From: mark on
On Feb 4, 9:40 pm, Hachiroku ハチロク <Tru...(a)e86.GTS> wrote:
> On Thu, 04 Feb 2010 17:34:39 -0800, mark wrote:
> > On Feb 4, 9:26 pm, twisted <thenited...(a)yahoo.com> wrote:
> >> On Feb 4, 8:15 pm, mark <markha...(a)hotmail.com> wrote:
>
> >> > I am building an airboat and have an old 350 chev. in it. It
> >> > originally had a clutch fan on it. I want to hook up an electric fan
> >> > that will turn on when the radiator gets hot and off when not needed.
> >> > Does anyone know what vehicle would have a fan switch with 3/8" NPT
> >> > pipe thread as this would thread into the chev. thermostat housing (I
> >> > assume this is where I should put it). I could use adapters if needed.
> >> > My local auto parts stores can't look up this info, they just want the
> >> > year make and model of vehicle. I already have everything wired with a
> >> > relay and the auto parts guy gave me what I think is a temp. sending
> >> > unit. I want something that is open when cool and grounds when temp is
> >> > hot. Thanks
>
> >>http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Co...
>
> > That is exacty what the guy at the parts store sold me. I ran the engine
> > today for 10 minutes and the rad got too hot to touch, (cap off) and the
> > fan did not turn on, I pulled the wire off the sensor and grounded it to
> > the block and it ran fine. Is it just not hot enough? What temp. do these
> > switches typically trip at? Thanks
>
> You either have a bad switch or a bad ground!
> The switch should trip about 200 degrees F.
> If the fan ran when it was grounded, then run a lug from the base of the
> switch to a good ground, or right to the engine, or try another switch.
>
> On way to test the switch is to fill a pan with just enough water to cover
> the sensor end, attach an ohmmeter to the leads, and boil the water. If
> the ohmmeter doesn't go to about 3-4 ohms or less when the water's
> boiling, you need another switch.- Hide quoted text -
>
> - Show quoted text -

The ground must be good because the fan will run if I ground the wire
to the outer body of the switch. I will try running with the cap on so
the temp. will raise higher and I will also test the switch as you
said. Would testing for continuity betweeen switch terminal and body
at boiling temp. also tell me if it is working?
From: twisted on

> >http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Co...


Bad link.
From: mark on
On Feb 4, 11:57pm, twisted <thenited...(a)yahoo.com> wrote:
> > >http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Co....
>
> Bad link.

The switch would not close in boiling water so I went to return it,
the guy said it was rated to close at 220 and to test it with a
propane torch. I tried that and it works. So now I am wondering if
that seems high? Doesn't this mean that all the water in the system
will reach 220 before the fan will turn on even though the thermostat
will open at 195?
From: Paul on
mark wrote:
> On Feb 4, 11:57 pm, twisted <thenited...(a)yahoo.com> wrote:
>>>> http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Co...
>> Bad link.
>
> The switch would not close in boiling water so I went to return it,
> the guy said it was rated to close at 220 and to test it with a
> propane torch. I tried that and it works. So now I am wondering if
> that seems high? Doesn't this mean that all the water in the system
> will reach 220 before the fan will turn on even though the thermostat
> will open at 195?

There are different temp sensors. Not all are the same.
It sounds like that one is meant for fan #2.
That fan typically turns on around 224F.
From: jim on


mark wrote:

> On Feb 4, 11:57 pm, twisted <thenited...(a)yahoo.com> wrote:
> > > >http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Co...
> >
> > Bad link.
>
> The switch would not close in boiling water so I went to return it,
> the guy said it was rated to close at 220 and to test it with a
> propane torch. I tried that and it works. So now I am wondering if
> that seems high? Doesn't this mean that all the water in the system
> will reach 220 before the fan will turn on even though the thermostat
> will open at 195?

No, it means (if the switch is at the thermostat housing) the water leaving the
engine is at 220F. Hopefully, the water entering the waterpump is cooler and the
water in the water jacket is at a temperature somewhere in between the inlet and
outlet temps. Ideally most of the time there would be enough cooling that the
fan would stay off and when it does kick on it would run for only a short while
and then shut off. Using a switch at a lower temp isn't going to help much if
the fan and radiator aren't able to keep up at this setting. Also make sure the
switch and wiring are rated heavy enough to handle the maximum current for the
fan.

-jim