Topic: fan wire melted?

[pioneer4x4]

hey everyone, ive had the 2 speed taurus fan on my xj for about 2 yrs now with no problems, but now it went dead on me, but come to find out the inline fuse i put in between the battery has melted quite severly. my question is when relays fail do they not let current pass through them or could it fail and let all the current go through. i have it set up with a 30 amp relay, i know it needs bigger, so anyway pin 86 goes to ignition hot with on/off toggle between, pin 87 goes to fan +, pin 85 goes to ground, pin 30 goes to battery with inline fuse before battery which is now melted. does anyone see a problem with this wiring except the 30 amp relay? dont know much about relays, im pretty sure it has finally failed and all voltage went straight to my 15 amp fuse, but not sure what happens when relays fail? thanks in advance, anything would be appreciated.

[sharpxmen]

the relay is normally open - if the solenoid fails (which is on a different circuit than the contacts, pins 85/86 on the relay) the relay will stay open and no current will go to the fan. if the contacts fail then you might get some sparks there but that would be just speculation at this point. The only thing i can see wrong is that you have a 15 amp fuse but that should fail before your 30 amp relayif the current is at 20 amps for example. When the relay closes the current will go thru your fuse just like you would have it directly connected to the fan (this is in normal operation, not if the relay fails). If you added some wire on the fuse to beef it up and it held to current over 15 amps then that's why it melted as the wires and contacts on your fuse were made to withstand 15 amps. Not sure what the Taurus fan is rated at, but i would start from there and redesign it if neccessary. The melting can occur if you have a bad connection as well (in the fuse housing). The wiring connections are fine as you described them here, again not sure of the amp draw on the fan and depending on that you might need larger fuse and wires (i have a feeling that it would ne more than 15 amps though)

[jfrabat]

Not sure what the Taurus fan is rated at, but i would start from there and redesign it if neccessary. 

IIRC, the taurus fan pulls around 30~35A in the low speed and about 70A in the high when it starts turning; after that, it goes down quite dramatically.  If you use a controller like Delta Current Control, which controls the speed at which the fan turns, and speeds it up by steps (so the fan does not turn on to the full speed), the amps go down dramatically...

[pioneer4x4]

i dont have the high speed hooked up, just the low one, it runs the ignition is turned on. but im gonna get bigger relay and check all my connections. but i do have one question, everyone always says to use 8 guage wire for the high speed, but the stock wires are all 10 guage? so why use 8 if factory uses 10?

[sharpxmen]

if you have a 15amp fuse and a 30 amp relay your problem is not the relay. now i am not saying a 50 or 85 amp relay would hurt in any way, definitely not but it won't solve your wire melting problem - what wires do you have on your setup today? and if factory is 10gauge and you did not alter the fan wiring in any way it is safe to use 10 gauge. Using thicker wires will not hurt in any way, if you go with a lower rated wire that's when you have problems.

[pioneer4x4]

 i have had all 10 guage wire on it now, but the wire that melted has been soldered together in a few places, so im gonna get a fresh piece of wire,  the fuse was a 20 amp. i know it seems small, but it worked for 2ys or so till now? but my relay was on the other side of engine bay, i think over time it was just getting hot and working loose some connections. im gonna reposition a 75 amp relay closer so i have less resistance. also what kind of inline fuse link are yall using, the one that melted had 12 guage wire, id like thicker guage but havent found anything

[jfrabat]

I run a 40A fure and a 45A relay on my low speed just to be safe...  And the fuse is BIG!  I already melted a small fuse holder once, so I decided to switch (no problems since).

[aw12345]

 I am no fan of the small 70 amp relais, they seem to fail fairly often
Try to find the larger Bosch 60 amp relais they are very reliable
For an inline fuse holder find one for a maxy fuse, those things have much larger spades on them and will handle the current much better.

[pioneer4x4]

yea i was thinkin a slow burn type link would be best, thats what ive got on my alt, probably gonna switch to that style later, for now i rigged up the large type wide blade fuse inline. also puttin in the bosh like u said, but under the name of tyco now..but same relay as far as i can tell. thanks for the replys. let yall know how it works out

[jdarg]

The relay isn't the problem if the fuse melted and the relay is still fine. That said doubling it would be more safe. Anything beyond that is basically overkill.

Too much current through a relay could cause either an open circuit or a permanent closed circuit on the power side. The path could blow into an open circuit, or the contacts could possibly weld themselves into the closed circuit state. They usually go open though...even if the contacts weld, eventually the current breaks the path soon after anyways.

W/out seeing a photo of how it melted, I think the issue isn't so much the rating of the fuse, but you rather may have a really cheap fuse holder.

A 20 amp fuse can take a higher peak current as long as its a quick spike. Though it is small, it does take time for high current to actually heat up the wire and cause a problem depending on how much current it is and the gauge of the weakest point in the contacts.