. With ignition on the light shows for a few seconds then goes out.
However, I would have expected the light to illuminate if the float is pushed down and it doesn’t.
That doesn’t seem normal. What should I expect?

I have Bruce’s alarm too but at the moment that isn’t sounding either as the level drops.

In case of OEM alarm you will get illumination after 35 seconds when coolant level dropped. That means you need to hold float 35 secomds in order to get light to illuminate. Of course, ignition key needs to be in position 'II'.

in case of Bruce's alarm you need to wait much less with float down.

This delay is there to prevent false alarms when hard cornering or similar situations. 

I had Bruce's alarm fitted to R40 and it has probably saved the engine. 
I have since ordered kits for our older F and the TF.
Fitting one, if you don't already have one is a must do job. 

35 seconds seems a long time if you are on a motorway and a hose splits.

My VIN is 741439 and has a factory fitted low coolant set-up (light on the dash). As it is Apr 2005, that is pretty close to the end of MG-R production.

The OEM sensor has a float which rides up & down over a pillar containing a magnet reed switch; think a foam tyre off a Scalextric car, with a magnet pushed down into it.
The favourite fail mode with these is the magnet dropping out of the “tyre”, you will find it by fishing with a mild steel strip. Getting it back in is another problem, it is doable, I’ve done three.
I can’t remember whether the BCU is expecting an open circuit from the reed to trigger, or a closed.
It was a while ago, I’ve mended a lot of stuff since then.
M

Airportable wrote:

I can’t remember whether the BCU is expecting an open circuit from the reed to trigger, or a closed.

 

BCU is expecting closed circuit to ground from the reed to trigger.

My car is a 2004 but is 629764 so it does not have the wiring for the low coolant alarm. Here is my solution.

I purchased the low coolant alarm kit from B&G. For the warning light, I was lucky to be able to source a late used instrument cluster on ebay that had the low coolant waring light. I switched the low coolant 'icon' to my instrument cluster and mounted the light from the kit behind it. So my instrument cluster now lights up in the appropriate location with the proper icon for the typical four seconds when I start my car. It is very close to a factory version.

One question - did the cars that came with the low coolant light also have an alarm or was it just a light?    

Just the light, no alarm.

Hello Roverlike, I have a 80th anniversary model. I have the necessary wiring with appropriate correct connector as well as the dashboard light. Today a friend let me use a spare coolant expansion tank with a factory fitted sensor that he'd taken off a car. We connected it up to the existing wiring, obviously empty no coolant, with the float pushed to the bottom and ignition in 11 position . We waited well over 35 minutes. Nothing.
Please could you explain what I'd need to do to now make the low coolant warning system work ?