Aux Fan Switch
Drier-wpreswitch-web

Aux Fan Switch

$34.95

A more responsive, pressure-operated aux fan switch that mounts on the receiver drier.

  • Upgrade for the W123 aux fan switch
  • Original equipment on the W124 and W201 (replaces 004 820 68 10) and some W126 and R107 models
  • Fan on at 220 psi, off at 149 psi
  • 3/8″-24 thread; HNBR o-ring included
  • Plugs into the original terminals
SKU: SWREDAUX01 Categories: , , , , , ,

Overview. The stock W123 aux fan switch is slow to respond, leading to big temperature swings at the vents. This red pressure-operated switch turns the aux fan on based on system pressure for better A/C at idle.

Specifications

  • Switches aux fan on: 220 psi
  • Switches aux fan off: 149 psi
  • Thread: 3/8″-24 male, with HNBR o-ring

Fitment

  • W123 (upgrade)
  • Some W126 and R107 (OE replacement)
  • W124, including 1990 300E (OE replacement for 004 820 68 10)
  • W201 190 / 190E / 190D (OE replacement for 004 820 68 10)

Cross-reference part numbers (this switch replaces):

  • Mercedes-Benz A 004 820 68 10, A0048206810, 0048206810, 004 820 68 10, 004 820 6810, 004-820-68-10, 004.820.68.10

What’s included

  • Red aux fan pressure switch
  • HNBR o-ring

Installation

On a W123, remove the secondary hex plug on the top block of the receiver drier and install the switch there. The electrical pigtail has terminals that plug straight into the original terminals.

Product FAQs

Will it fit my drier?

Yes if the drier has at least two 3/8"-24 ports, like our W123 Receiver Driers. See the image in the product gallery. This switch is installed in the top block of the drier.

How is this different from the original W123 aux fan switch?

This part is used on later Mercedes, and uses system pressure as an operating principle instead of temperature. Pressure response is more immediate, shortening the switching interval for the aux fan to turn on and off. This leads to less temperature variation at the vents, and less load on the electrical system overall as the fan shuts off sooner when the car is off the line and pressure drops. Unlike the original W123 aux fan switch, it is necessary to evacuate the a/c system to install this switch, so we recommend upgrading it in conjunction with major service.

I upgraded to this switch and it worked for a while but recently stopped working. The a/c is still pretty cold. Is the switch bad?

We call this switch "the spring tell-tale" because when the system is losing refrigerant slowly, the first indication is often that this switch stops closing. We often hear from customers that take their cars out of storage in the spring having this issue. The good news is, this is a superior grade switch that will work as intended once the system is recharged to proper pressures.

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