dipsticks Posted January 13, 2019 Share Posted January 13, 2019 Whilst changing batteries last week I came across 3 fuses that seem to have cooked themselves in a strange way. The attached picture shows how the fuses in question seem to have overheated blowing up the plastic around the top of the blades within the plastic. I can't understand why the plastic around the middle portion, which I thought was the thinnest portion setting the fuse value has'nt blown out as well. As far as I can tell the seating sockets in the receptacle/fuse holders are good and tight and I'm fairly confident that the current passing through is well below the fuse value of 25A in this case. I just can't work it out, any answers advice much appreciated. Link to comment Share on other sites More sharing options...
Alanb Posted January 13, 2019 Share Posted January 13, 2019 Prompted by what seems to be thermal discolouring of the RH blade of pictured fuse, may I venture the suggestion that the fuseholder could be the cause of the problem. Heat would travel through the blades which are in close proximity to the plastic. The fusible element section would have worse thermal conductivity, and does have greater separation from the plastic. However my MH was originally equipped with 40A blade fuses for starter and habitation battery connections. I was not aware of any overheating problems prior to upgrading to maxi blade fuses. Alan Link to comment Share on other sites More sharing options...
Charles Posted January 13, 2019 Share Posted January 13, 2019 Strange. If you're right about the spades being tight in the holders it can only be cheap fuses. Perhaps the metal spades are impure or have a resistive coating on them (which would cause a small voltage drop volts x amps =Watts 8-) and of course heat). The fact 3 fuses are the same it does point towards cheap fuses too. Link to comment Share on other sites More sharing options...
dipsticks Posted January 14, 2019 Author Share Posted January 14, 2019 Thanks very much Alanb and Charles. Alanb, thanks, my photo is at fault and I struggle to reduce them to less than 100kb. Both the blades are actually shiny and bright so the discolouring is just an error of the picture. You are correct……….I just studied the fuse in question with a magnifying glass and the plastic around the fuse element does not touch it so has not been subjected to the heat created that surely must have blown the plastic at the top of the blades. Charles, thanks, I think you have ‘Hit the fuse on the head’ to coin a phrase. I had no idea that there were both quality and cheap fuses though thinking about it now it’s obvious and makes sense. I now recall (it was quite a while ago) I purchased the holders myself to protect my modifications and they were good quality (I believe) however a neighbour, who had sold his Motorhome gave me a box of assorted rating fuses, so I just used them 4 or 5 of them I believe. I have just compared them with an original Ford fitted fuse under a magnifying glass and as you rightly say they are definitely ‘cheap’ the stamping out of the blades is rubbish and the plastic moulding looks tatty. I’m not sure of the metal material of the blades of the Ford (could be copper or brass) but the cheap ones are aluminium for sure. So I think that’s the answer I’ll order some quality fuses and keep some as spares too, I found a company that sell OEM fuses as used on new vehicles. Thanks again to Alanb and Charles for answering my question, I’m wiser now and hopefully this thread may help someone else in future. Link to comment Share on other sites More sharing options...
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