Over heating/ dodgy temp reading

[Eddypunch]

Hi, my e30 320i 1989 auto 101k miles.. is overheating on tick over but ok'ish when driving it's just over the middle mark. Well, That's when the needle is not going from hot to normal (just over middle). I'm thinking it could be a clogged rad? And clueless about the electrics

[Brianmoooore]

Is it overheating? It's normal for the temperature to increase slightly when the car isn't moving, and for hot coolant to travel further down the radiator. The heat from the centre of the radiator then bends the bi metallic strip in the viscous fan coupling, causing the coupling to lock up and drive the fan.
The scale on the temperature gauge isn't linear. The centre section only covers a few degrees, and it's only when the needle gets to the red that the temperature is definitely too high.
If it is overheating, then the most likely cause is a failed viscous coupling, although a rad. that is blocked near its centre can fail to operate the viscous coupling.
No electrics involved in any of this!

[Eddypunch]

Thanks! It's only overheated on tick over once, never when driving.. yeah it's just hard to tell when the needle is going up n down. I'm going to check the rad and thermostat see if there's any change

[Brianmoooore]

If the needle is constantly jumping between its normal position and another point about a sixth of the scale higher, then the problem is likely to be a loose small brass nut on the back of the instrument cluster.

[Eddypunch]

Thanks! Do I need to be taking the instrument cluster off?

[Brianmoooore]

You do, if that's what the needle is doing.
There's a few other things that should be done to it while its out as well - check soldering of 220 ohm resistor, check SI board batteries, check fuel gauge brass nut and replace blackened or blown bulbs, including those on the SI indicator board.

[HartgeH27]

Good post Brian.