Power requirements for Nuvi 660, 760 Solution

After a lot of testing, I found my meter was giving bad results - too
high on voltage. Problem was the 9V battery in the meter was low, so
I replaced it and got good readings to work from.

What I found was a "leaking" fuse. During the process of tracing the
path of power from the battery, I was getting ready to do some fuse
panel checks, and for some onkbown reason, decided to change the 20A
cig lighter/aux power fuse. While out of the circuit, I held it up
to the light and could clearly see the filament between the two
blades was broken. I checked it with a meter set for continuity and
when I applied the test leads, a small LED on the top of the fuse lit
up. The fuse (labelled Smart Glow) is supposed to light up if it
blows so that you can see which one blew. BUt how does it get its
power if the circuit is broken ? I don't know, but apparently it
will allow a reduced amount of voltage to come through the circuit,
which is why I was getting (after meter battery replaced) 10.1 VDC
reading at the lighter/aux sockets.

Now I don't know about you, but I have always understood a fuse,
when working properly, to completely shut down the circuit it was
supposed to be protecting, not allow some power to get through. Maybe
they think the circuit is protected with reduced voltage?

I talked with a technician who verified that these types of fuses
sometines leak like this one - but said in his experience, they did
so all the time, inspite of the manuf's cautions. He said that this
type of fuse causes more problems than it fixes, and besides, if you
know what in the car is failing (wipers, radio,etc.) you just look at
the fuse map found on the fuse box lid and pull and test the
appropriate fuse. He advised me to throw all my spares of that type
in the trash, and go get some "real" fuses, and in addition check to
see if there were any like that in te panel and replace them. I'm
headed out this PM to do this.

Mystery solved, one of those things we used to call a "funny", which
we experienced all the time back in the days of computer mainframes
with discrete component circuit cards.

On 21 Jul 2011 17:51:43 GMT, John Carter wrote:


Does this relate to an earlier post of yours? It would've been helpful
if you had replied in thread.

It makes sense. Clearly an LED circuit must have a finite resistance, so
as to allow the current to flow that lights the LED. Thus a
high-resistance device would end up powered through the fuse, as long as
there was no low-resistance load also in series with the fuse. For a
hypothetical example, a 100 kilohm LED in series with a 1 megohm load
would reduce the voltage by ~10% instead of cutting it off.

--
Gene E. Bloch (Stumbling Bloch)

I'm sorry. It does, but I'm not on my own computer today, so didn't
have post at hand. The original post, I thought was the same subject,
maybe worded differently.

On 21 Jul 2011 20:05:55 GMT, John Carter wrote:


Thanks for the reply.

Since you have now been properly chastised, I can crawl back into my
hole (that's meant to be humor!).

Of course it was good of you to update us (I did somewhat remember the
other thread), and I did mean it as a suggestion, not a criticism.

--
Gene E. Bloch (Stumbling Bloch)

Didn't think of it as criticism - I can always use a suggestion and I
appreciate it.