Electrical Problem With Coolant System

[g717xnm]

Hi all,

I have a little problem with the coolant system on my mk1 2.0i with air con (rp4775). I keep getting over heat warnings on the dash. the temp gauge can be at 90 it will light up like a Christmas tree and other time it does not. At high temp, when in traffic it can be fine but other times it can light up like a Christmas tree. It makes no sense. This is why i think it is a faulty ??. The car has had a new water pump, new coolant, new thermostat and a new cap for the water tank. there is no leaks that i can see and the water level in the tank is aways fine. Also i have check that the fans work i see and hear them cut in but I'm not sure if they are run at full speed.

I was thinking of starting at the easiest point and change temp sensor but the one which was sent is different to the one in the car. The one in the car is housed in an aluminum housing which is bolted on to the side of the engine block. In this housing is two pipes one coming in from the bottom and one out from the top. this is carrying the hot water from my engine passed the sensor. There is no brass spanner flats to unscrew it. Can it simply be unscrewed and replace or do i have the buy...find the whole unit?


Any help would be great

Thank
Chris

[noz]

Hi Chris,

Since you seem to have ruled out an actual overheat condition then it sounds like an earthing problem to me. Many of the instruments on the dash will share a common earth with other components. If the earth is not clean somewhere along the line ( i.e. low resistance) then the current trying to return to the battery will get to the common point and, unable to get past the resistance, will then travel backwards through other components trying to find an earth that way. During that process it may well light up other instruments or warning lights on the dash. There's a common earthing point somewhere above the conglomeration of connectors just at your right knee as far as I remember. Under the bonnet there's another two on the near side inner wing, one near the LHM tank and the other down by the battery. There's at least another one on the off-side inner wing. I think I'd clean every earthing point with emery paper and grease well before reassembly if I were you. If nothing else its the cheapest fix and you never know it might just solve your problem.

Let us know how you get on.

Cheers

noz

[g717xnm]

Thank you for that i will have a look.

One thing i should add is the orange thermometer lights up first then the stop light. I have a feeling that something is not communicating correctly somewhere!

Thanks
Chris

This post has been edited by g717xnm on August 04, 2010 03:47 pm