Thermatic Fans

From Holdenpaedia
Jump to: navigation, search

Page created by ReaperHR 

Back to Cooling

Relay suitable for powering Thermo Fans. Photo by HQDan.

Thermatic Fans:

What Is A Thermatic Fan:

A Thermatic Fan is an Electric Fan that is powered by the Car's Battery turned on by a Temperature Sensitive Switch. 


This page is created and researched by third parties completely unrelated to the company Davies, Craig. Davies, Craig at no time has had any input into this or related pages in the Holdenpaedia or Work Guides other than to lend assistance when required and supply the products. Davies, Craig is not currently and never previously been a sponsor of, nor asked for the guides/pages to be done. These pages and guides were all done by myself for my own interest and to try and curb some of the lies and BS that is on the net by parties with little to no current understanding or experience with these products. They were done to help interested members of the community see what is involved in installing these products and what they are capable of doing. At no time did Davies, Craig approach me and ask or pay for these pages to be done and at no time did they influence any of the results or comments. ReaperHR (Greg)
Relay suitable for powering Thermo Fans. Photo by HQDan.

   By ReaperHR

A Davies, Craig 16" Thermatic Fan

Advantages of Thermatic Fans:

A standard steel bladed fan is efficient at dragging air through the radiator and blowing it onto the engine thereby cooling it. It is however inefficient at detecting just how much air is required to do its job (being in effect a belt driven item mounted to the water pump). For the sake of this page the Thermatic Fan being referred to is one that is produced by an Australian company called Davies, Craig Pty Ltd.   


As a possible modification to your Holden the Davies Craig Thermatic Fans are a popular item amongst owners of old Holdens whether they be performance cars or daily drivers. Thermatic fans have been used on newer cars for many years and are an accepted component on modern vehicles due to their use giving improvements in performance and economy. Therefore the thermatic fan is a cheap and effective way to bring your classic car into the 21st century (without changing your name to Buck Rogers).  Image by T.  Thermatic fans can be used to replace or assist standard belt driven fans and dependant on space can be installed infront or behind of the radiator. Many of the larger old holdens used adaptor plates to force their standard fan closer to the radiator as an easy method to get better cooling. With this in mind it is worth noting that the thermatic fans actually sit flush with the radiator, forcing or drawing air through the radiator at a much more efficient level.

If the thermatic fan is used to supplement the current fan then the driver can expect a constant flow of air through the radiator no matter what speed the vehicle is driving (or more precisely, what revs the motor is running at). But the thermatic fans truly stand out when used as the primary cooling device and the Davies Craig site mentions the following advantages in relation to using their thermatic fans:
A Davies, Craig 16" Thermatic Fan installed into a HR Holden behind the grill
 Advantages to using Davies, Craig Thermatic Fans:
 Economical replacement for failed original parts
 5-10% increase in engine power and fuel economy over conventional fans
 Reversible blades for ‘pusher’(upstream) and ‘puller’(downstream) applications.
 Compatibilty with all electric fan controls
 Coverage for a wide variety of applications
  When used to replace the standard water pump mounted fan and used with a thermatic fan controller, the thermatic fan will only activate once the temperature reaches a level selected by the owner through the controller. With multiple fans the owner can have them activating at different temperatures, for instance as the car reaches optimal temperature and as it reaches 10 degrees above it. The fans, once activated, will push an amount of air equivalent to driving at speed, and so are ideal for situations like stop/start traffic, traffic jams, extremely hot days etc
Thermatic Fan Controller and parts from Davies, Craig


Thermatic fans work by accepting a standard input voltage (12V or 24V) which enables the fan to spin at full speed. In conjunction with a temperature sensor and controller the thermatic fan is switched on once a preselected temperature is reached, and off once the temperature returns below that level. This means that if the car is sitting for long periods idling the thermatic fan may switch on to cool the car and after a period of time switch itself back off once its job is done. This information generates another bonus to thermatic fans, if plugged straight into a source voltage like the battery instead of running through the ignition the thermatic fan will continue to run after the car is switched off, and will therefore continue to cool the motor. It will unfortunately not cool the coolant like it would if the coolant was flowing but if used in conjunction with the Davies, Craig Electric Water Pump (and the pump is wired to a turbo timer) the cars entire cooling system will continue to run after the car is shut off avoiding heat soak and preventing damage to the motor.
Without Thermatic Fan
 With Thermatic Fan
 In the morning you start your car, the fan immediately starts cooling your motor even though it is still cold.  In the morning you start your car, thermatic fan doesn't activate and remains off until the temperature reaches a level the owner has specified through adjustments to the controller. This enables the car to warm up quicker.
 Your car is now up to operating temperature, the thermostat slowly opens and coolant begins to flow, the standard fan is now cooling the flowing coolant at a level dependant upon the revs of the motor. Your car gets up to operating temperature, the thermatic fan may or may not have activated yet depending on your settings.
 You hit a traffic jam, or a heap of traffic lights, your car continues to idle but there is little air flowing through the radiator to cool the coolant due to the slow speed of the fan, your temperature starts to rise. You hit a traffic jam, or a heap of traffic lights, your car continues to idle but there is little air flowing through the radiator to cool the coolant, however once the temperature reaches the level you have specified the thermatic fan switches on. Your motor is now getting air flow like it was driving on the highway instead of stopped. Your temperature will be held at the perfect operating temperature instead of spiraling out of control.
 You finally get home with your overheated motor and shut it off, there is now no flow of air and the coolant rapidly fails to do anything as it sits still in the motor and begins to heat up, now rather than cooling your motor it is maintaining the heat that is in it. The motor will actually gain heat even though it is no longer running due to the lack of coolant and air flow. You get home with your motor that is still sitting at ideal operating temperature and switch it off. Now if you have your thermatic fans directly wired to battery power they will occasionally turn on to keep your engine at or below ideal temperature. The coolant is not flowing but the thermatic fans will supply air flow over the motor allowing it to cool better. If used in conjunction with an EWP and turbo timer the entire system will still be working like the car was running and will take excellent care of the cooling of your vehicle while you sit down with a beer to watch the footy.



Fan Braking

EL Falcon Fans Fletch Newbury's Shed



Back to Cooling