Coolant warning light

[Tom93]

Since my rod fitting/engine build, i have the red coolant light on the dis with three beeps everytime i turn the ignition on, hot or cold... I didnt have this problem before. Now the only thing ive changed in relation to the cooling system is the header tank because mine was all yellow... Now i have vcds so i checked engine module and instruments for faults and all clear so i messaged the seller telling him i think its the header tank and got this reply...


Hello - the sensor is connected to the brain so if it is faulty you will get a fault code, I suspect it is something else wrong as the sensor will either give a reading or not and if it doesn't you will get a fault code, I can also confirm we have never had any of these faulty.

Any shed of truth to this or ********?

 

[<tuffty/>]

Faulty sensor in the tank assuming that the fluid level is correct as it is lower when cold than hot...

<tuffty/>

 

[Tom93]

Ok heres a weird one, fitted a brand new genuine header tank light still comes on.... Plenty of water in there, no temp issues at all, heats upto 90 and stays there all the time dafuq?

 

[<tuffty/>]

Why is that a problem?

If you are monitoring the coolant temp via VCDS and its getting to 96degrees but the gauge stills indicates 90 then this is normal... its designed to prevent people panicking while the engine temps are in operating range... 96/97 is where the fans kick in on slow speed... just over 100 degrees and the high speed kicks in... if it doesn't go down quickly enough or continues to rise then the gauge will start to rise too and eventually you will get an overtemp alarm

<tuffty/>

 

[Tom93]

The problem is the red flashing coolant light on the dis all the time and the three loud beeps everytime i turn on the ignition...

 

[<tuffty/>]

Hummm... and its defo at the right level in the tank on cold?

Only other thing I can think of is wiring... could be a break in the wire... the sensor works by using the resistance of the coolant to determine level... when coolant is low then the sensor probes are exposed causing an open circuit.... if there is a break in the wire somewhere then it will see this as an open circuit all the time

<tuffty/>

 

[Tom93]

My thoughts exactly, would both pins go to the ECU, or one pin will be signal/power and the other to ground? I did probe the plug with my meter and got ground on one pin but nothing on the other, but without a wiring diagram i wouldnt really know what to expect anyway. Also checked for fault codes and that was all clear.

 

[<tuffty/>]

I believe its wired to the dash not the ECU as this is part of the function of the DIS

Chances are the break is fairly local to the plug as this is its harshest environment...

Maybe worth trying to trace the wires as far back as you can and replace from there... the main part of the loom is pretty resilient so its more likely just in the run from the main part of the loom to the plug (don't discount corrosion of the plug either)

<tuffty/>

 

[Tom93]

Had a look, couldnt see anything obvious...



Except that coppery thing hanging out the back of the plug :/ hmm

Aaanyway, repaired and all working for now.

 

[<tuffty/>]

Cool

<tuffty/>