Thermal fuses

I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.

Did a bit of teching and found the thermal fuse in the blower motor resistor
pack is open.

New resistor pack is ~$90 I have located a ton of replacement substitutes
but I need to know the current and temp rating for the replacement.

Any help would be appreciated on the specifications or where I might source
the information.

An aside there seems to be a lot of fuse links in the van and no info on the
rating.

TIA

In article >, NotMe > wrote:
>I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.
>
>Did a bit of teching and found the thermal fuse in the blower motor resistor
>pack is open.
>
>New resistor pack is ~$90 I have located a ton of replacement substitutes
>but I need to know the current and temp rating for the replacement.

Bridge an ammeter across where the thermal fuse was. Find out what the
starting current is. Now, pick a Polyfuse that is rated for 1.5 times
that current. The polyfuse will give better motor protection and won't
fail, but it will cost more than a simple thermal fuse.. maybe as much
as two dollars.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" > wrote in message news:gg4fl5$s49
> Bridge an ammeter across where the thermal fuse was. Find out what the
> starting current is. Now, pick a Polyfuse that is rated for 1.5 times
> that current. The polyfuse will give better motor protection and won't
> fail, but it will cost more than a simple thermal fuse.. maybe as much
> as two dollars.
> --scott

I burned out two or three resistor packs for my Dodge full size van before I
"got it right".

Dont know if his Grand Caravan is similar, but would suspect it might be.

These resistor packs often burn out when the fan motor is having some
internal problems. You may not notice the problem other than for the
failure of the resistor packs. The current consumption can vary a lot, and
go up much higher than was designed for the circuit. In this case, the long
term cure is to change out the fan motor and replace the resistor pack.

In my case, I drilled into the resistor pack and installed an external 20
amp
fuse across the "burned" connection. This fuse has never blown, so I
believe
I am safe enough to install a new resistor pack (if I ever need to do so).
Since it works so well, there has been no incentive to replace it.

"Scott Dorsey" > wrote in message
...
: In article >, NotMe >
wrote:
: >I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.
: >
: >Did a bit of teching and found the thermal fuse in the blower motor
resistor
: >pack is open.
: >
: >New resistor pack is ~$90 I have located a ton of replacement
substitutes
: >but I need to know the current and temp rating for the replacement.
:
: Bridge an ammeter across where the thermal fuse was. Find out what the
: starting current is. Now, pick a Polyfuse that is rated for 1.5 times
: that current. The polyfuse will give better motor protection and won't
: fail, but it will cost more than a simple thermal fuse.. maybe as much
: as two dollars.
: --scott
:

thanks, we have several Grand C's in the extended family (foster to adopt)
from 04 to 06 max current is 13.5 amp give or take.

Is a Polyfuse a brand or a type (perhaps what I'm calling a thermal fuse) as
I suspect the fuse is not only for current over load but over temp as well.

In article >, NotMe > wrote:
>
>thanks, we have several Grand C's in the extended family (foster to adopt)
>from 04 to 06 max current is 13.5 amp give or take.

If you are sure the motor is good, pick that as a good baseline and get
a fuse that pops at 20 amps. If you're going for the polyfuse you could
probably use 15A.

Put a little light machine oil on the bearings og the blower and see if
that current drops a little bit. If it doesn't, don't worry.

>Is a Polyfuse a brand or a type (perhaps what I'm calling a thermal fuse) as
>I suspect the fuse is not only for current over load but over temp as well.

Polyfuse is a sort of resettable thermal disconnect that is based on a
material that is conductive when a solid but insulating when a liquid, so
the I/V curve has this abrupt discontinuity where it suddenly goes open
when the current or temperature exceeds a certain amount. It's a Raychem
trademark.

Other companies make clones of the thing, but Mouser carries the original
Raychem ones.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" > wrote in message
> If you are sure the motor is good, pick that as a good baseline and get
> a fuse that pops at 20 amps. If you're going for the polyfuse you could
> probably use 15A.


The current draw can vary wildly if the motor is bad. It can be hard to
know
for sure the motor is the problem because you may not see any overt
symptoms.
They can be seen with an o-scope, for example, but you may not see the
problem
with a simple current draw test with a VOM.

You may not hear any noise from the motor nor have any other indication.

I dont remember, right now, why I chose a 20 amp fuse. I think it was a
compromise between what the motor should draw and what I thought I needed
for protection to the resistor pack.

"HLS" > wrote in message news:%AjVk.8252

******First, I replaced the fan motor, then

> In my case, I drilled into the resistor pack and installed an external 20
> amp
> fuse across the "burned" connection. This fuse has never blown, so I
> believe
> I am safe enough to install a new resistor pack (if I ever need to do so).
> Since it works so well, there has been no incentive to replace it.

90 bucs don't seem right if it is the old wire type with the thermal breaker
they are about 25 bucs

Scott Dorsey wrote:

> In article >, NotMe > wrote:
> >I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.
> >
> >Did a bit of teching and found the thermal fuse in the blower motor resistor
> >pack is open.
> >
> >New resistor pack is ~$90 I have located a ton of replacement substitutes
> >but I need to know the current and temp rating for the replacement.
>
> Bridge an ammeter across where the thermal fuse was. Find out what the
> starting current is. Now, pick a Polyfuse that is rated for 1.5 times
> that current. The polyfuse will give better motor protection and won't
> fail, but it will cost more than a simple thermal fuse.. maybe as much
> as two dollars.
> --scott
>
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

"man of machines" > wrote in message
...
: 90 bucs don't seem right if it is the old wire type with the thermal
breaker
: they are about 25 bucs

Best I could find was $87.50 and when I went to pick it up the part was on
"back order".

I've patched the old one and am seeking a replacement for the thermal fuse.


:
: Scott Dorsey wrote:
:
: > In article >, NotMe >
wrote:
: > >I have an 04 dodge Grand Caravan and the front HVAC blower motor quite.
: > >
: > >Did a bit of teching and found the thermal fuse in the blower motor
resistor
: > >pack is open.
: > >
: > >New resistor pack is ~$90 I have located a ton of replacement
substitutes
: > >but I need to know the current and temp rating for the replacement.
: >
: > Bridge an ammeter across where the thermal fuse was. Find out what the
: > starting current is. Now, pick a Polyfuse that is rated for 1.5 times
: > that current. The polyfuse will give better motor protection and
won't
: > fail, but it will cost more than a simple thermal fuse.. maybe as much
: > as two dollars.
: > --scott
: >
: > --
: > "C'est un Nagra. C'est suisse, et tres, tres precis."
:

In article >, NotMe > wrote:
>
>"man of machines" > wrote in message
...
>: 90 bucs don't seem right if it is the old wire type with the thermal
>breaker
>: they are about 25 bucs
>
>Best I could find was $87.50 and when I went to pick it up the part was on
>"back order".
>
>I've patched the old one and am seeking a replacement for the thermal fuse.

Try Raychem part RUE300. Mouser should stock it.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."