Car heater fan resistor pack thermal fuse query

The thermal fuse in the resistor pack in my 1997 Fiat Ducato has blown. I've tried cleaning it up but I can't see any markings at all. With the fuse bypassed, all the fan speeds function correctly.

Any idea how I can find out what to replace it with?

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Tim

Reply to
Tim+
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Quick trip to maplins will sort that out

Reply to
steve robinson

No Maplins handy and besides, what value fuse? They seem to come in a lot of different temperature ratings.

Maybe I should just take a punt on something like this?

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Tim

Reply to
Tim+

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RS components ,think mine cost me 12 pence , easy to change , stick it in the freezer with a couple of crocadile clips use them has heat sinks when you solder it in , use lead based solder lower melting point

Reply to
steve robinson

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And how did you know what rating to buy...?

Tim

Reply to
Tim+

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I am not sure it's THAT critical If its designed to cut out if things get too hot, then anything round the 80-100C mark should be OK

Reply to
The Natural Philosopher

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the one above appears to be 152 degrees C

Reply to
Mrcheerful

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On the focus it was stamped on the fuse

Reply to
steve robinson
[...]

IMO, that's way too low; the thermal fuse for the Ford Focus is rated at

215C for example.

The OP needs to find why the fuse failed in the first place. There needs to be good airflow through the system; no blocked cabin filter (if fitted), and no leaves or other items blocking it.

Another common reason for the fuse failing is the fan bearings on the way out; on the lowest speed, the extra drag of tight bearings will not allow enough airflow to cool the resistor pack.

Chris

Reply to
Chris Whelan

Some sources here

Reply to
alan

Thanks, some useful tips there.

Tim

Reply to
Tim+

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Lucky you! If you re-read my original message you'll see that there are no markings on mine.

Tim

Reply to
Tim+

You surprise me but I bow to superior knowledge. I have used stuff like that on electronics..215C will in general have melted the solder on the component before it blows....which leads to the interesting though that that is who to make one of these. Blob of solder on two wires..job done..

Above my pay grade,. but sounds eminently plausible

Reply to
The Natural Philosopher

In the two cases where I've have replaced similar fuses the replacements rated at 150/160C have lasted for many years afterwards.

On one repair I checked the motor and it was running rough. Water had got onto the motor shaft and it was rusting. Two drops of engine oil (obtained from the end of the dip stick) on the bearings restored smooth running.

On a 2001 ford focus part of the cabin filter cover is the seal at the base of the windscreen and this can leak if incorrectly fitted or the plastic clips break when replacing the cover. Water then can run thought the filter, through the blower motor and into the passenger side foot well.

Reply to
alan

I am not sure it's THAT critical If its designed to cut out if things get too hot, then anything round the 80-100C mark should be OK

I would agree.

Surely the whole purpose of a thermal fuse is to fuse when temperatures get to such a point that it might start melting things, or start a fire.

The Nissan fuse highlighted in this thread would appear to fuse at 150 degrees C - I'm not sure I would fancy something that hot in my car should the fan motor stall or the airflow gets blocked.

I'd go with the 80 - 100C suggested here, and if it blows you then have a proper problem to sort out.

Gareth

Reply to
Gareth Magennis

80C may be towards the higher end of the temperature that a car interior may reach when parked in full sun on a summers day.
Reply to
alan

You don't solder thermal fuses, because it blows them. ;-)

They are crimped or spot welded. When replacing, you can cut the wires and use a couple of the brass inserts out of a chocolate block connector strip (usually have to pull them out of the plastic strip, as these are often used where the plastic might melt and make a mess).

Old series heater TV sets used drop-off resistors in a similar way. Resistors soldered to the underside of a couple of terminals, and if there's excess current, the solder melts and they drop off. IIRC, they were typically used in the 300mA heater chain so that if one valve developed a heater to cathode short, the resistor might drop off before several other valves were wrecked, and also on the main supply dropper resistor so that if someone blocked the ventilation holes, the set was (slightly) more likely to cut off before the curtains were set alight.

Reply to
Andrew Gabriel

Arr. They don't make em like they used to in my day.:-)

Have you ever read the book by John Cunninghams navigator - its about the night fighter and the development of Radar..and how the early sets all failed with *That Smell*.

Nightfighter by Jimmy Rawnsley.

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oddly amazon starts at £38 whereas waterstones has it for £5.99

anyway, all valves and klystrons and then magnetron in them days. Voltages to make yer hair stand on end and you loved the smell of baking phenolic resin in the morning.

Reply to
The Natural Philosopher

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I take it you've read Alfred Price's book Instruments of Darkness:

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I read it as a young schoolboy, and was captivated by it.

Reply to
Terry Fields

In message , Terry Fields writes

Damaged Selenium rectifiers used to emit a particular pong which others may remember.

I also read and enjoyed the book.

Cunningham was flight testing Vampires over my head as I grew up.

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Reply to
Tim Lamb

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