The "pump too fast lose less heat” notion is very popular and many experienced mechanics are very attached to it but – it is a fallacy. Davies Craig has been carrying out research and development for over a decade on a number of projects and has never been able to pump genuine liquid coolant faster and lose less heat. In all car engines, when the mechanical pump reaches cavitation speed, coolant turns into a gaseous state which is compressible,(liquid is not) and the real flow rate of liquid coolant drops even though the mechanical pump has a higher rpm, and so heat loss drops. The engine temp then rises. And it only seems like the flow rate is too fast, and the coolant is spending too little time in the radiator to lose its heat etc. etc..

The ideal operating engine temperature is dependent on the type, size, capacity, workload and environment the engine is working in, however the best engine temperature is usually between 85-105°C or 185°F-221°F.

Generally when the fuse holder is melting it indicates that either the wiring loom used between the fan and the switch or relay is an incorrect gauge or the motor on the fan may have an internal fault. If you have used a smaller fan than a Davies Craig 16" Fan or you have used a different brand fan before fitting the Davies Craig 16" Fan and you are using the previous fans wiring then this wiring may not be the correct gauge to carry the current our 16" fan produces. The Davies Craig 16" Fan is the only fan in our range that has a heavier gauge wiring loom than the others as it produces a lot more current than the others and requires heavier gauge wiring so the wiring doesn't overheat.

As for the fuse blowing when you use the A/C switch, this either indicates the use of an incorrect fuse or maybe an internal fault with the electric motor. You should be using a 30amp fuse in the wiring loom from the 16" Fan Kit and a 25amp supplied fuse in the wiring from the Electronic Controller.

This EBP has its own built in voltage regulator to regulate & smooth the input voltage. As you mentioned earlier that the customer is using a AC to DC transformer & a bridging rectifier circuit, indeed he need to use an appropriate capacitor. I cannot give you any values for the capacitor which he need unless I see the full circuit. But as an example if he is using a bridge rectifier of 1N4148 then 220uf capacitor will do the job.

A customer was happy to share the process they used to connect a 3/4" pump hose to a 35mm radiator hose.

From the left to right, there is a barbed fitting for a 1 1/4 " hose w/ threaded female connector (the 1 1/4 is close enough to 35mm). Next is is a threaded 1 1/4" male fitting, with the other end being a 1 1/4" slip fitting. I will glue into that a bushing, 1 1/4" male by 3/4" threaded female. Finally I will screw in a 3/4 inch threaded/barbed connector, which will fit into the pump hose.

Let us give you some information on the function of the radiator pressure vent.

When the coolant or water gets hot it expands this results in a pressure increase another cause of pressure increase comes from the water pump (mechanical or electric).

The vent pressure rating is determined by several factors:

1. Pressure caused by the hot coolant at normal/slightly above normal operating temp
2. The pressure (resistance to flow) caused by the water pump and the components in the system (i.e. the radiator)
3. The Maximum safe pressure of all components plus a safety factor

When the coolant pressure and pump pressure are added together you get the total system pressure.

When the pressure is high enough it opens the pressure vent valve and coolant is allowed to escape the system (overflow) to reduce pressure.

In most cooling systems this coolant isn’t lost but stored in an overflow bottle/tank.

When the pressure drops a vacuum is created. The radiator cap also has a vacuum relief valve. When the pressure/temperate is reduced and vacuum relief valve opens to prevent a vacuum forming.

When this happens the coolant that is in the overflow bottle is sucked back into the cooling system to keep the system full. If there is not an overflow system installed air will be sucked into the system.

So, your problem is that the added pressure (resistance to flow) from your new radiator and upgraded components, when added to the pressure form expanding coolant is causing the system to vent. If you have a correctly installed overflow system and you’re not losing coolant and able to maintain temperature then there is no real problem. However, if the system is venting lots of coolant regularly then you may need to get a higher rated pressure cap.

If you don’t have an overflow or expansion tanks system installed then I recommend installing one. After this you can look at the pressure rating of the radiator cap.

If the current cap is only venting when well above (5C+) the target/ operating temp then you shouldn’t need a new cap. If the cap is venting at operating temp or slightly above (less than 5C) then a higher rated cap may be needed.

Whilst all 3 can be measured as a pressure value, they are not interchangeable. Understanding the difference between them is critical to getting the most out of your Electric Water Pump

System Pressure is the measure of how much the coolant has expanded due to the increase in temperature, this is important because as pressure increases, so does the boiling point of your coolant. it is also very important that the system pressure does not exceed the max pressure rating of components to prevent damage. in a typical automotive cooling system this is done by the radiator pressure cap.

Head pressure is the measure of how much energy a pump can impart into the coolant. This pressure is not the same as System Pressure as it is the differential pressure between the inlet and outlet of the pump. Head Pressure can also be called Head Height, basically the maximum vertical distance the pump can pump a fluid.

Pressure Drop or System Resistance is simply the measure of how much energy (Head Pressure) is required to move coolant though the system at a given flowrate. The System Resistance is often shown in the System Curve this curve shows the Head pressure required for any given flowrate,

Whilst the 3 values are not interchangeable, they are all equally important when selecting the right pump for your application, the System Resistance and Head Pressure are used to find a suitable pump, while the system pressure is determined by the maximum pressure the pump can withstand without damage.

The following relates to possible causes should this unit give off a false alarm

• Check that the coolant level in the radiator and that the top hose is full.
• Turbulence in the top hose which could be caused by bend and/or elbows?
• Sensor wires may be damaged and shorting out.
• Check ignition source could have a bad connection. This is very common when the ignition source is shared with the coils, or other high load components.
• The Float Sensor is no longer switching on.
• The Float Sensor may be subject to wear.
• The control unit is faulty.
• The Float Sensor is installed upside down or at the incorrect angle.
• The Float Sensor wires from the In-Line Adaptor should be in the 12 o’clock position.
• Poor Float Sensor location.
• The Flow Sensor’s Float must be in the bottom position of the shaft for at least 30 seconds before the alarm will sound.

To test the Float Sensor, you will need to check the continuity when the float is in the “full” position.

This should show an Open circuit, if you are getting a closed circuit or continuity then the sensor needs replacing.