My DC Fan wont spin fully, Only stutters and stops every 5 seconds

[JackBoy]

worth a try.

I have bought the one Richard mentioned, will post an update back once I tested it.

Although I now see another problem - if I was to stop the fan and try to restart it before the NTC has cooled down, a too high current maybe allowed to pass through it resulting in the fan not spinning again... are there any common ways to get around this?

 

[static zap]

Fans definitely take a large surge at start up,
(very likely to vary a little between units )
Stick with a big safety margin and will still be working in 3-5
years when componenets have aged .
A dedicated timed startup circuit ,
resistor ,thyristor ,relay + electronics .
(bulb + relay ..cheap and dirty)
Is a workaround to hot thermistor -restart problem!

 

[Richard Burns]

I have bought the one Richard mentioned, will post an update back once I tested it.

Although I now see another problem - if I was to stop the fan and try to restart it before the NTC has cooled down, a too high current maybe allowed to pass through it resulting in the fan not spinning again... are there any common ways to get around this?

Usually there is an arrangement whereby the NTC resistor is taken out of circuit after it has performed its start up function, to employ this method would probably exceed the cost differential of the PSUs.
If you were manually present then you could install a make before break switch to take the NTC out of circuit after a second or two, perhaps you could activate a relay on a RC delay that provides a lower resistance path so that the NTC will cool somewhat as a cheapish alternative.
If the NTC is well ventilated then it should cool quickly and at least provide some resistance, since the 20A PSU could cope then the 15A must be close to not tripping so even a lower resistance than 10Ω may be enough to stop the overload operating. However the residual heat would only be a problem if the fan were switched on again quickly after stopping.