Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Cheers, T i m

T i m wrote:
Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Cheers, T i m


Thermal fuse?

T i m wrote:
Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Cheers, T i m

Maybe it stops current coming back from the motor when in a speed setting
that does not use that particular route to get to the motor.

T i m wrote:
Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Cheers, T i m

if there is more than one could you test the other to see what it does?
Thermal fuse is possible. are there any markings at all on it? Diodes
usually are black with a line or two at one end. Thermal fuses usually have
a temperature on them.

On Wed, 17 Feb 2010 12:07:02 GMT, "Mrcheerful"
wrote:

T i m wrote:
Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Cheers, T i m

if there is more than one could you test the other to see what it does?
Thermal fuse is possible. are there any markings at all on it? Diodes
usually are black with a line or two at one end. Thermal fuses usually have
a temperature on them.


Thanks both,

I only looked at it briefly and initially it looked like a diode as
one end was pointy and marked red (it was maybe 15mm long x 5mm
diameter, generally silver and I think there were some markings but
not easy to read as it was still within the frame thing. It was an
axial device and free standing on it's own leads that were crimped
into the system).

If he's still got it when I pop in later I'll have a closer look.

I didn't get chance to see the replacement unit or stick a meter on it
(which might have been handy).

Cheers, T i m

T i m wrote:
On Wed, 17 Feb 2010 12:07:02 GMT, "Mrcheerful"


Thanks both,

I only looked at it briefly and initially it looked like a diode as
one end was pointy and marked red (it was maybe 15mm long x 5mm
diameter, generally silver and I think there were some markings but
not easy to read as it was still within the frame thing. It was an
axial device and free standing on it's own leads that were crimped
into the system).

If he's still got it when I pop in later I'll have a closer look.

I didn't get chance to see the replacement unit or stick a meter on it
(which might have been handy).

Cheers, T i m


One like this?.

http://www.indiabizclub.com/uploads0...4182770844.jpg

Paul wrote:
T i m wrote:
On Wed, 17 Feb 2010 12:07:02 GMT, "Mrcheerful"


Thanks both,

I only looked at it briefly and initially it looked like a diode as
one end was pointy and marked red (it was maybe 15mm long x 5mm
diameter, generally silver and I think there were some markings but
not easy to read as it was still within the frame thing. It was an
axial device and free standing on it's own leads that were crimped
into the system).

If he's still got it when I pop in later I'll have a closer look.

I didn't get chance to see the replacement unit or stick a meter on it
(which might have been handy).

Cheers, T i m


One like this?.

http://www.indiabizclub.com/uploads0...4182770844.jpg

http://images.google.co.uk/imgres?im...%3D36%26um%3D1

40p!

In article , T i m says...

Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Assuming it is a diode..
It is there to prevent back EMF flowing into the wiring and knackering
any electronics that may get damaged.

BUT, it could also be a thermal fuse. If its a Ford, it is a thermal
fuse which fails usually due to the pollen filter being blocked.

--
Conor

I'm not prejudiced. I hate everybody equally.

On Wed, 17 Feb 2010 12:28:37 +0000, Paul
wrote:

Paul wrote:
T i m wrote:
On Wed, 17 Feb 2010 12:07:02 GMT, "Mrcheerful"


Thanks both,

I only looked at it briefly and initially it looked like a diode as
one end was pointy and marked red (it was maybe 15mm long x 5mm
diameter, generally silver and I think there were some markings but
not easy to read as it was still within the frame thing. It was an
axial device and free standing on it's own leads that were crimped
into the system).

If he's still got it when I pop in later I'll have a closer look.

I didn't get chance to see the replacement unit or stick a meter on it
(which might have been handy).

Cheers, T i m


One like this?.

http://www.indiabizclub.com/uploads0...4182770844.jpg

Hmmm ..

http://images.google.co.uk/imgres?im...%3D36%26um%3D1

40p!

Yup, that's more like it, except the one I saw had a red not black
end. I wonder if that indicates anything (like temp rating) or just
peculiar to a particular manufactures design. I'll see if he's still
got the old one and if any of the markings match up. [1]

Anyroadup, well it looks like we may have solved the puzzle, thanks.

Now, anyone know if you can bump start a Ka heater valve with a
screwdriver handle like you could with the old Ford auto choke carbs?
(Till it's a bit warmer out there to fit a new one). :-)

Cheers, T i m

[1] Speaking to another guy he said he just shorted his 'thing'
(thermal fuse) out and it worked fine from then on (as it should under
normal circumstances). Must be a reason for them to be there though
(even though the feed is fused etc) ... prevent a seized fan allowing
stuff to catch fire as the resistor coils glow red hot in there maybe?

On Wed, 17 Feb 2010 13:44:14 -0000, Conor wrote:

In article , T i m says...

Hi all,

I was looking at a resistive heater fan speed controller on the bench
the other day and it would appear that it had 'failed' because of what
looks like a diode that sits near the coil/resistors (I believe the
whole thing sits in one of the internal air hoses).

It seemed a shame to have to replace the whole thing (it looked new)
for what could be a 2d component?

Anyone played with such and is it a straight rectification diode
(rather than zener etc) and any idea what function it performs please?

Assuming it is a diode..
It is there to prevent back EMF flowing into the wiring and knackering
any electronics that may get damaged.

That's what I suggested to the guy who said he's shorted his failed
one out.

BUT, it could also be a thermal fuse. If its a Ford, it is a thermal
fuse which fails usually due to the pollen filter being blocked.

Ah, makes good sense. With the blower on low most the resistors would
be dissipating the surplus energy and with poor airflow it all
overheats.

Funny, I showed the Mrs a heat-pipe cooler off a failed laptop that
had died through overheating for similar reasons (the whole fin area
was blocked with fluff / dog hairs etc). Handy having an airline at
home. ;-)

Cheers, T i m