Water temperature gauge wiring diagram, for the Rotax 582, and Rotax 618 aircraft engines.

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Water temperature gauge wiring diagram

Proper Water temperature gauge installation.

In 1984, Rotax introduced the liquid cooled engine into it's aircraft engine line, the 532 Rotax which was later updated to the 582. Both the  532 and 582 uses a 50/50 mixture of Glycol (antifreeze) and distilled water.

Note: While this is the recommended mixture - for COLD climates - in warmer climates or seasons - mixtures of 10% anti freeze to 90% distilled water can be used. This will aid in lowering coolant temperatures - anti-freeze is NOT an effective coolant! It is used to prevent freezing and supply lubrication to the system. 

My experience has shown that a mixture of 10% antifreeze can drop temperatures as much as 30 degrees versus 50% - in some applications.

Do not use tap water - garden hose water - or water from a water softener! 
The chemicals in water will cause corrosion of the internal metal parts. 

The use of any water other than distilled will cause deposits to form that can prevent the transfer of heat from the cylinder to the water jacket. Liquid cooled engines like their air cooled counter parts require temperature gauges to monitor the temperature of the liquid in the cylinder head and cooling system.

A water temperature gauge when properly installed and located, can accurately measure the temperature of the coolant, so as to prevent serious internal problems, and help prevent over heating and or cold seizure.

Water temperature gauges use a thermistor - a resistor that varies its resistance according to the temperature of the liquid in the cooling system and engine. The two styles of gauges that I am familiar with both require an external power supply. This provides the necessary 6 to 12 volts required to operate the gauge. 

The water temperature range should be between 140'F and 180'F (60'C and 8O'C) with the maximum being 20O F (95'C). One thing to note is that initially a high reading may start going down due to a low coolant level, because the fluid is escaping and thus  is not reaching the sending unit, (which should be located in the center of the cylinder head) will then indicate a LOW temperature reading!! 

While blockage in the coolant flow or air flow system,  will indicate a  higher temperature. 

To install the water temperature gauge and sender, connect the wire from pin #4 of the gauge to the ignition switch or other 12V source. The wire from pin #5 is grounded. Connect one of the wires from the sender  to the wire from pin #2 of the gauge. The other wire of the sender is grounded. The sender has no polarity thus it does not matter which sender wire is attached where. 

Route all wires away from the hot manifold and other pipes. Tie the wires to other wire bundles, if they are available, and support the wires at 12" to 15' intervals. When going through to metal firewalls etc. use rubber grommets to prevent the metal from tearing the wire.

Why a water temperature gauge - to help prevent "Cold Seizure"!

Cold Seizure

This is probably the most reported problem that occurs on a 532/582 Rotax liquid cooled engine. In many cases the pilot doesn't even know that he has had a cold seizure! So what is it and how does it happen? Remember this is a liquid cooled engine (cold seizures also occur on air cooled engines and for the same reason). Here is an example of a situation in which a cold seizure could occur.

A pilot flying on skis is sitting at the end of a runway, impatiently waiting for traffic to land and clear off the runway. During this time his engines has been idling. The runway is finally clear and he applies full power and takes off , about two thirds of the way down the runway and about 500 feet in the air the engine suddenly quits. The pilot is forced to make an emergency landing. Once down on the ground the engine starts and runs again.

At this point the pilot will usually do one of two things, try to find out why the engine quite - or start the engine and try another take off.

What has happened is that the engine coolant has been cooling in the rad, in winter in cold temperatures, this can mean that the temperature is down below 100 degrees F. The engine on the other hand is under load and is creating heat, the pistons are expanding. As the cold liquid enters the area around the cylinders, the cylinder shrink and this causes a cold seizure.

The problem is that cold seizures in most cases seizure only a part of the ring. This allows enough compression for the engine to continue to run. One of the first things pilots will notice after a cold seizure is that they generally cannot achieve full rpm on run up and climb out. In one case over a 50 hour period a pilot repitched his prop 4 times to a finer pitch, and dejetted his carbs down to 148 main jets from 165's before calling for help.

The use of adjustable radiators, thermostats, proper flow rates , the use of EGT gauges, and water temperature gauges, and proper pilot take off and landing procedures all help in eliminating Cold Seizures.
What can happen when an engine has a cold seizure.

Visit a crash site.

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Water Temperature Gauge Wiring Diagram

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