Front Airbag Front Sensor - Captive Nut Replacement
CATEGORYBody
SECTION
8
PAGE
44
ISSUE
10/92-0259
CODE
823
Subject:
Installing/Replacing Captive Nuts
Application:
1990- 900
1989- 9000
All airbag equipped Saab 900 & 9000's use captive nuts to mount the front sensors. The following conditions would require the replacement/installation of these nuts:
^ When following the procedures outlined in the SI 01/90-1206 pertaining to surface corrosion at the Front Airbag Sensor mountings, you should also inspect the captive nuts for any signs of looseness, thread damage or corrosion between the nut insert and the body. If any of these conditions go uncorrected, it may be impossible to prevent codes Od, 10, 13 or 14 from recurring even after completing the cleaning procedures outlined in the SI.
^ The 900 inner fenders shipped from spare parts stock do not have the captive nuts installed. To insure the integrity of the SRS system, only Saab captive nuts 73 99 554 should be used. Install the nuts prior to painting the car following steps 4 through 8. Be sure to mask the top of each nut before painting.
Cars Affected:
1989- 9000
1990- 900
Parts
Action:
Caution:
Before starting any work on components related to SRS, disconnect the battery. It is also recommended that the front sensors be unplugged and moved out of the way to avoid possible damage to them or the harness when performing work in this area.
NOTE:
Do not use any chemicals in cleaning the sensor mounting surfaces or hardware. Use only clean wire brushes or taps and then blow clean with compressed air.
1. If any surface corrosion is noted on the inner fender, remove it using a clean wire brush or fine sand paper where the SRS sensor will contact the body.
2. Make certain the threads on the captive nut are clean. If necessary, use a 6 mm x 1.0 bottoming tap if available, or a small diameter (approximately 5/16") circular brush such as a valve guide brush or the brush from a firearm cleaning kit to clean the threads. Make certain that the threads of the tap or the bristles of the brush extend all the way to the tip so that the full depth of the nut is cleaned.
3. To remove existing captive nuts from the inner fenders, first remove the front SRS sensor(s). Make sure the ignition is turned off to avoid generating fault codes.
Use a drill motor with a 1/2" diameter drill bit to CAREFULLY drill through the top flange of both rivet nuts. Hold the nut to ensure there is no enlargement of the hexagonal mounting hole.
NOTE:
Drill slowly and carefully, checking your progress frequently. There is a great risk of enlarging the hexagonal mounting hole for the captive nut if you are not careful.
4. Once the nuts have been removed, clean both the paint and any corrosion from the area around both captive nut mounting points until bare, shiny metal is present in the area shown in Figure 1.
5. Place a new captive nut, P/N 73 99 454, in the mounting hole.
Thread a M6 bolt through a 1/2" O.D. washer and into the captive nut.
With the aid of an assistant, if necessary, hold the bottom of the captive nut hex body to keep it from turning. In order to allow room for the captive nut to expand ("mushroom"), hold the wrench at the bottom of the nut. It is extremely important to do so as the hexagonal mounting hole can be easily damaged if the nut rotates.
6. Using a torque wrench, tighten the M6 bolt down against the washer to a torque of 13-15 N-m (9.6 - 11. 1 ft.lbs.). This will draw the captive nut up tight against the body. See Figures 2 and 3.
7. With the bolt and washer still installed, use touchup paint to cover the small area of bare metal around the captive nut.
Remove the bolt and washer.
NOTE:
Do not get any paint on the top flange surface of the captive nut.
8. When mounting a new sensor make certain to use a light coating of dielectric grease and install the sensor using the tamper-proof screws, P/N 73 99 520.
NOTE:
New tamper-proof mounting screws, P/N 73 99 520 are required if surface corrosion that cannot be easily cleaned by wire brushing is present on existing screws.