Have just been scouring Ford Forums, and found a couple of guys who had the problem with the oil guage creeping into orange and sounding the buzzer when hot at idle/traffic lights. All have posted that they fixed the problem by adding an extra earth strap to the engine.

http://www.fordforums.com/showthread.php?t=16031 for more info

But what a bugger - Just yesterday I swapped it for the on/off switch type to test - might swap it back and add the strap instead and se what happens.

yup this is the fix for the au's as well


extra earth from -ve of batter to block and also to alt

So what do they consider an acceptable voltage potential across earths?

I measured 0.35 volts from body to engine (same from Body to battery), but only 0.07 from engine to battery. Thats with lights and fans on (with AC max)

Got some nice cable from work, so i'll make some links from engine to alternator and body.

So far the pressure switch hasn't beeped at me, so good news so far!

no idea on the potential...

but a nice fat 4 gauge eareth strap from the engine to the chassis is a good idea as well!

If this is the true cause then I would also expect that the other engine sensors that reference to earth, namely the O2 sensor and IAT would also be reading incorrectly, causing poor performance / economy issues.
Cheers
TW.

Just in case anyone was curious...

Fitted the earth strap (1AWG!!) from body to engine earth. It cured my voltage drop from those two points, but my oil pressure problem remained.

Went and fitted a T-piece and oil pressure switch. Wired up the switch to the blanked off oil light in the cluster (So I now have oil gujage with guage light AND regular oil pressure idiot light on the bottom.

Got the car nice and hot, but it still beeped low oil warning at me - at the same time, the new low oil switch light flashed at me as well. Pretty much eradicated any electrical problems.

So, I've changed from 20W50 to Penrite HPR 15W60 - all seems good so far. Car was nice and hot, and guage stayed above the orange - measured 2.2 bar minimum in diagnostic mode.

Hopefully this is a permanent cure. Just waiting for my lifters to have a whinge now

Nice easy fix!

Nice easy fix!