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Car Forum / Jeep / June 2007

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Viscous cabin heater and it's clutch

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stilllearning - 13 Jun 2007 15:51 GMT
Where exactly is the viscous heater clutch located? Is it part of the
A/C clutch?

Where exactly is the viscous heater?

Trying to understand passenger cabin heating:

Normally the coolant heats the cabin, but that happens only after the
coolant heats up (maybe a few minutes after a engine start) and the
thermostat opens up to send fluid to the radiator.

The viscous heater heats the cabin immediately after engine start and
until the coolant is hot.

Why then, in cold weather, if the heater knob is set to high, the
cabin is heated only after a few minutes? Shouldn't the viscous heater
heat the cabin immediately?
stilllearning - 13 Jun 2007 15:52 GMT
> Where exactly is the viscous heater clutch located? Is it part of the
> A/C clutch?
[quoted text clipped - 13 lines]
> cabin is heated only after a few minutes? Shouldn't the viscous heater
> heat the cabin immediately?

Jeep WJ 2004, I6, 4WD.
Mike Romain - 13 Jun 2007 16:05 GMT
>> Where exactly is the viscous heater clutch located? Is it part of the
>> A/C clutch?
[quoted text clipped - 15 lines]
>
> Jeep WJ 2004, I6, 4WD.

OK.......

I'll bite......

The 'viscous' part of the fan is normally the part that causes the
'radiator' fan to freewheel when the engine is cold and to stiffen up
almost solid when the engine heats up so it sucks cold air to cool down
the radiator.

This is a 'gas saving' device apparently saving the gas needed to spin
the fan when the engine is not running hot.  The fan does take several
HP to spin up under load.

Your 'heater' gets it's fluid from the waterpump bypassing the
thermostat so the inside heater core sees warm fluid before the radiator
sees warm fluid.

If you want instant heat, you need to add a circulating block heater
that uses a 'lot' of 120 volt power via an extension cord plugged into
your house to preheat your engine so it doesn't freeze solid and is
easier to start in sub zero weather.  2-3 hours at -20C is usually good
enough for instant heat.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)
SnoMan - 13 Jun 2007 20:34 GMT
>The 'viscous' part of the fan is normally the part that causes the
>'radiator' fan to freewheel when the engine is cold and to stiffen up
>almost solid when the engine heats up so it sucks cold air to cool down
>the radiator.

I can see that you really do not know how these work either. It works
on the theory of a silicone fluid between discs that transfer power
via fluid between them due to shearing forces. The fluid is constantly
pumped out of the "disc" area into a reservior so that is can free
wheel, it starts to engage so to speak when the bi metal coil allows
fluid to return to clutch area and when it is returned at a rate that
exceeds the rate at wheich is it removed at it reaches it sate of
least slippage. It is never a solid or even should be described as
one. The fluid used has been choosen because of its shearing
properties (as rate of shear increases, the power to shear it
increases dramatically unlike motor oil) and for very high resistance
to the tempatures generated by this shearing. It is a old and proven
concept. The amount of torque this design can transfer it limited by
the diameter and amount of clutches and the cooling for them because
the shearing can generate a lot of heat. BTW, when fan engages it also
improves A/C efficency and output (if you have one) as it cools the
refrigerant more before it is expanded again which makes it cooler
when it is expanded. When clutch fans first made their appearance in
the 60's, they were mostly on cars with A/C on them and later were
used on basically all cars by early to mid 70's or so A/C or not

>This is a 'gas saving' device apparently saving the gas needed to spin
>the fan when the engine is not running hot.  The fan does take several
>HP to spin up under load.

Yes it was designed as a gas saving device of sorts and also a way to
allow for increased cooling capacity during times of need and reduce
fan noise when it is is not needed. The only weakness of the design is
too fold, first detriot tends to be conservative with the bi metal
coil setting on some applications lets vehcile get pretty warm some
times and the second is as the mi metal coil ages by nature it will
increase engagement temp and make you think that your clutch fan is
worn out when it may only need a adjustment. As long as the clutch
does not wobble on shaft  and fluid has not leaked out it is likely
still good and may at most need a little tweaking to restore its
operation. I have been tweaking them for many many years and if you
want to know how you can find instructions in link below.

http://forum.snoman.com/viewtopic.php?t=79

-----------------
TheSnoMan.com
Mike Romain - 14 Jun 2007 00:33 GMT
>> The 'viscous' part of the fan is normally the part that causes the
>> 'radiator' fan to freewheel when the engine is cold and to stiffen up
>> almost solid when the engine heats up so it sucks cold air to cool down
>> the radiator.
>
> I can see that you really do not know how these work either.

Once again you have absolutely no clue what you are talking about and
are too stunned to realize it.

Stalking me only proves you are a total idiot!

You have proven beyond any doubt to be a lying Idiot stalker that gives
out advice on a regular basis that will 'kill' people.

Stalking me will 'only' cause you grief and harassment foole.

Once again, Screw off eh.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)
SnoMan - 14 Jun 2007 12:12 GMT
>Once again you have absolutely no clue what you are talking about and
>are too stunned to realize it.
>
>Stalking me only proves you are a total idiot!

As usual, the "troll" is insecure and attacks what he does not
understand in a attempt to make him feel better about his own lack of
knowledge and understanding.

I do not come to NG's to stalk anyone and if it seems I am stalking
you it is because you are basically one of the biggest BS'ers out
there and post a lot of tripe too leaving yourself wide open when you
post things that are not correct. Some people (not trolls like your
self) come to NG's for info while you come for ego. Maybe if you
controled your ego and posted less BS you would find that less of what
you posted would be challanged.

BTW, if I really wanted to stalk you, it would take far more time than
I care to spent in NG's because you seem to post a lot of tripe and I
would not waste my time trying to read and respond to it all.
-----------------
TheSnoMan.com
Roy - 14 Jun 2007 12:27 GMT
>>Once again you have absolutely no clue what you are talking about and
>>are too stunned to realize it.
>>
>>Stalking me only proves you are a total idiot!

At  aadt we refer to him as the "Idiot"

> As usual, the "troll" is insecure and attacks what he does not
> understand in a attempt to make him feel better about his own lack of
> knowledge and understanding.

Thus your most recent post.

> I do not come to NG's to stalk anyone and if it seems I am stalking
> you it is because you are basically one of the biggest BS'ers out
> there and post a lot of tripe too leaving yourself wide open when you
> post things that are not correct.

Well Idiot, you have described yourself and your actions.

>Some people (not trolls like your
> self) come to NG's for info

Hopefully those looking for info will not look to most of the BS you post.

>while you come for ego. Maybe if you
> controled your ego and posted less BS you would find that less of what
> you posted would be challanged.

That is what folks at numerous groups and forums have been trying to get you
to do, STFU

> BTW, if I really wanted to stalk you, it would take far more time than
> I care to spent in NG's because you seem to post a lot of tripe and I
> would not waste my time trying to read and respond to it all.

Hell, why don't YOU respond to the wrong and at time's dangerous stuff you
have posted in various groups over the past year or so?

Let me adjust that sig again for ya.

> -----------------
> TheWrongAnswerMan.com
Mike Romain - 14 Jun 2007 15:19 GMT
>> Once again you have absolutely no clue what you are talking about and
>> are too stunned to realize it.
[quoted text clipped - 4 lines]
> understand in a attempt to make him feel better about his own lack of
> knowledge and understanding.

Once again you have absolutely no clue what you are talking about
because you are too busy stalking my posts and are too stunned to
realize it or even to read the thread.

Enough said....

Mike
Earle Horton - 14 Jun 2007 15:56 GMT
> >> Once again you have absolutely no clue what you are talking
> >> about and are too stunned to realize it.
[quoted text clipped - 8 lines]
> because you are too busy stalking my posts and are too stunned to
> realize it or even to read the thread.

The best place for these types is the killfile.  I have seen enough of
SnoMan's wisdom to last me a long, long time.

Saludos cordiales,

Earle

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stilllearning - 13 Jun 2007 17:54 GMT
> > Where exactly is the viscous heater clutch located? Is it part of the
> > A/C clutch?
[quoted text clipped - 17 lines]
>
> - Show quoted text -

Seems the viscous heater is esoteric enough that googling "viscous
heater clutch" returns no entries! More information on the viscous
heater clutch; here are three relevant pages from the factory service
manual:

http://new.photos.yahoo.com/shahswim/album/576460762403547730
Earle Horton - 13 Jun 2007 21:03 GMT
The text is unreadable, but it looks like an air conditioning refrigerant
compressor.

Saludos cordiales,

Earle

> > > Where exactly is the viscous heater clutch located? Is it part of the
> > > A/C clutch?
[quoted text clipped - 24 lines]
>
> http://new.photos.yahoo.com/shahswim/album/576460762403547730

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Mike Romain - 14 Jun 2007 00:37 GMT
Naw, I could read it.  It is a new toy.  A 'friction' heater for the
coolant to help the inside have warm air faster than if not plugged in
in the winter.

Just something expensive to wear out in my opinion.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)

> The text is unreadable, but it looks like an air conditioning refrigerant
> compressor.
[quoted text clipped - 24 lines]
>>
>> http://new.photos.yahoo.com/shahswim/album/576460762403547730
Mike Romain - 14 Jun 2007 00:35 GMT
>>> Where exactly is the viscous heater clutch located? Is it part of the
>>> A/C clutch?
[quoted text clipped - 18 lines]
>
> http://new.photos.yahoo.com/shahswim/album/576460762403547730

Neat, that's a totally new toy to break down.

I can't say as I really would want one, but it is neat to have an actual
fluid heater for the coolant.  I wonder how many HP it eats up with it's
friction drive?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile...
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)
Earle Horton - 13 Jun 2007 16:37 GMT
This post is incoherent to the point of surrealism.

Unless you use a 120 volt overnight block heater, there is no such thing as
"instant" heat, and there is no "viscous heater".

Saludos cordiales,

Earle

> Where exactly is the viscous heater clutch located? Is it part of the
> A/C clutch?
[quoted text clipped - 13 lines]
> cabin is heated only after a few minutes? Shouldn't the viscous heater
> heat the cabin immediately?

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Matt Macchiarolo - 14 Jun 2007 00:45 GMT
Earle, try clicking on the image thumbnails of the OP's link, it should
bring the images up to readable size. I've never heard of a viscous heater,
but the page does describe it. Kind of a neat idea, it creates heat by
causing friction in silicone fluid inside the V.H. pump. The coolant is
piped through the pump and then into the heater core, which provides quicker
heat to the cabin than would be from getting the engine to operating
temperature.

I would guess the viscous heater clutch is similar to an A/C compressor
clutch.

> This post is incoherent to the point of surrealism.
>
[quoted text clipped - 23 lines]
>> cabin is heated only after a few minutes? Shouldn't the viscous heater
>> heat the cabin immediately?
Earle Horton - 14 Jun 2007 15:01 GMT
What's even more interesting is why the OP is so interested in every nook
and cranny of his Jeep's anatomy.  I recommend putting the factory service
manual on the shelf for a while and driving it to get some real world
experience.

We used to use fuel fired cab heaters in the old air cooled Volkswagens,
especially the vans.  I believe that tractor trailers use something similar.
The main problem is that they are dangerous and finicky if not maintained
properly.  That usually consists of cleaning and adjusting a spark gap.

Saludos cordiales,

Earle

> Earle, try clicking on the image thumbnails of the OP's link, it should
> bring the images up to readable size. I've never heard of a viscous heater,
[quoted text clipped - 34 lines]
> >> cabin is heated only after a few minutes? Shouldn't the viscous heater
> >> heat the cabin immediately?

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stilllearning - 14 Jun 2007 16:19 GMT
> What's even more interesting is why the OP is so interested in every nook
> and cranny of his Jeep's anatomy.  I recommend putting the factory service
[quoted text clipped - 58 lines]
>
> - Show quoted text -

Why am I interested in supposedly useless information?

(1) I find the engine innards fascinating. I am amazed at how human
innovativeness has created such a beautiful,  intricate and harmonious
machine which just about all of us take for granted. The automatic
transmission is about the most complex and ingenious machine I know.

(2) I plan to overhaul my engine in due course. I must know every
insignificant object under the hood, know exactly why it is required
and how it works. I plan to absorb everything in the service manual -
all the thousands of pages. Don't laugh - eventually I plan to
overhaul the automatic transmission.

(3) I have already done some service myself - I plan to do most, if
not all of it. I need all the information I can get.

I hope in the process others also gain appreciation and insight into
their vehicles.
reboot - 14 Jun 2007 03:29 GMT
>Where exactly is the viscous heater clutch located? Is it part of the
>A/C clutch?
[quoted text clipped - 13 lines]
>cabin is heated only after a few minutes? Shouldn't the viscous heater
>heat the cabin immediately?

Denso produces the viscous heater used on the VM Diesel that Chrysler
installs in KJ's.  The operating principle is the same as a viscous
fan drive but instead of dumping slip heat to the airstream via the
fins on the outside of the fan drive, it transfers this heat to the
engine coolant.  A clutch much like used on an AC compressor is used
to switch the heater on and off.

The power consumption is in the range of a few horsepower (3-5 ?)
depending on engine RPM.  They use these on high efficiency diesel
engines (CRD) which don't warm up very fast in cold weather.  These
efficient engines will also fail to maintain coolant temperature in
low speed driving and while idling - leading to complaints that the
heater isn't working correctly.  So they switch the viscous heater on
in these conditions too.

This is a less expensive solution than using a PTC (positive
temperature coefficient) electric heater in the HVAC.  PTC heaters are
in the 1kW to 1.5kW range so at 12 - 14 VDC they're pulling a hell of
a lot of amperes and the alternators, batteries and of course the
wiring are all upgraded.  

PTC heaters warm the air immediately because they are directly in the
air stream in the HVAC.  Viscous heaters are slower because a portion
of the heat is lost in the block and head.  Even so they are a big
improvement over no supplemental heating.

In Europe they also use fuel fired heaters (Webasto is a well known
name) but these are real expensive and add a lot of complexity.

reboot

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