Brake Fluid Level Warning

[ukkid35]

I have just found out that the wiring to the plug that attaches to the fluid level sensor has been broken, probably for the entire ten years of my ownership

Not only that, but the level sensor in the cap also seems to have failed

Can anyone tell me how the system should work?

[Byker28i]

Only two wires...

[Byker28i]

which is shown top right in the main harness diagram
http://tvr-cerbera.co.uk/WorkshopWiringDiagrams/CE...

or bigger


goes to j7 plug

[ukkid35]

So if you were to remove the cap, with the loom attached, is there a warning on the dash?

Or, of you disconnect the cap from the loom, is there a warning on the dash?

[Byker28i]

No mines not working either, although my handbrake light doesn't work and it's the same light. Something for me to look at.

I took the cap off, tipped it upside down etc and disconnected it...

[sixor8]

As with every other car with the same cap (it's a Ford one I believe), it only completes a circuit (when working) when either the fluid level has dropped sufficiently for the contacts to make, or you can press the yellow cap to test the circuit.

Because of where it is, they often get corroded. I replaced mine on my Cerbera with one from a Ford (Fiesta I think?)

[Byker28i]

Mine doesn't work with pressing the yellow button, nor shorting the wires together, but as said, the handbrake light doesn't work either. I'd assumed it was something from the body off rebuild...

[sixor8]

The handbrake warning circuit should be in parallel and is a switch mounted on the chassis. They often get broken on a body-off; it was on my last Chimaera. I replaced it with a Mini switch, car that is, not the size.

Perhaps the lamp itself is burn out?

None left with this seller if you need a replacement cap, but this is what I bought:

https://www.ebay.co.uk/itm/GENUINE-FORD-KA-FIESTA-...

Edited by sixor8 on Monday 16th August 18:34

[ukkid35]

Thanks - I had no idea the yellow button was for testing

£25 is steep, so I thing I'll try some scrappys first, and take a multi-meter with me

Finding the fault in the wiring is going to be tedious

[sixor8]

They've been around a good 25 years or so on many cars, definitely on Fords. I had one on a '96 Mondeo, it's why the middle of the cap is soft.

Although, having a soft centre, it becomes a weak point, my Cerbera one had a hole in it. Possibly from repeated pressing, but also weather exposure....

The fluid level dropping sufficiently for the float to fall makes the circuit and illuminates the warning lamp. Pressing the cap simulates this, making said cct. If you do not have 12V at either wire with the ignition on, you have a broken wire somewhere. Due to its location, internal corrosion is extremely common.

[Gladers01]

Byker28i said:

Mine doesn't work with pressing the yellow button, nor shorting the wires together, but as said, the handbrake light doesn't work either. I'd assumed it was something from the body off rebuild...

The circuit is looking for an active low 0 volts via SW4 (brake fluid switch) back to J7 pin 14 for the lamp to light, so should work if the wires are bridged at
J20 assuming the bulb is ok, the handbrake similar SW5 back to J7 pin 10, if the light starts to flicker when on the move it's usually a sign the slave cylinder is leaking

[MattPlaneCrank]

I didn’t know about pressing the middle of the cap to test it so I just tried it - works fine! Rare to find something on my car that doesn’t need replacing.

[Jhonno]

MattPlaneCrank said:

I didn’t know about pressing the middle of the cap to test it so I just tried it - works fine! Rare to find something on my car that doesn’t need replacing.

Learn something every day! Will check mine too.