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Pelican Technical Article:

Main Vacuum Switch Replacement

Mike Holloway

Time:

2 hours2 hrs

Tab:

$25 to $120

Talent:

**

Tools:

Flathead screwdriver, 8mm socket, 20-inch extension, wire-cutters, trim removal tools

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

Vacuum switchover valves

Hot Tip:

Label the vacuum lines with masking tape

Performance Gain:

Comfortable cabin air

Complementary Modification:

Change all vacuum switches

If your fan doesn't work when switched to low or high, there is a good chance that the main vacuum switch is at fault. In order to get at the switchover valves, the glove box must be removed. In this project, I will show how the glove box is removed. Then, I will go through the steps involved in replacing the main vacuum switch that controls your fan.

Before you do any work on your car it is important that you wear safety glasses, work gloves and dispose of all fluids in a safe manner. Coolant is poisonous and should be treated as such. Animals and small children have been known to die from ingesting coolant. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. Always wear eye and hand protection. Disconnect the battery before working on your car.

Using a flathead screwdriver, pry off the plastic fastener that holds the glove box in place.
Figure 1

Using a flathead screwdriver, pry off the plastic fastener that holds the glove box in place. Be careful not to break the inset or the fastener. There will be two fasteners to remove that hold the glove box in place.

Carefully lift the glove box out from the instrument panel.
Figure 2

Carefully lift the glove box out from the instrument panel. Since it is rather delicate, you don't want to damage the glove box while you're removing it from its home in the dashboard.

Once the glove box is out, you will see the vacuum switchover valves located to the right side of the car.
Figure 3

Once the glove box is out, you will see the vacuum switchover valves located to the right side of the car. The vacuum switchover valves are all color-coded with representative lines. You can start by pulling out the electrical jack located at the front of the switchover valves.

Next, notice the terminal jack, which sends signals for all the valves.
Figure 4

Next, notice the terminal jack, which sends signals for all the valves. Remove the terminal jack by slipping the metal clasp downwards and pulling the jack straight out.

The vacuum lines can now be removed.
Figure 5

The vacuum lines can now be removed. The yellow check valves are an easy starting point. Labeling each check valve with masking tape and indicating which line feeds which switch is very important. Remember that you're supposed to be fixing your car, not making it worse. Take your time and do a thorough job.

Pull off each jack that is connected to each switchover valve.
Figure 6

Pull off each jack that is connected to each switchover valve.

Using an 8mm socket and a 20-inch extension, loosen and remove the three bolts holding the switchover valve plate.
Figure 7

Using an 8mm socket and a 20-inch extension, loosen and remove the three bolts holding the switchover valve plate.

Using wire cutters, clip the cable tie that holds them together after locating the lines connecting the switchover valves.
Figure 8

Using wire cutters, clip the cable tie that holds them together after locating the lines connecting the switchover valves. The cable bundle will be located towards the driver side.

The bank of switchover valves are now free.
Figure 9

The bank of switchover valves are now free.

The main vacuum switch has a color code circle next to it and a number.
Figure 10

The main vacuum switch has a color code circle next to it and a number. The color code for the main vacuum switch is a green circle with a red stripe running down the center and the number 14. 

The vacuum switch can be removed with a flathead screwdriver.
Figure 11

The vacuum switch can be removed with a flathead screwdriver. Installation is the reverse of removal.

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Page last updated: Mon 12/5/2016 02:42:49 AM