choice of "thermo-fan" switch temperature

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bryan - 18 Aug 2007 21:13 GMT

i presume that the most significant consequences from selection of a
low radiator fan switch temperature setting (e.g. 75-deg-C) gives you
more aggressive cooling with the expense of running the fans more and
possibly the battery and that's it. so the fans might need
replacement early, and if one is lucky, the engine will be subject to
smaller temperature fluctuations. if we consider this relative to a
setting of 85/93-degrees-C (pelican item 951-606-481-00-85-M2 for '87
944NA), _how_ significant is this difference? over how long a time
frame?

-bryan

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William Noble - 19 Aug 2007 01:06 GMT

I would not go for the lower temperature - you want your engine running
warm, but not overheated. And, fan motors are about $300 each if I remember
right, keep that in mind - in my experience, the usual failure is the front
bearing seizing up - it's possible to replace, but not easy (undo a bunch of
spotwelds, etc)

>i presume that the most significant consequences from selection of a
> low radiator fan switch temperature setting (e.g. 75-deg-C) gives you
[quoted text clipped - 7 lines]
>
> -bryan

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dave AKA vwdoc1 - 19 Aug 2007 03:07 GMT

I agree with nobody@nowhere.com and that these engines run better and more
efficiently warm (normal operating temp).

I have been told to match the thermostat with the proper temp fan switch.
AFAIK You want the thermostat and fans to work together not against each
other. Normally the thermostat opens up and then when the radiator gets hot
enough the fans come on.
If the fan comes on too early, due to a lower temp fan switch, then the
coolant going back into the engine will be too cool and the thermostat
closes due to the engine becoming too cold. I see jumps of coolant
temperature readings.
You want a relatively stable temp. ;-)

So if you were going to boil water or add water to the boiling water, would
you grab the water from the refrigerator or some stored at room temperature?
You would burn a little more energy with the colder H20 from the fridge.
Easier on the system if the temps are close to one another! ;-)

At least that is how I see it! ;-)
Does this make sense?

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later,
dave
(One out of many daves)

>I would not go for the lower temperature - you want your engine running
>warm, but not overheated. And, fan motors are about $300 each if I
[quoted text clipped - 12 lines]
>>
>> -bryan

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Nate Nagel - 20 Aug 2007 00:09 GMT

Perfect sense. In short, the fan cut-in temp. should be somewhat higher
than the coolant thermostat.

nate

> I agree with nobody@nowhere.com and that these engines run better and more
> efficiently warm (normal operating temp).
[quoted text clipped - 16 lines]
> At least that is how I see it! ;-)
> Does this make sense?

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replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

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jolie - 25 Aug 2007 19:34 GMT

What are you all talking about? Re-designing the Porsche already designed
temperature sensors' settings?
Porsche did what you all are discussing...ALREADY!!! Think they know more
than y'all ???

Just use what the manual specifies. The original part number.

Remember my last Porsche 944 1983, lasted 550,000 miles before it was hit in
the rear. Original engine, original transmission. That engine doesn't care
too much about temperature extremes...for over 550,000 miles I did a lot of
testing, wouldn't you all agree? NYC driving too.

I never played around with different thermostat or temp ranges on the
sensors. As a matter of fact, I never even changed the thermostat...on
either Porsche

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joliett
______________
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> Perfect sense. In short, the fan cut-in temp. should be somewhat higher
> than the coolant thermostat.
[quoted text clipped - 22 lines]
>> At least that is how I see it! ;-)
>> Does this make sense?

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N8N - 27 Aug 2007 16:26 GMT

I tend to agree, I think the point being made was that *IF* you choose
to use a lower temp fan switch, you MUST install a lower temp
thermostat, or vice versa, otherwise you end up with either large
temperature fluctuations or else a fan that runs nearly constantly.

nate

> What are you all talking about? Re-designing the Porsche already designed
> temperature sensors' settings?
[quoted text clipped - 50 lines]
>
> - Show quoted text -

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