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MG TD TF 1500 - Wiring Question, Electric Fan TF1500

I am installing an electric fan in front of the radiator on a TF, for supplemental cooling. The two wires leading from the fan appear to be 16gauge and are about 18 inches long. The instructions call for an inline 25 amp fuse and a switch, both not included in the kit. The fuse box I found at the local Autozone store can accomodate up to a 30 amp fuse and the lead wires in and out of the fuse box are 12 guage. I will use a 25 amp fuse in the inline fuse box and my question is what guage wire should I use to complete the circuit. Thanks. Jim Bradley
J.S. Bradley

I would opt for the larger diameter wire of the two.
David Werblow

If you are going to use a 25 amp fuse you should use 10 AWG wire. 12 gauge wire is nominally good for 20 amps and 10 gauge is good for 30 amps. The fuse should protect the wire. The switch should be adequately rated also, although most of these radiator fans do not draw more than 20 amps.
Dallas Congleton

Jim, find out what current the fan draws and use a fuse slightly above that value. The only thing that the fuse is protecting is the 16 ga. wire attached to the fan. I see no reason to use wire heavier than 16 ga. unless you have a very long wiring run The only justification for a 25 amp fuse might be due to a large surge current when the fan turns on. IMHO. Bud
Bud Krueger (TD10855)

X2 with Bud....An electric fan does not pull more than 7-8 amps, (when it first kicks on), under normal conditions, and a #16 wire is adequate....especially since the fan itself has #16 leads....Use #14 , if that makes you feel better, but it has no real additional protection value.
Edward
E.B. Wesson

Jim, your question was what wire to use with a 25 amp fuse, which is what was provided with the fan by the manufacturer. The "correct" answer is the same - the wire size should be adequate to carry the amount of current that the fuse does, or the wire will burn before the fuse blows under load or a fault which could occur in the event of a short even if the actual fan running load is normally below that rating.

Bud's observation that the initial surge will blow a lighter fuse is correct and that the normal fan load is much lighter so in actual application a short run of wire sized for the actual fan load could be adequate as it could temporarily withstand the initial surge of the fan start, but small gauge wire will induce some voltage drop at this point, so..., why not provide an adequately sized feed ?

Also the fuse is normally a slow blow type to overcome the starting surge of the fan. This current surge and the delay will also be felt by the wiring so I would not go too small.


Dallas Congleton

To All,
Thanks for your input. I returned the 16ga wire and got 14ga instead.
I have done a test with a ground near the fan, although not installed, and the inline fuse and toggle switch on the hot side tied into the fuse connection for the horn. It works and should allow me to run the fan when the ignition is off, which I would like to be able to do. Hopefully I will not forget and leave the car and have it run down the battery.
Again thanks for your help. Further coments on the propsed circuit would also be appreciated. Jim Bradley
J.S. Bradley

Jim,

I strongly suggest you reconsider the location of your electric fan. As a "pusher", ie: on the front of the radiator, you'll find that the whole fan apparatus will impede airflow and reduce the cooling efficiency of your rad.

Before going to Gatlinburg in 2006, I tried one as a pusher and immediately noticed the rise in coolant temp, and that was in normal daytime temperatures ~ 25ºC (around 75f). I anticipated much higher temps in Tennessee.

Installing as a "puller" meant of course, removing the whole radiator assembly, which I reluctantly did. I removed the old “hand-chopper” 4-blade fan completely, also the spacer, and mounted a 12" Hayden on the backside of the radiator. A pic is attached.

This turned out to be a wise move and it has run beautifully since, including some wicked days in Gatlinburg. I also replaced the anti-freeze with Water-Wetter.

The temperature sensor, which I carefully brazed into top of the rad, works well, but I suspect the sensor that comes with the fan, is almost as good. Mount it as low as possible and not high, like mine. It is wired to a Man-Off-Auto switch.

Gord Clark
Rockburn, Qué.

Gordon A Clark

Gord,
Thanks for your suggestion and the pictures, but it is too late...I already have the fan installed and am starting to reinstall the grill. There is no turning back. I will let you know how it works in a Virginia summer, and I will let Moss Motors know as well!!!
I initially rejected the "puller" set-up because the modification is readily apparent to the purist. An interim set-up for me might be to retrofit a newer six-blade fan in lieu of the original four blade...but one step at a time. Thanks Jim Bradley
J.S. Bradley

This thread was discussed between 23/06/2011 and 24/06/2011

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