[DeTomaso] Electrical nightmare scenario...

[Doug Braun]

Mike,

	What's the thinking behind the radiator fan coming on whenever you activate
the interior heater/blower fan?  If you're turning on the heater, that
removes heat from the system so the radiator fan is needed less.  If you're
turning on your air conditioning then that would be a reason to turn on the
radiator fan but why not just let the thermal switch do its job only as
needed?  Is this the stock setup?

Doug Braun
blue 73L #5505

PS:  I never trust the "look" of a fuse.  I always test a suspect fuse with
a voltmeter set to its lowest Ohms scale.  Anything reading above what you
get when you touch the meter's leads together is a suspect fuse.  I prefer
the glass fuses because of the way the plastic ones make it so easy to
damage the fuse's conductor with your fingers.

-----Original Message-----
From: detomaso-bounces at realbig.com
[mailto:detomaso-bounces at realbig.com]On Behalf Of MikeLDrew at aol.com
Sent: Friday, December 21, 2007 3:02 PM
To: DeTomaso at realbig.com
Subject: [DeTomaso] Electrical nightmare scenario...


Hi guys,

I spent the day before yesterday locked in mortal combat with my daily
driver
VW Scirocco.   There is Pantera relevance to this story, so bear with me.

After years of driving it everywhere, I decided to treat it to a tune-up
(although arguably it probably didn't really 'need' it).   New plugs, wires,
cap
and rotor, and it ran just as well as before.   For no particular reason I
decided to ops-test the electric radiator fan, so I let it sit and warm up
in my
driveway while I put the various tools away (itself an almost unheard-of
condition).

I was in the back of my garage merrily organizing my wrenches and sockets
when I heard SPLOOOSH!!!, turned around and saw a geyser erupting from my
radiator!

Sure enough, the radiator fan never turned on.   With visions of blown head
gaskets in my head, I did a dance worthy of Baryshnikov through the piles of
parts and debris on my garage floor to race to the Scirocco and shut it off.

Okay, so now why didn't the fan work?   It is actuated by two independant
means--either by the thermoswitch in the radiator, or automatically anytime
the
interior heater/blower fan is turned on.

Neither method would get any action from the fan.   The first thing to do,
of
course, was to check the fuse.   I opened the fusebox and all the fuses were
visibly good.

I then proceded to do some basic troubleshooting.   Disconnecting the
connector from the back of the fan, I rigged up some jumper wires and ran
them
straight to the battery--VAROOM!   Okay, so the fan motor itself works.   I
then got
out my voltmeter and tested the connector; with the fan switch on the dash
turned on, there was 12.7 volts.

Okay, so let me get this straight?   I've got power at the plug, and the fan
motor runs when you give it power, but when you plug the plug into the fan,
it
doesn't work?

Electricity is my weak area and I quickly call for backup when I get in
situations like this.   I keep SOBill Taylor's phone number on speed dial
for just
this sort of occasion.   I called him up and explained the scenario, then
scanned the factory wiring diagrams and e-mailed them to him.   Together we
conjured up several likely scenarios; I would hang up, spend a few minutes
testing/troubleshooting, eliminate that potential cause, and then call him
back for
another lead.

Eventually every wire and connector had been tried and tested, and
everything
was checking out good.   The last possible problem area was confined to the
fusebox itself.

A couple of hours (at least) had passed by this point, and then I physically
removed the (Pantera-style) fuse from the fusebox, and this is what I found:

http://members.aol.com/mikeldrew/BadFuse.jpg

My 'good' fuse was anything but!   Sure, it was good where a fuse is
supposed
to go bad when it DOES go bad, but hidden from view under the prongs of the
fusebox, the fuse was totally wasted!

Simply popping another fuse into the holder instantly fixed the problem!

During the course of my troubleshooting I cleaned all the various connectors
in the system, so hopefully any excess resistance has been resolved.   But
the
lesson learned here is that 'checking the fuse' doesn't mean merely looking
at it sitting in the fusebox.   It means removing it, inspecting it and then
reinstalling it!

BTW, some people have suggested replacing these old-fashioned fuses with
glass fuses.   But I have had poor luck with glass fuses, because when a
circuit
goes bad (but not terminally bad), they would heat up and melt internally,
completely out of view.   Instead of blowing, they would simply stop
working, but
even when looking at it in your hands, there would be no visible indication
of
failure.   At least with these ceramic fuses, when they go bad, it's visible
evident.

That is, assuming you take the time to actually LOOK at the thing!

Sheesh.....

Mike


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