Can this be left here for a day or so before its moved to the dead zone please?

I've got a mk2 Focus 1600 petrol as my daily. The speedo and tacho have just started over reading massivley. When the ignition goes off the speedo needle comes to rest at 30mph and the tacho at about 2k. Its just started to overheat too and the coolant looks brown (havent seen it in daylight yet) dont know if thatll be related?

Any ideas? Ive tried the old 'dash unlock' and done the gauge sweep etc but the needles just sweep right round and come back to rest where they were
The dash unlock thing showed running voltage at 13.5v too so its not the battery, temp started to come down when i stuck the blowers on full chat so i suspect the fan switch isnt playing ball or something in the dah isnt telling it to switch

 

Give these guys a try: http://www.ecutesting.com/catalogue/...4048&model=492

 

13.5v sounds a little low. Is it still the original battery? I know the ST's can throw major electrical wobblies when the battery is weak, although not heard of this before. What happens if you disconnect the battery? Do the gauges drop to zero?

 

Not tried that yet Rich, popped the bonnet before and it was fucking hot under there. Coolants gone muddy and theres foam in the header tank. I think either the water pumps fucked or the hg has gone and the heat has baked something and made the cluster go squiffy.
Gonna leave it until tomorrow and then do a comp test on it and disconnect the battery and see what happens.
I shall report back.......

 

Checked this in daylight, cant find my compression tester do couldnt do that. Coolant seems to be the normal reddy/pink colour today. Disconnected the battery and the needles didnt move, but when I reconnected the battery they righted themselves.
Ran the engine up to temp and all seemed well, according to the digi display with the dash 'hack' i ran it to 110 degrees and the fan hadnt kicked in? The temp gauge was showing normal.
Any idea if the temp shown on the digi display is the water temp or not?
Also any idea what temp the main fan should kick in at?

 

Double post

 

It isn't a coolant temp sensor, but a cylinder head temp sensor that just measures the temperature of the head. I would have thought it should have bought the fan on. Does it have a/c? Does the fan come on when you turn it on?