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A/C Temperature Switch Replacement
 
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Pelican Technical Article:

A/C Temperature Switch Replacement

Steve Vernon

Time:

30 minutes30 mins

Tab:

$20 to $45

Talent:

*

Tools:

19mm wrench screwdriver, cutters

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Switch

Hot Tip:

Make sure you are replacing the right switch

Performance Gain:

Proper A/C cooling

Complementary Modification:

Recharge the A/C

The auxiliary fan on the front of your A/C condenser is used to pull more air through the condenser as the A/C heats up. The fan is controlled by a temperature switch on the receiver/dryer and should activate when the temperature reaches 126 F. This will draw more air through the coils and keep the system within its proper operating parameters. If your switch goes bad, the auxiliary cooling fan will not come on and you run the risk of damaging the system and at the very least having poor performing A/C.

The switch is located in the right front lower section of the engine bay and can be changed without removing other components. We removed the air box on our 300TD to get better pictures of the procedures, but you should be able to get your hands in there and replace it without pulling the box. If you want more room to work, please see our article on air box filter removal for further instructions.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please include your vehicle information.

The receiver/dryer is located in the lower right front of the engine bay (red arrow).
Figure 1

The receiver/dryer is located in the lower right front of the engine bay (red arrow). You should be able to change the switch out without moving anything else but if you want to pull the air filter box on the newer Turbo diesels, please see our article on how to do this.

There are two sensors or switches attached to the receiver/dryer.
Figure 2

There are two sensors or switches attached to the receiver/dryer. The one that comes off the "T" on the top is the temperature switch (yellow arrow). This is the switch you want to replace. The other switch is the pressure switch and is in the stream of the coolant; if you accidentally remove or open this switch you will vent the refrigerant into the atmosphere (which is illegal) and lose all of your coolant. Leave this switch alone!

Pull the two wire connections for the switch apart.
Figure 3

Pull the two wire connections for the switch apart.

Use a 19mm wrench and separate the temperature switch from the receiver/dryer housing (red arrow).
Figure 4

Use a 19mm wrench and separate the temperature switch from the receiver/dryer housing (red arrow).

The new switch simply screws in and there is no washer or gasket to install.
Figure 5

The new switch simply screws in and there is no washer or gasket to install. Installation is the reverse of removal.

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Page last updated: Sat 9/23/2017 03:05:27 AM