Rad Fan Fuse Keeps Melting - Page 2
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  1. #11
    Exceeded sell by date Plumpcars's Avatar
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    Isn't it fan startup that causes most current draw rather than when running so that's where you need to check most. As has been said a tight fan or even a corroded/poor connection can cause problems. Some of the American fan systems use 40A fuses because they draw so much.

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    Quote Originally Posted by Plumpcars View Post
    Isn't it fan startup that causes most current draw rather than when running so that's where you need to check most. As has been said a tight fan or even a corroded/poor connection can cause problems. Some of the American fan systems use 40A fuses because they draw so much.
    Yes,
    The single US made fan on my truck draws 30A on startup, and 20A running, so maybe there isn't a fault on the twin fans themselves. It could be just that the pair use more than 30A when running. Perhaps individual circuits with two fuses and two relays might be the answer if there isn't any fault apparent with the fan motors.
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  4. #13
    Exceeded sell by date Plumpcars's Avatar
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    Stu I agree. When I've used twin fans I've always used twin relays and fuses as well. Also gives some blow rather than none if a fan fails as the two are unlikely to fail together.

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    Off the Xmas card list kapri's Avatar
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    Don't twin fans usually work seperately ? ie they are usually one for normal use and the other cuts in when aircon on ? So, as said above, they need seperate relays and fuses if yuo have them cutting in together.

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    Official RnS Addict UK RUSS 1960 OLDS's Avatar
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    Hi Curnie,

    I think you have probably got your answers amongst the posts that have already gone up.

    Generally twin fans will have two circuits, ie one feed, one switch, one relay and one fuse per circuit. The difference is normaly the switches become live at different tempreatures for example one may be set for 85 degrees and the other for 95 degrees. In the case of air con there is a third circuit employed which would bypass the tempreature switches and put both fans on together regardless of engine tempreature, as to get maximum cooling effect you need maximum amount of air flow.

    As "stueeee" and "plumpcars" say two seperate circuits is the best way to go,, as a fault on one circuit should have no impact on the other circuit.

    As you say the fuses are melting i would guess the fans are drawing close on the 30 Amps hence they are getting hot and starting to melt things before popping where if they were to draw say 40 Amps they would just blow the fuse immediately (so no melting of things).

    Not teaching you how to suck eggs, but the relays are only designed to carry x amount of current (amps) so you need the right one for the application you are using it for. Heated rear window or heated seat relays are designed for carrying quite a high ampage (will still vary from car to car though).

    Cheers.

    Russ.

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    Administrator blackpopracing's Avatar
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    Most relays will have their rating written on them. Average will be 30 amp.
    two relays, two fuses, two circuits.

  9. #17
    I'm a grown up member now !
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    Thanks everyone. Got me thinking, I like the idea of twin fans, twin everything else. I bought the car with this setup and the previous owner had the same problems, he didn't even use a relay, I rewired and fitted a relay. Need to check in the morning, but I am sure both fans come on together, probably not designed this way, there is only one connection for both fans, I assume this is the way it is designed for the Seat, I take it their electronics would manage both fans as they were not designed to be wired the way this is.

    Again really appreciate the help everyone has posted.

    Any ideas what decent budged seats I could fit in it
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    Administrator blackpopracing's Avatar
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    If only one plug, then just cut the wires from the fans to separate into two feeds.

    I'd think about getting the first fan to run via a temp switch in the rad or top hose (a few options available there) with the second on a manual switch for traffic etc.
    If you are clever/have available space you could run two different temp switches-one for each fan, one low temp and one high temp.

    Otherwise just split the feed from the temp switch to two fused relays, making sure that the feed cables to all are rated correctly and that will sort it properly.

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