Hi,
The glass type 5A fuse in the switch to my tiller pilot blew the
other day. The manual calls for a 12A fuse. Replaced fuse with one from
local hardware shop but switch wont function at all with this one. It
was a 15A 3AG or 3WG (will replace with 12A asap). Is this because it's
a 240V fuse? Are there fuses specifically for 12V DC? Have tried other
switches with fuse with same result.

Thanks for your advice in advance

MEC inscribed in red ink for all to know:
Hi,
The glass type 5A fuse in the switch to my tiller pilot blew the
other day. The manual calls for a 12A fuse. Replaced fuse with one from
local hardware shop but switch wont function at all with this one. It
was a 15A 3AG or 3WG (will replace with 12A asap). Is this because it's
a 240V fuse? Are there fuses specifically for 12V DC? Have tried other
switches with fuse with same result.

Thanks for your advice in advance


Fuses are pretty much voltage insensitive (OK, some nitpickers will
probably jump on me here). If the instrument still doesn't work, consider:

o the new fuse is bad (it happens)
o the fuse doesn't fit the fuse holder (contact is not being
made with both metal ends of the fuse)
o the fuse holder is damaged
o the tillerpilot is bad

I hope it isn't the last item, but something caused the fuse to blow...

bob
s/v Eolian
Seattle

"MEC" wrote in news:1166737416.477032.162250@
42g2000cwt.googlegroups.com:

Hi,
The glass type 5A fuse in the switch to my tiller pilot blew the
other day. The manual calls for a 12A fuse. Replaced fuse with one from
local hardware shop but switch wont function at all with this one. It
was a 15A 3AG or 3WG (will replace with 12A asap). Is this because it's
a 240V fuse? Are there fuses specifically for 12V DC? Have tried other
switches with fuse with same result.

Thanks for your advice in advance



No, The 240V rating on the fuse is the highest circuit voltage the fuse
is rated to interrupt. At higher voltages, its melted-open gap may arc
when it melts. You may use a 240V fuse on any circuit LESS than 240V.
12V is fine....

Did the 15A fuse blow, too?

Fusing on a circuit is normally quite a bit more than the circuit
actually draws but no more than the wiring the fuse protects is rated
for. Europeans fuse their equipment lots closer than Americans, which is
sometimes frustrating with nuisance blows on good equipment, just because
there was a momentary current charging power supply capacitors or the
like, for instance. If it draws 10A, fuse it for 15A, 50% over normal
load. Fuses do NOT protect fragile electronics from surges. Fuses are
thermal beasts and FAR slower to blow than diodes, transistors, ICs, and
other electronic components. To protect electronics from voltage surges
on DC circuits, we use a special sensing IC that fires a device to ground
the offending overvoltage condition, blowing the fuse, when the fuse gets
around to it. Under no circumstances will those protectors allow
overvoltage to appear on the protected electronics.

Of course, those protective circuits cost money and reduce profits, so
most consumer electronics, such as you buy for your boat, don't have
them. We need to sell you new stuff at regular intervals, planned
obsolescence, you know. The other trick is to put something like charts
on proprietary memory ROMS noone else is allowed to produce. After the
next series of chartplotters comes out, you simply stop producing charts
for the one you want to die, like my Garmin GPSMAP 185S. You put
"Discontinued" on its webpage, trying to render it useless and valueless
so they all have to go buy the next generation of nonsense they don't
need. It's an old NMEA trick that's worked for years.....

The other trick is to come out with a "new, improved" version of
incompatible NMEA data at a different rate.....NMEA 2000.

Thanks,
The 15A fuse didn't blow, the led on the control panel switch just
doesn't light up. This is a switch with its own a fuse. Switch is rated
to 20 A.
If I put another 5A fuse in from a different switch the switch led
light comes on and the instruments connected to it come on. As
suggested it seems the problem may be with the new fuse. I believe I
tried several new fuses, late at night mind you. The new fuses are
about 3mm longer than the 5A but they are held in with a spring device
so I wouldn't think this would matter.

I've just gone and bought some new 5A and 7.5A fuses made by same mob
as the 15A. I'll post back my findings.

Larry wrote:
"MEC" wrote in news:1166737416.477032.162250@
42g2000cwt.googlegroups.com:

Hi,
The glass type 5A fuse in the switch to my tiller pilot blew the
other day. The manual calls for a 12A fuse. Replaced fuse with one from
local hardware shop but switch wont function at all with this one. It
was a 15A 3AG or 3WG (will replace with 12A asap). Is this because it's
a 240V fuse? Are there fuses specifically for 12V DC? Have tried other
switches with fuse with same result.

Thanks for your advice in advance



No, The 240V rating on the fuse is the highest circuit voltage the fuse
is rated to interrupt. At higher voltages, its melted-open gap may arc
when it melts. You may use a 240V fuse on any circuit LESS than 240V.
12V is fine....

Did the 15A fuse blow, too?

Fusing on a circuit is normally quite a bit more than the circuit
actually draws but no more than the wiring the fuse protects is rated
for. Europeans fuse their equipment lots closer than Americans, which is
sometimes frustrating with nuisance blows on good equipment, just because
there was a momentary current charging power supply capacitors or the
like, for instance. If it draws 10A, fuse it for 15A, 50% over normal
load. Fuses do NOT protect fragile electronics from surges. Fuses are
thermal beasts and FAR slower to blow than diodes, transistors, ICs, and
other electronic components. To protect electronics from voltage surges
on DC circuits, we use a special sensing IC that fires a device to ground
the offending overvoltage condition, blowing the fuse, when the fuse gets
around to it. Under no circumstances will those protectors allow
overvoltage to appear on the protected electronics.

Of course, those protective circuits cost money and reduce profits, so
most consumer electronics, such as you buy for your boat, don't have
them. We need to sell you new stuff at regular intervals, planned
obsolescence, you know. The other trick is to put something like charts
on proprietary memory ROMS noone else is allowed to produce. After the
next series of chartplotters comes out, you simply stop producing charts
for the one you want to die, like my Garmin GPSMAP 185S. You put
"Discontinued" on its webpage, trying to render it useless and valueless
so they all have to go buy the next generation of nonsense they don't
need. It's an old NMEA trick that's worked for years.....

The other trick is to come out with a "new, improved" version of
incompatible NMEA data at a different rate.....NMEA 2000.

The fact that you refer to a 240v fuse leads me to suspect that you are in
the UK or an area based on the UK mains system.

If so the 240v fuses from your hardware shop will not work on your 12v boat
systems as the are slightly different sizes and will not make a good contact

Try a car shop for 12v fuses and get one exactly the same physical size.

Alec


"MEC" wrote in message
ups.com...
Hi,
The glass type 5A fuse in the switch to my tiller pilot blew the
other day. The manual calls for a 12A fuse. Replaced fuse with one from
local hardware shop but switch wont function at all with this one. It
was a 15A 3AG or 3WG (will replace with 12A asap). Is this because it's
a 240V fuse? Are there fuses specifically for 12V DC? Have tried other
switches with fuse with same result.

Thanks for your advice in advance