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Derale Dual-Fan Adjustable Fan-Control Thermostat with Thread-In Radiator Probe

Derale Dual-Fan Adjustable Fan-Control Thermostat with Thread-In Radiator Probe

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Automatically control your electric radiator fan(s) with this adjustable, thermostatic switch. Set the turn-on temperature anywhere between 150 F and 240 F, and the power-saving shut-off falls just 10 degrees below. Call 800-298-1624 to order Derale accessories and parts part number D16789 or order online at etrailer.com. Free expert support on all Derale products. Guaranteed Lowest Price and Fastest Shipping for Derale Dual-Fan Adjustable Fan-Control Thermostat with Thread-In Radiator Probe. Accessories and Parts reviews from real customers.
  • All Info
  • Reviews (5)
  • Q & A (6)
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  • Why etrailer?

Derale Accessories and Parts

  • Radiator Fans
  • Thermostat
  • Derale
  • 35 Amps

Automatically control your electric radiator fan(s) with this adjustable, thermostatic switch. Set the turn-on temperature anywhere between 150 F and 240 F, and the power-saving shut-off falls just 10 degrees below.


  • Provides necessary airflow for sufficient cooling by switching on radiator fan(s) when fluid reaches pre-set temperature
    • Temperature setting is user determined and may be set anywhere between 150 F and 240 F
  • Designed for use with dual, electric radiator fans or Derale high-output, single fans with 2-speed applications
  • Conserves power by turning off fan if fluid falls below determined shut-off temperature
  • Comes with circuit breaker and air conditioner override circuit
    • AC override engages the fan automatically whenever the air conditioner is turned on to help compensate for increased engine load
    • Circuit breaker automatically resets - no more replacing fuses
  • Housed in finned, die-cast aluminum casing
  • Includes removable, thread-in radiator probe and installation kit
  • Made in USA


  • Probe: 3/8" NPT
  • Adjustable temperature range: 150 F - 240 F
  • Maximum capacity: 35 amps
  • 1-Year warranty

16789 Derale Adjustable Dual-Fan Control Thermostat - Thread-In Probe

Item # D16789

Installation Details D16789 Installation instructions

Customer Reviews

Derale Dual-Fan Adjustable Fan-Control Thermostat with Thread-In Radiator Probe - D16789

Average Customer Rating:  4.6 out of 5 stars   (5 Customer Reviews)

Automatically control your electric radiator fan(s) with this adjustable, thermostatic switch. Set the turn-on temperature anywhere between 150 F and 240 F, and the power-saving shut-off falls just 10 degrees below.

- D16789

Nice dual fan controller. About the only one on the market that will take care of 2 fans at 25 amps each. I installed Derale dual fan assembly 16927. This is my second controller D16789. Had the first one 3 years and it did just fine until I shorted it out by accident. Very pleased with it. Rec'd this one promptly as I have all my orders from etrailer. The quality is always great. I have a class 5 trailer hitch and load leveling system. All work well and still look great after 3 years. Thanks again George J and etrailer for quality products!

- D16789

Product shipped quickly and cheaper than everywhere else. Shipping was also cheaper. Customer service emailed me throughout the whole transaction keeping me informed of the progress. etrailer was a pleasure to do business with. etrailer.com can look forward to my future business.

The 16789 Derale Adjustable Dual-Fan Control Thermostat - Thread-In Probe, does the thread in probe go into where the drain plug would be on the radiator? Mine is on the drivers side bottom facing the engine. 1970 Monte Carlo. That would be the only threaded hole I have on my radiator. Thank you for your help.
-- comment by: Tony F - 09/09/2013

The probe has 3/8 NPT threads. If your radiator drain plug has a 3/8 NPT it could certainly go there. There may be burp or test/fill caps elsewhere in the system that match a 3/8 NPT threading that could be used. Just keep in mind where you are installing the probe in relation to the other components of the coolant system. Do you want to operate the fan by the temperature of the coolant before or after it passes through the radiator? Just something to think about if you have not already.

-- Etrailer Expert Patrick B - 9/13/2013

- D16789

I also ran into a problem with trying to find somewhere to tap into the block for the thermostat so I had to call Derale and order another part that I had to get from different vendor. it was a push through rod that went into the fins of the radiator. It works but I had a hard time trying to get adjusted for the right temperature. I found that with the way that I have it set up, I used the optional wire and ran it to a switch, this allows me to turn the fan on till the motor had ran for awhile and heats up the rod. if I where to let it turn on by itself it would over heat before the first fan would turn on. But with that said the controller with the 2 fan set up is the only way to go.

- D16789

I highly recommend this Derale Dual Fan Thermostat Control. I also recommend the Derale Dual Fans. I have installed them on a 6.0 Chevy Avalanche and I eliminated the clutch fan. I live in South Texas and the temperature this summer has been over 100 every day all summer long. This combo has worked flawlessly and never got over the temperature it was set on. I drive about 300 miles daily. HIGHLY RECOMMENDED!!!

- D16789

Great product! Meets expectations and functions as described. It was a great experience ordering from etrailer. They are very quick to ship and they are great at communicating. Thanks for the quick work and good effort. Pictures coming soon!


Ask the Experts about this Derale Accessories and Parts

  • Speed Shut Off of Derale Adjustable Fan-Control Thermostat # D16789
    The Derale Adjustable Fan Control Thermostat you referenced, part # D16789 will not shut off at a certain vehicle speed, but at an adjustable fluid temperature. The temperature at which the fan turns on is adjustable between 150-240 degrees Fahrenheit. The fan automatically shuts off once the fluid cools by 10 degrees. So, say you set the thermostat to turn the fan on once the coolant reaches 190 degrees. At 190, it would turn on and run until the coolant reached 180 degrees.
    view full answer...
  • Solution For 2008 GMC Sierra 1500 5.3L Overheating When Towing 4,000 lb Trailer Up a Grade
    If you are pulling a trailer under the towing capacities of your 2008 GMC Sierra 1500, the engine temperature of the truck should not overheat. I would recommend having the vehicle looked over by your GMC dealership. What I would recommend is adding a combination transmission and oil cooler, as well as a cooling fan. This will cool the transmission fluid, the engine oil, and engine. For this, I would recommend the Derale Combination Transmission and Engine Oil Cooler, part # D15903....
    view full answer...
  • Is Derale Dual Electric Radiator Fan A Variable Speed
    The Derale Dual High-Output, Electric Radiator Fan, part # D16825, is a single speed system and both fans operate at the same time. There are options available for control of the fans you may be interested in. The first is to use a switch like the Derale Lighted On/Off Switch, part # D16740. This switch is a simple toggle switch that allows you to easily turn your fans on or off. If you wish to install an automatic system, I recommend part # D16789. This will turn the fan on or...
    view full answer...
  • Fan Recommendation for a 1979 Ford F150 with a 460 Cubic Inch Engine
    As long as you have the clearance, the Derale Radiator Fans # D16826 that you referenced would be a good choice for your 1979 Ford with a 460 cubic inch motor. This unit can pull up to 4,000 cfm and should work well for cooling your vehicle. I attached a picture that shows the dimensions of this setup for you to compare with the size of your radiator. You might also be interested in purchasing a Derale Dual-Fan Adjustable Fan-Control Thermostat # D16789 to allow you to select when...
    view full answer...
    Image 1 for
  • How Does Derale Adjustable Fan-Control Thermostat with Thread-In Radiator Probe # D16789 Wire
    You'll want to also get the Derale Dual-Fan Adjustable Fan-Control Thermostat with Thread-In Radiator Probe # D16789 to wire up the Derale Hyper-Cool Extreme Remote Cooler Assembly w/ Fan # D15876 that you referenced. The fan of the kit you mentioned just has a power and ground wire so you'll need the controller to tell the fan when it needs to come on and off. If you check out the attached install instructions for the # D16789 you'll see how to wire it to the fan and install the probe.
    view full answer...
  • Thermostat Recommendation for Use with Derale 27" Dual High-Output, Electric Radiator Fan
    The Derale 27" Dual High-Output, Electric Radiator Fan-and-Shroud Assembly # D16837 that you referenced does not come with wiring but with a thermostat kit like the # D16789 you'd be set. This can control both of the fans and wire in to the AC system too if needed.
    view full answer...

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Info for this part was:

Employee Mike L
Expert Research:
Mike L
Employee DeAnne T
Updated by:
DeAnne T
Employee Daron K
Updated by:
Daron K

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