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1988 110 standard condition - except the fuse holder looks to be a later type from 300 Tdi (blade fuses rather than the earlier glass cartridge type).

The fuse to my heater fan has not blown however the plastic casing has obviously got hot and started to melt. My only thoughts are it could be caused by a bad connection to the fuse or it is rated too high (15 Amp currently fitted). There is no sign of burning or melting on the wires to the heater motor. Does anyone know what would cause this? It is the only fuse with this problem. 

I have replaced the fuse and all is working fine, but I don't want a fire!

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Bad crimp on the wire, loose fuse holder, cheap fuse, corrosion.

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Thanks both. I think it qualifies as all of the above. The fuse is certainly loose in the holder and I know previous owners have been chopping about with the wiring over the past 31 years, it is a cheap fuse from a well known national chain  motoring (slowly turning into a camping) shop and yes there is corrosion. 

I think you have given me plenty to go on and accelerated once again my plans for the re-wire!

Thanks:i-m_so_happy:

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Sounds like just stripping the wire back & re-crimping fresh terminals on might do the trick - a loose and corroded connection will heat up nicely!

I used FBB8U fuse holders from VWP when I re-did mine (also 1988):

http://fuddymuckers.co.uk/wiki/doku.php?id=alfie:fusebox_upgrade

It's a bit tight as you crimp a standard spade on & then connect that to the fusebox, but it came out nicely.

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If the fuse is loose then that's where I would start. I purchased a pack of blade fuses and found that the blades were very thin and did not fit well at all, I tightened it by bending one blade slightly to the right and the othe to the left which made them fit tighter but in the end I purchased fuses that were far better quality  The fuse 'sockets' are hard to clean up, an electrical contact cleaner spray helps but doesn't always gets rid of corrosion or the tarnish, fuse blades and the sockets are usually silver plated and loose their connectivity due to tarnish, this is evident when you see the blades of fuses having a black coating, a little metal polish or Tcut on a bit of cloth will clean them up. As for the sockets, a very fine, thin wet and dry paper folded over and poked in and out a few times cleans them up.

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Thanks for this. I will get round to the re-wire at some point in 2019 as the electrical problems I am coming up against are getting more frequent. In the mean time I am going to solder in a new terminal as the old one is corroded and loose, I will also get some (of what I hope) better quality fuses from Autosparks.

 

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You can always tell the difference between the good and not so good blade fuses, the blades are thinner and the plastic housing is thinner as well and paler in their rating identification colour also, often the rating marked on the better quality fuses is picked out in white, on the poorer ones it's not and the rating is harder to see. Avoid fuses that come in a pack with the name Blackspar.

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So far I have nothing to compare them with. I don't know who makes the fusesI have. They are packed in the said shop's own brand.

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The best fuses and relays come from cars at the scrapyard as they would've been decent quality form the factory.

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That's pretty normal behaviour for a fuse which is too low rated, not too high.

When I measured a standard Defender fan motor in the snail housing it was running around 13A at full chat. That's more than enough to make a 15A fuse run hot.

I don't know if thats a typical current or not, but if it is, the fuse should be at least 20A rated. Baseline recommendation from the manufacturer is to run fuses at no more than 70% of rated current for continuous operation at 25C.

The fuses also dissipate heat into the holder and wiring, so even if the contacts are good, cheap fuseholders and small wiring often cause fuses to run hotter than necessary.

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thanks for the additional pointers.

I think the original spec says 15 Amp for the blower motor, I am reluctant to stick in a higher rated fuse from a safety point of view. I will address the poor connection first.

I understand the logic behind the second hand fuses from a scrap yard and I my 110 has many parts sourced from my local LR scrap yard in Glastonbury BUT how do I know if the fuses I scavenge from a used vehicle are original and surely I must be able to buy good fuses from somewhere?

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Posted (edited)

You can generally tell if the fuses are decent quality, just by the look and feel. If they look like they came out of a christmas cracker, they probably did.

There will be others, but a couple of options easily found :-

Multicomp are decent quality, and they have a built in LED to light up when blown.

https://uk.farnell.com/c/circuit-protection/fuses-fuse-accessories?ost=fuse+ato&searchref=searchlookahead&product-range=ato-series

Littelfuse probably as good as it gets.

https://www.mouser.co.uk/Littelfuse/Automotive-Fuses/ATO-Series/_/N-1z0zlhtZba8b5Z1yzxjo9

 

As always, a smear of vaseline on the fuse legs will work wonders to keep moisture out of the contact area for years.

Edited by TSD
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I would advise not to smear anything on the contact points of a fuse as you are introducing a barrier that will restrict current, it's like smearing your battery connections with vaseline, smear it on after you connect the leads to keep out moisture and corrosion, not before. If you want to work out what rating fuse you should use in any circuit, (and cable rating) devide the Wattage by the Voltage which gives you Amps.

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Vaseline is used in countless millions of telecoms connections, if it weren't suitable for smearing all over connections, they wouldn't do it!

 

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1 hour ago, Farmerfred said:

I would advise not to smear anything on the contact points of a fuse as you are introducing a barrier that will restrict current, it's like smearing your battery connections with vaseline, smear it on after you connect the leads to keep out moisture and corrosion, not before. If you want to work out what rating fuse you should use in any circuit, (and cable rating) devide the Wattage by the Voltage which gives you Amps.

Vaseline flows away from the points of contact,  and fills the interstices in the metal surface. It forms an airtight, watertight seal around the point of connection, preventing or greatly inhibiting corrosion. It's fine or your battery connections in the same way unless you get carried away and put pints of the stuff on.

Once you have calculate the current as you explained, you should then consider the initial switch on current draw versus time, the fuse manufacturers specifications for I2t, and in this case the manufacturers recommendation that for an ATO fuse, at 25degC, fuses should be operated at no more than 75% of rated current for continuous operation. The second link is quite useful if you really want to understand.


ATO Fuse datasheet

Littelfuse Application Guide

 

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2 hours ago, Bowie69 said:

Vaseline is used in countless millions of telecoms connections, if it weren't suitable for smearing all over connections, they wouldn't do it!

If you buy telecom splice connectors from 3M you have to specify if you don't want them vaseline-filled. Likewise telecom cables are often vaseline-filled.

The entire UK phone network (well, the copper bits) is basically smeared with vaseline - ask me how I know ;)

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It seems that our copper phone wires have never had this treatment, the lines are so degregated that when it rains they fill with water and we loose our connection, BT/Openreach have known this for the last 8 years and won't fix it. But that's another story!

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1 hour ago, Farmerfred said:

It seems that our copper phone wires have never had this treatment, the lines are so degregated that when it rains they fill with water and we loose our connection, BT/Openreach have known this for the last 8 years and won't fix it. But that's another story!

Likely one or more of your connections is an old block of screw terminals up a pole or similar and it's likely been there since the dawn of time. Not every connection is jellied but most are.

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