Replacing a blade fuse with an MCB; radiator fans.

[Fed_up_Stag-owner]

The 25A fuse for the radiator fans on my TVR 350i has blown destructively, the fuse holder type is:



The fuse holder will need replacing. The reason for the fuse blowing is currently unknown, although the car sat unused for a couple of years, the fans ran for while yesterday with the car idling, and then the fuse blew. The mess that was a fuse probably indicates that it's not just an issue with an old fuse.

In case this turns into a saga of blown fuses and damaged fuse holders, I might fit a minature circuit breaker for easy re-setting, e.g.

https://www.screwfix.com/p/schneider-el ... -mcb/1325p

Any views on fitting an MCB instead of using a blade fuse?

[jenand40]

No, you can’t use those they are 230v.
Do a search on Demon Tweeks for Circuit breaker and you will see the correct 12v ones.

[stevieturbo]

Whilst to some degree some AC and DC components can interchange, and voltages not even that important within their specified range....that would not be suitable either way for a motor of any kind.

Motors will large inrush currents which need to be accounted for.

Really. just buya good quality fuse holder, if need be for a Maxi blade fuse, although at 25A a regular blade like you have should be perfectly fine unless your fans are running for hours .

Ensure good sized wiring, all connections clean and sound etc etc and there should be no problem. Fuses for thatb kind of thing are generally pretty good.

Or you can get circuit breaker style devices to replace blade fuses.

https://uk.rs-online.com/web/p/thermal-breakers/0409889?

[Fed_up_Stag-owner]

Thanks for the replies.

I'd forgotten about motor inrush currents, and I now recall fitting "slow blow" fuses many years ago to small electric motor control circuits (not automotive), these were glass cartridge fuses with a coiled fuse wire inside.



Reading around the subject, the "cost effective" Schneider MCB I linked to is listed as "B" curve for tripping, I probably need a "D" curve to avoid nuisance trips from the motor inrush current

[Fed_up_Stag-owner]

To update this: the connectors to the flying leads for both fan motors were high resistance, wiggle a connector and that fan started, wiggle the other connector and the other fan started as well. Both connectors replaced = reliable fan operation, although needs checking on a run.

The lock-up is a bit damp, which probably doesn't help when a vehicle is stored.

Edit: no fuse holder at the moment, spade connectors onto the terminals of a blade fuse.