Spotlight Inline Fuse Melted

Well today i replaced my old original spotlights that came with my 2006 TD42i (IPF i believe and bloody good one's) as the chrome ring around the outside and the mounting bolts were rusted and just about buggered so i replaced them with a new set 2 x 100w Narva spotlights, same size wattage as the originals.
I waited patiently all day so i could test them at night time and bugger me they lasted about 30 seconds and popped the 30amp fuse from the battery, so after searching around for a spare fuse i only found a 25amp so i fitted that and that lasted about the same time only this time it popped just before a complete meltdown.
The wiring is 4mm from the battery to the original Nissan relay and down to the lights and is only a couple of years old as it was replaced when i got a new steel roo bar, but the original relay was not enclosed, just screwed to the firewall (sideways) and i noticed the terminals are turning a nice shade of green due to exposure i guess.
Apart from fitting the wrong size fuse...duh, (the original 30amp worked fine for years) but popped almost straight away with the new lights would a relay in such poor condition cause more electrical draw and contribute to the fuse overheating or is there a bigger issue lurking elsewhere in the wiring and how can i test the draw on the new lights to see exactly what is going on
Thanks for any help
Time for another beer i guess.

I take it they are 100 watt globes.
Retrace your wires sounds like you have a short somewhere
100 watts is only pulling 8.3 amps

As TD says there may be other issues, but yes corroded terminals may cause a high current draw and it is also a possibility that you have some current flowing through the "crud" to earth. I would suggest a new relay with new spots anyway as it's been there a while. Clean up all terminals and check for shorts and bad earths and try again. If it still gives trouble try it one spot at a time - always could be a faulty spotlight or internal connection.

Plus with the IPF's grab some wet and dry and go get them powder coated.
Thats if the reflector is still ok, easy enough to buy new bolts too.
I would have thought 4mm was a tad small ,Ive always used 6mm
for any power wire.

Yes they are brand new 100w my son brought for himself and never fitted as he got a good deal on some Great White LED spotties and fitted those instead.
So if a 100w light only pulls 8.3 amps x 2 = 17 tops, not enough to melt a 25 amp fuse so it looks like i need to visit Mach One in the morning for a new relay and probably some 6mm wire as well AND check each light individually for any issues, you just assume new lights are good to go.

Well guys thanks a lot for the info as it gives me something to start with.

Just thinking there may be a problem inside the lights

Well guys i checked the lights and they were good, found some wiring done by the people who installed my Ironman roo bar a bit suspect and replaced that and then decided to replace all their wiring to the spotlights and dumped the original corroded Nissan relay and replaced it with two 30amp relays from Mach 1 as i forgot about the two 30watt driving lights fitted inside the roobar which all worked fine before changing the spotties and running only one relay so i didn't really find the problem, but installing two relays and replacing all the wiring to the spotties certainly fixed whatever it was, but now i am getting a nice collection of aftermarket relays sitting under the bonnet that need a permanent home instead of being stuffed into whatever space is available and looking very messy so if anyone has any idea's about some way of mounting them in a box or whatever to protect them and get them away of exposure etc let me know.

I've seen ppl use small tupperware style containers to waterproof different bits and pieces.

I use these for all my additional relays, they fit together and look quite neat
http://www.ebay.com.au/itm/Relay-Mou...QAAOSweW5U5soL

You can get them preterminated if you wish