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I have a Spal Dual 11" Electric fan set up that I have wired with dual 40 amp relays. I have an inline fuse on the power wire to the relays, it's a 32 amp fues and after awhile it blows. Do I need a higher amp fuse or could something else be wrong? Maybe not the right wire quage? I think it's 12 or 14. Thanks

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I don't know how much current your fans pull.

You want to keep the wire as short as possible and use big enough wire. 14 ga would be way too small. 12 ga is nominal.

See if the wire is warm to the touch after the fans run for a minute. If it is, the wire is definitely too small. Try 10 ga. wire, and keep it short.

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The fuse for the "relay" should be small, depends on the current draw for the coil ONLY. The fuse for the "fan" should be between the COMMON post of the relay and the power source. Also, make sure that your GND wires are of the same gauge as your PWR wiring. The relay coil wiring can probably be 14ga or so, probably 10ga for the fan PWR and GND.

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Yes, like the diagram. Post 30 (would be the Common) although since you are powering two fans instead of one, I'd have a fuse between post 30 and PWR source on EACH relay. Again, this is assuming you have two seperate wires off of post 87 going to two seperate fans. These fuses would be rated at 100% of what ever the contact rating is, so according to your post 40A fuses. This will allow for start current on the fan.
 

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The "common" that he's referring to is terminal "30" from Joe's drawing.

Many people refer to "ground" as "common", and it can get confusing. When speaking of a double-throw switch (where the output side has both "normally open" and "normally closed" contacts), "common" is the side of the switch that's common to both output terminals.

edit: I guess we were both typing at the same time. I just wasn't as fast.


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[This message has been edited by cjlandry (edited 08-02-2002).]
 

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Do the fuses blow at start up or while they are up and running? If they survive the start up current ok , then it may be some other problem, like the fuse holder is heating up and helping to blow the fuse. If the holder contacts are not clean or the wire gage is small enough to heat up, then that might be the source of the problem. With the fans running, feel the fuse holder to see if it is heating up.
 

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Are you using one of those white plastic fuse holders with the little red wires? Glass fuses?

If this is the case, you need a completely different type of fuse holder. You can get ATO type fuse holders with heavy enough gauge wiring to handle the load. If you can't find them anywhere else, try a car stereo specialist.

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<BLOCKQUOTE>quote:</font><HR>Originally posted by MarkM:
It's a plastic in-line fuse holder, and when it blows it melts the fuse holder because I can't even open it to replace the fuse.
<HR></BLOCKQUOTE>

Those fuse holders suck, do not use them for anything over Fog Lamp current.


Your loosing the battle at junction points. Use solder, if it's not a crimp contact. Be sure you use the right gauge crimp contacts also. NOt the 20AWG with 4 strands of the 10 AWG wire cut back.



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Mark,
Go to a good autoparts store and ask for an inline MAXI fuse holder with a 30 amp fuse. If your fans are pulling 25 amps, it should be ok. Startup might cause it to blow, if so, try a 40 amp fuse. The MAXI fuse holders have 6 to 8 gauge wires and will handle the fan load (the MAXI fuse holder can use fuses up to 80 amps). The fuse holder you are using is UNDERSIZED for the application.
The other option, and the one I use is to use either 10 gauge wire with a 14 gauge Fuseable Link or 8 gauge wire with a 12 gauge Fuseable Link. This eliminates any bad connections in the fuse holders, since the links are crimped and soldered into the wire. Let me know if I can be of any help.


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I have seen this set up run continous current in excess of 30 amps. The 25 amps rating is at 13vdc and at 0" of h2o. If you put the fan up against the radiator the work load goes up and a rating of .3h2o would be common due to normal restrictions. A unit that I put on a car last year takes upward of 33amps. YOu are running near the edge with the fuse set up that you have.

So, definitely run a breaker....good idea, but run at least a 40amp breaker. Even a 45 would be fine. Typically the breakers will reset after 30 seconds depending on energy amount that tripped it.

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