Crazy Temp Gauge

[willow]

I noticed on my commute home today that the temp gauge needle on my 325 was behaving very erratically.

It was flicking between half and three quarters
The needle then settled halfway between the half and three quarter, flicking occasionally but never going back down to half where it normally sits, even in traffic jams.

I haven't had any overheating problems before as the head was recently done and the radiator, thermostat renewed. When I got home and looked under the bonnet, the everything appeared fine and it didn't appear to be overheating - coolant wasn't bubbling, hose exiting the rad was cool etc.

I am wondering if this is related to a faulty SI board, as I'm pretty sure mine is on the way out - since I can't reset the service lights at the moment.

Any ideas?

Cheers folks!

[Zayyan]

Mine was doing this a few weeks ago....found out the car had decided to dump all the coolant somewhere!

That probably doesn't help, sorry

[mumpface]

had same problem,was faulty thermostate

[willow]

Mine was doing this a few weeks ago....found out the car had decided to dump all the coolant somewhere!

That probably doesn't help, sorry

Well my coolant level was perfect!

had same problem,was faulty thermostate

I'll replace mine then, but it's only a month or so old Still it could be faulty.

Cheers.

Any more ideas would be appreciated!

[cros]

The temp sensor is used in parallel by the SI board and the guage (meaning the guage looks after itself). The SI board only snoops the signal so it can count down to a service interval sooner the harder you drive a cold engine. However, a bad SI could screw up the sensor signal for the guage depending on how it uses it. I've never followed the path fully.

Probably doesn't apply in this case, but a bad ground through the nut at the back of the guage would make the guage flit around over bumps between stone cold to the correct reading.

[willow]

Thanks Cros, I'll check it out when I replace the SI board.