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Entire Bank of Vacuum Switchover Valves Replacement
 
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Pelican Technical Article:

Entire Bank of Vacuum Switchover Valves Replacement

Mike Holloway

Time:

2 hours2 hrs

Tab:

$120

Talent:

**

Tools:

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

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

Entire bank of vacuum switchover valves

Hot Tip:

Label the vacuum lines with masking tape

Performance Gain:

Windshield defrost or defogged

Complementary Modification:

Upgrade amplifier

The vacuum switchover valves on earlier models control several functions, including the locking system as well as the climate control. If you notice that your idle speed is coming down by a few hundred rpms during warm-up yet it's baseline is up to 1,650 rpms instead of around 800 rpms, this may indicate that the vacuum-switchover valves may need to be replaced. Please note, the vacuum switchover valve is active when air conditioning is on and this will tend to increase your rpms. In order to get at the switchover valves, the glove box must be removed.

In other projects involving specific vacuum switchover valves, we showed you how to identify and replace specific vacuum switchover valves that controlled specific functions in your 450SL's interior. In this project, I will show you how to replace the entire bank of switchover valves.

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.

Carefully lift the glove box out from the dashboard.
Figure 2

Carefully lift the glove box out from the dashboard.

Once the glove box is out, you will see the vacuum switchover valves located to the right side of the hole in your dash where your glove box normally resides.
Figure 3

Once the glove box is out, you will see the vacuum switchover valves located to the right side of the hole in your dash where your glove box normally resides. The vacuum switchover lines are color coded with representative lines. You can start by pulling out the electrical jack located at the front.

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. This can be removed 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 with masking tape and indicating which line feeds which switch is very important. You want to make sure that you correctly attach the appropriate line to the corresponding switchover valve. You will notice that each switchover valve is color coded with its corresponding line. Make a note or chart of which line corresponds with which valve to make sure that you install the new bank of switchover valves correctly.

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

Pull off each jack which 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, locate the lines connecting the switchover valves and clip the cable tie.
Figure 8

Using wire-cutters, locate the lines connecting the switchover valves and clip the cable tie. The cable bundle will be located towards the driver side.

The bank of switchover valves are now free and ready to be replaced.
Figure 9

The bank of switchover valves are now free and ready to be replaced.

Using a Phillips head screwdriver, the switchover valves can be loosened and replaced.
Figure 10

Using a Phillips head screwdriver, the switchover valves can be loosened and replaced. Installation is the reverse of removal. Be sure to correctly mate the lines with the corresponding switchover valves.

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Comments and Suggestions:
Louis Comments: Thanks for the info. However my vehicle is a 1984 500sl. I bought the vehicle as is,but it seems that the car was worked on before and not very successful. The car was also resprayed. Present problems seem to be little or no vacuum on the engine. Do you have any advice on how to proceed?
Regards
Louis
September 13, 2016
  Followup from the Pelican Staff: if no vacuum, check mechanical engine timing. It is likely faulty. - Nick at Pelican Parts  
Louis Comments: I have a 1984 500sl vin no wdb10704622001037. I am having trouble to get the vacuum system working. Could you please advise me on pipe layout and colours. There is hardly any suction on the engine side and some of the valve do not seem to function. Could you please help
September 9, 2016
  Followup from the Pelican Staff: There should be a vacuum diagram on the underside of the hood.





- Nick at Pelican Parts
 

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