[FC] Problem after installing High Volume Blower Motor

[Andy]

I have to respectfully disagree Joel.  The fan spinning down absent of power is what turns the fan motor into a generator for a second or two.  That is the backfeeding that is harmlessly routed to ground through a correctly placed diode.  The diode is just tapped into the hot wire and the other end is grounded.  The diode is not in series on the hot wire ever.  The backfeed current is minimal - hence the small diode.  I recommended a particular 3amp diode because they are easy to work with without a magnifying glass and tweezers - but are still way overkill amp wise.

Saying it doesn't matter which way a diode is hooked up is like saying it doesn't matter what end of the gun you are on.  I prefer to be on the stock end... not the barrel.  

There are so many variables that even guys with the exact same fan wiring may not experience the same run on.  How "tight" is the fan motor, the weight of the fan (flywheel effect)... type of ignition system... resistor or not inline feeding the ignition.  I bet Andrew's van doesn't run 2 seconds after he turns the switch.  Some peoples may run a half second or full second and never even notice it.


YMMV

-----Original message-----
From: Joel McGregor <joelsplace at earthling.net>
To: "Andy ." <rumbleseat66 at hotmail.com>, "corvanatics at corvair.org" <corvanatics at corvair.org>
Sent: Tue, Nov 1, 2011 18:33:48 GMT+00:00
Subject: RE: [FC] Problem after installing High Volume Blower Motor

If hooking it up backwards fries the diode then the diode won't be sufficient to keep the system from back feeding as that will also fry it.
Draw a picture of how it's wired, post it somewhere we can get to it and we should be able to figure out what's going on.
I've got relays protecting all the fan speeds on my '65 and no feedback problems.  My relays are the cheapest ones I could find.
Joel McGregor


> Well, whether it had the diode or not is irrelevant now because when the 85 and 86 terminals are hooked up backwards the diode blows immediately.