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Replacing the Bi-Level DEF Vacuum Switchover Valves
 
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Pelican Technical Article:

Replacing the Bi-Level DEF Vacuum Switchover Valves

Time:

2 hours2 hrs

Tab:

$25 to $120

Talent:

**

Tools:

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

Applicable Models:

450 SL R107 (1972-80)

Parts Required:

Bi-level DEF vacuum switchover valve

Hot Tip:

Label the vacuum lines with a masking tape

Performance Gain:

Windshield defrost or defogged

Complementary Modification:

Change out all switchover valves

If your defrost blower is not turning off then chances are your bi-level DEF switchover valve is broken. The vacuum switch-over 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.

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.

Lift the glove box out from the instrument panel.
Figure 2

Lift the glove box out from the instrument panel.

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

Once the glove box is out, you will see the vacuum switchover valves located to the right side of the cavity. They 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 crucially important.

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

Using a 8mm socket and a 20 inch extension, loosen and removed 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.
Figure 9

The bank of switchover valves are now free.

The bi-level DEF vacuum switchover valve is located on the end closest to the climate control amplifier.
Figure 10

The bi-level DEF vacuum switchover valve is located on the end closest to the climate control amplifier. 

You will notice color code circles and a number next to it.
Figure 11

You will notice color code circles and a number next to it. The color code circles are a solid black circle and a solid purple circle. You should also see the number 27 there as well. The bi-level DEF vacuum switchover valve is removed using a Philips head screwdriver. Installation is the reverse of removal.

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Page last updated: Sun 12/11/2016 03:05:09 AM