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Heater rheostat - very hot?


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At full on or full off the heater control rheostat is cold but at half fan speed it' gets very hot, to the point of beginning to smell.

I know that it has to dissipate some energy in order to control the fan speed but I've not noticed it getting as hot as this before, too hot to touch. Is this normal?

In fitting some new instrument bulbs, I did knock one of the leads off but there only appears to be possible 2 connections 

Any ideas?

 

Phil

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At fully off there is no current drawn and at fully on there is no resistance in circuit so it will remain cold at these extremes.

The rheostat is supposed to get hot in the intermediate settings which is why the body is ceramic but if it is hotter than normal it might be because the fan motor is partially stalled, perhaps because of a dry bearing, making the current draw higher than normal.  Is the motor turning freely?  

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Thanks Rob

The fan motor has always rattled a bit but it turns freely and chucks out quite a lot of heat. Could be the bearing, as you suggest, I will investigate

Phil

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  • 2 months later...
On 1/9/2020 at 2:11 PM, PhilipB said:

Thanks Rob

The fan motor has always rattled a bit but it turns freely and chucks out quite a lot of heat. Could be the bearing, as you suggest, I will investigate

Phil

It rattled 30 years ago

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