Loud Thump When e-fan turns off

[gizmo_21]

Hey Guys

I might have a tricky one for you!!

I just installed a e-fan into my truck and since i've done this i get a loud thump from my subs everytime the fan turns off, this happens at any volume and the thump (no matter how high/low the volume is) will stay at the same audioable level..

Is there something to prevent the "excess Voltage" from spiking my system??? (not sure if this is the right idea, but i think the fan is dumping it's voltage (when clicking off) into the cars elecrtical system and my sound system is picking it up) any way to stop this??

THanks in advance

Ry

[flyingbrick]

Are you running a capacitor? if not, that's the only ''filter'' that i know of but that's for AC, might work for DC. Unless someone knows something i don't.

[gizmo_21]

Are you running a capacitor? if not, that's the only ''filter'' that i know of but that's for AC, might work for DC. Unless someone knows something i don't.

Nope no capacitor, i'm just running dual batteries, with an explorer alternator...

I was thinking of possibley a diode, but not sure which line to put it in, +ive fan (i think it's this one) or the + amp...

Thanks flyingbrick!!!! though, i'm pretty sure a diode is similar to a capacitor, but not sure!!

[flyingbrick]

Nope no capacitor, i'm just running dual batteries, with an explorer alternator...

I was thinking of possibley a diode, but not sure which line to put it in, +ive fan (i think it's this one) or the + amp...

Thanks flyingbrick!!!! though, i'm pretty sure a diode is similar to a capacitor, but not sure!!

I'd try the diode and yes in the positive line, alltho i have not ever seen a (properly) running electric fan back feed or draw a lot of power when turning off.

[gizmo_21]

I'd try the diode and yes in the positive line, alltho i have not ever seen a (properly) running electric fan back feed or draw a lot of power when turning off.

lol... you haven't tried the turaus 3.8L Fan!!! lol

http://www.fordmuscle.com/archives/2003/02/electricfan/index.php

these bad boys pull 40 Amps... sweet i'll try the diode... thanks for the help!!!!!

Ry

[Bob Ayers]

If the relay is working properly, the voltage spike from the Di/Dt should not be feeding back into the electrical system.

Make sure the relay coil has a diode across it.

[06RangerXLT]

http://www.fordmuscle.com/archives/2003/02/electricfan/schematic.gif
The diagram shows how to use the fan controller to fire the Bosch relay. A reverse current blocking diode (or freewheeling diode) is a good idea on any motor control relay. Once power is removed from a DC motor it becomes a DC generator and the reverse voltage spike can shorten the life of the relay. The diode will bleed this spike to ground. The 1N5408 diode can be found at any electronics store for just a few dollars.