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Thermoswitch Replacement
 
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Pelican Technical Article:

Thermoswitch Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$100

Talent:

**

Tools:

19mm deep socket

Applicable Models:

Porsche 944 Turbo (1986-89)

Parts Required:

Thermoswitch

Hot Tip:

Be prepared for spilled coolant

Performance Gain:

Proper working fans

Complementary Modification:

Flush coolant system

The thermoswitch or coolant temperature sensor on the Porsche 951 determines the temperature of the coolant and sends a signal that works with the radiator fans and the turbo coolant pump. If you are having trouble with an erratic turbo pump or fans or they are not coming on, one of the first things you should check is the thermoswitch.

To replace the switch you will need to drain the coolant level to below the thermoswitch, but you do not need to drain it completely. Usually, removing the fluid from the expansion tank is enough, as the radiator is below the level of the thermoswitch and will not flow back up into it. Even removing the expansion tank fluid, you should be ready for some spillage of fluid and catch and dispose of it in accordance with your local regulations. If you have not replaced or flushed your system in over two years, this is a very good time to consider performing this work as well.

Make sure the car is cool to the touch before working with the coolant.

The thermoswitch or coolant temperature switch is located just to the right of the throttle body (red arrow).
Figure 1

The thermoswitch or coolant temperature switch is located just to the right of the throttle body (red arrow). You will need to drain the coolant level to below the switch; usually, removing the coolant from the expansion tank is enough (yellow arrow). If you need additional help please see our article on coolant drain, flush and replacement.

The electrical connection (red arrow) simply pulls straight off from the top of the switch (yellow arrow).
Figure 2

The electrical connection (red arrow) simply pulls straight off from the top of the switch (yellow arrow).

Use a deep socket 19mm and remove the switch from the opening (red arrow).
Figure 3

Use a deep socket 19mm and remove the switch from the opening (red arrow).

Inspect the old switch; buildup of calcium or dirt and debris on the switch is a sign of an unhealthy cooling system.
Figure 4

Inspect the old switch; buildup of calcium or dirt and debris on the switch is a sign of an unhealthy cooling system. The switch will come with a washer (red arrow). This crush washer if installed on a clean switch and opening is enough to seal the switch. There is no need to add RTV to the switch as the previous owner did, and you do not want RTV getting into your cooling system.

Make sure to check the switch port and clean up any old corrosion or RTV to give the new switch a clean and flat mounting surface.
Figure 5

Make sure to check the switch port and clean up any old corrosion or RTV to give the new switch a clean and flat mounting surface. Installation is the reverse of removal.



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Page last updated: Tue 4/25/2017 02:48:53 AM