In a message dated 4/4/2003 10:31:04 PM Eastern Standard Time,
MotoPsyche@aol.com writes:
> do you use a thermostatic switch
> to control the fan, or did you hook up a manual on/off switch
A thermo switch is much better since it is automatic. Get a hot light switch
from a GM or Ford car ( most any year from 60's to recent ) Chryslers have
always ( at least back to 55) had temp gauges so that sensor won't work.
The GM switch you want has a 1/4 tab for a wire and a small ( 3/32) hole
covered with paint. Scrape the paint from the hole and you will find a
slotted screw. Turning the screw clockwise will cause the switch to come on
at a lower temperature.
The Ford switch has a threaded wire terminal with either a slot on top or
flats. Turning the screw clockwise will lower the turn on temp.
Use this switch to ground the coil of a relay. The Bosch cube relays are
just great for this since they have 1/4 pushon terminals. Be sure to get a
good one though, many places sell junk copies.
The other end of the coil needs switched 12V+ if you want the fan to run only
when the key is on. Use constant battery power if you want the fan to run
with a hot motor that is shut off. This trick can reduce fuel boilover after
a hard run. If your battery is any good this won't be a problem.
One contact of the relay goes to the + side of the fan. ( use contacts that
are normaly open) The other contact goes to a fuse then to constant battery
power. Place the fuse ( or a fusible link) as close to the battery as
possible.
The temp sensor can be threaded into most any water jacket though a block
drain is probably the least desirable location.
Turn the temp screw a couple of turns clockwise then experiment a bit.
A second switch like this can be a great early warning light. I added one to
my 77 Chevy truck. The factory gauges are still intact but don't catch your
eye like a light.( the light is even integrated in to the existing warning
cluster, also added a oil light as well.)
The switch does not turn on in normal driving. During a long uphill pull ( 3
miles) towing a box trailer the light will turn on at the top. Also after a
highway run the light will be on for a min on a hot restart. With this setup
a small loss of cooling capacity will be noticed long before any damage is
done.
All this stuff can be made from junkyard parts for $ 5 - 10.
Harold
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