Danspeed1

Hey guys,

Just picked up a Derale 180*F Thermostatic Fan Switch, the one that screws into the block in place of the old 220*F switch, to install into my 89 Vette. Only problem is I noticed that the old switch has one wire leading out of it and the new one has two wires??? Is one of those two wires a ground or something?? I am not installing the wiring harness that comes with the kit, just replacing the sensor/thermostatic switch. Anyone know about this?

DG

Slalom4me

These instructions are for the 16738 with the push-in probe,
but I expect that wiring for the 16739 w/ the "3/8" NPT water jacket
thread-in probe" is essentially the same.

16738 Single Stage Electric Fan Thermostat Installation Instructions

The Derale Thermostat switch is shown with an external or isolated
ground, it does not ground to the body of the switch.

In the wiring diagram provided above, Yellow is switched 12+VDC and
Brown goes to the relay and then to ground through the Black wire.
When the Thermostat activation point is reached, the internal switch
closes, completing the path, energizing the relay and thus closing the
circuit for the fan motor.

My vote is that your OEM switch receives 12+VDC from the OEM relay and
grounds internally to the cyl head. In this case, the Derale switch can
be used as a replacement by connecting your OEM wire (12+VDC) to
the Derale Yellow and then connecting the Derale Brown to a suitable
ground. When the Derale switch activates, current will flow from the
OEM relay to ground, closing the OEM relay circuit for the fan motor.

Or do you have this model?
IN – LINE FAN THERMOSTAT SWITCH INSTRUCTION

.

_twisted_

Not for nothing, but that Derale switch your using was intended for use in a trans/oil cooler - if it is the one SLalom mentioned

Slalom4me

I provided two links.

The first link refers to two variations of fan switches for engine coolant
radiators: one with a sensor probe that is inserted between the fins of
the radiator, the other with an immersion-style probe intended for installation
in a port in the coolant passage.

The second link is for a switch with two wires and an AN fitting for
mounting in-line. The switch is indifferent to the liquid it is sensing.
It will close/open the circuit at the activation temp, regardless of
whether lubricant or coolant is in the line.

.

Danspeed1

Slalom,

Thanks for the in-depth description of how to install the coolant switch. It installed and wired up in minutes... worked very well.

Thanks again,

Dan

Slalom4me

Happy to hear that everything turned out well. Just paying it forward.

In case you become interested in a higher activation point down the
road, Echlin "Coolant (Thermo) Fan Switches" with various activation
temps are (or were) available from NAPA as follows:

ON ............... OFF .... P/N#
204-220º ....... N/L -- FS113
213-229º ....... N/L -- FS112
224-236º ....... 212º - FS110
229-245º ....... N/L -- FS111

These are physically similar to the OEM switch. They take one wire
and ground to the head. Thread is 3/8" x 18 NPTF.

.

BerniesVette

Will this switch work on my LT1 located on the driver's side block area? I have one lying around, and if it will work, I can postpone having a chip burned until I make some other mods.
Bernie

BADDUCK

The only comment I have is that seems a low ON temp. What is the off temp? It sounds like your aux fan will run pretty much all summer. BTW I run a 200* on 185* off on my '89 with a 170* stat.

Slalom4me

My vote is that the part on your LT1 is a sensor, rather than a switch.
Thus, no.

.

Danspeed1

Pretty much.... this is just supposed to sufice till I can find a way to get the fan programmed cheap or afford to have the pcm tuned. I hate to pay $175 just to get the fans turned on sooner... I would like to get the car tuned but at $3.05 for regular and $3.25 for super.... I really don't want to have the car tuned from 93 just yet. plus the vettes getting 25+ MPG on good days (or rather days I stay off the pedal). This is just a quick fix for the problem.

DG