DIY: 1998 Volvo V70 Replacing Clockspring (Airbag/Horn Contact Unit)

1998 Volvo V70 PN is: 9157268.

First, thank you to all those who gave me the tips/tricks before doing this job.

This topic of Replacing Clock Spring for Airbag and Horn has been covered in different forums but not in great detail. So I will write it up in detail.
I discovered the Clockspring was broken while changing my Ignition Tumbler and Ignition Switch.

FYI: By Federal laws, any modern cars made after 1991 or so must have Airbag in the Steering Wheel. However, with the SW turning all the time, there must be a device to maintain electrical contacts to the Airbag and Horn, regardless of SW position. This is exactly what the Clockspring does, with time and mileage, the three (3) plastic legs break with the following symptoms:
- No horn (just test your horn once a month, if no horn then likely bad Clockspring).
- The SW Airbag will not function, but you will only find out the Airbag is not working after you were in a frontal collision!


OTHER USEFUL READINGS:

DIY: 1998 Volvo V70 Ignition Switch & Cylinder Lock Replacement:
http://www.matthewsvolvosite.com/for...hp?f=1&t=34472

DIY for 1999-2000 S70, S80 models:
http://www.matthewsvolvosite.com/for...ic.php?t=13514

http://volvospeed.com/Repair/ignition_S80.html

GENERAL NOTES:

- Battery must be disconnected for this procedure! But when all done, key must be in Position II before connecting battery ground cable, this is per VADIS procedure. Doing this will avoid a dash SRS light and a trip to dealer to shut it off (Hint: mucho $ at dealer to do this for you, so heed the warning!).

- You must read the attachment air bag restraint system.pdf by “jablackburn” in the thread below. Pay attention to section on page 16: STEERING WHEEL & CONTACT REEL: read this document a few times so you understand how the SRS system works:
http://www.matthewsvolvosite.com/for...hp?f=1&t=24297

- Wear Eyes Safety Goggles for your own protection.

- I call the Clockspring as “Airbag/Horn Contact Unit”.

TOOLS:
- Long Torx Set (or Long Torx Drive)
- Metric Allen Key (optional)
- 18-mm Socket
- Plastic Container for tools and nuts/bolts to avoid losing them down below the seats!



PROCEDURES:

1. Set SW straight. Copy FM, AM radio channels, then D/C battery Ground Cable (10-mm wrench).

2. Remove Upper and Lower Steering Cover (See the DIY link above for detail); basically Torx #25 bolts.

3. Remove both Turn Signal and Wiper Stalks (See the DIY link above); basically Torx #25 bolts.

4. The Airbag/Horn Contact Unit is held by two (2) Torx #30 bolts. These bolts are part of the Steering Wheel and are captive (won’t fall off when Airbag/Horn Unit is removed). NOTE the mirror showing the locations of the Torx #30 bolts.
My tip: the Long Torx Key must be at least 1-1/4” deep to reach the Torx #30 bolts. Once loosened, I used the 4mm Allen key to spin it out, although this step of using Allen key is optional.



5. Stand outside of the car and with Airbag/Horn Contact Unit pointing away from you as shown, gently pry the connector off the back of the Unit. NOTE the wiring points downward for re-assembly.
Place the Airbag/Horn Contact Unit face up in the Rear seat away from you.



6. Remove the 18-mm Bolt but do not remove the SW yet!
You need to mark the SW with Sharpie for re-installation.



7. Now pull the SW and place it in the Rear Seat.

8. NOTE the Airbag/Horn Contact Unit has 3 plastic legs, which broke after 12 years/106K miles (or may be even before it, I just did not know about it!). Also note the 2 prongs that fit into the SW slots.

 

cont'd from above...

9. When installing new Airbag/Horn Contact Unit, note: Green and Black Connectors as shown.
The Black Tab is for cancelling Turn Signal.



10. Now install the Airbag/Horn Contact Unit, loosely tighten the Torx bolts as in the sequence 1-2-3. Then tighten #1 finger-tight, followed by #2 and #3. Doing so will prevent stress to the unit (let’s say you tighten #2 and #3 first, then when you tighten #1, you put stress in the #1 plastic tab!).
- NOTE: behind the SW is the “Ground” Brush to maintain ground contact to the Airbag/Horn Contact Unit all the time regardless of SW position.
- Apply small amount of grease on the metal ring of the Airbag/Horn Contact Unit.



11. This step is important: The Airbag/Horn Contact Unit can turn about a total of 5.5 turns (each turn = 360 degrees). So the Black tab needs to be in the middle of the 5.5 range. Spin the reel CW (Clockwise) and CCW and you will see how it works. This is how it functions when you turn the SW Right and Left.
- Per Volvo procedure, remove the lock screw on the new Airbag/Horn Contact Unit, turn the black tab all the way CW first until it stops. See Yellow Circle.
- Now turn the black tab CCW approx. 2.75 turns as shown (Red Circles #1-2-3), then temporarily pin it in place with the lock screw so it does not move during SW installation.



12. Now install the SW making sure it lines up with the Sharpie marks. Then finger-tight the 18-mm bolt so the SW does not slip off.
- Note the 2 plastic prongs fit into the SW slots. These 2 prongs drive the reel of the Airbag/Horn Contact Unit .
- Now remove the lock screw. This step is crucial, failure to do this step WILL damage the Airbag/Horn Contact Unit when you turn the SW! Place the lock screw with the yellow label as shown (this is factory position).
- Now tighten the 18-mm Bolt. I don’t know the torque but tighten it until it stops, then give it a firm tug while using your knees to keep the SW still. The bolt has Loctite and will stay in place anyway.



13. Re-install Airbag/Horn Contact Unit, but first making sure the green connector’s wiring pointing downward as shown in Step #5 above. The green connector has 2 pins, 1 pin is for the Airbag and the other pin is for the Horn I think.
Tighten the two (2) Torx #30 bolts finger-tight.

14. Before you get too excited and connect the battery, STOP!
- Insert the key and turn the Ignition to Position II. Don’t ask me why but Volvo says so.
This allows the SRS system to do a self-check when the battery cable is re-connected to avoid a SRS dash light (if the SRS light is on, this means shelling out money for the Volvo dealer to reset the SRS light for you).
- Now re-connect battery cable.
- Start the engine and drive around the block to check.
That is all boys and girls, not difficult if you follow the above steps religiously! Then call you mom and tell her you just did something good today, and she will say “Good Boy!”; now you can drink your favorite beers…..

 

Autopsy of the Airbag/Horn Contact Unit:

1. Note the "Ground Tab", which maintains Ground connection regardless of SW position.

2. The Reel has 2 wires in it, so it is clear that 1 wire is for Airbag, and the other wire is for Horn.
Interesting that the Larger Green connector (rectangular) can only be connected one way, but the Smaller Green connector that goes to SW (with 2 pins) seems to be reversible and can be connected wrong if one is not careful about it!

Considering that this device performs 2 important jobs:
- Horn (this could be life-and-death) and...
- Airbag
I'd not consider fixing this at all. It is a crucial device that you only find out whether it works or not until it is too late!
So if your horn does not work, investigate further!

 

Well since you didn't respond to my PM on 12-5-2010 to please correct this post i feel compelled to respond here...

...while your post here has lots of good detail on how to replace the SRS clock spring, there's some serious mis-info there too.

The clock spring has two conductors; both are for the air bag; pwr and return. Neither is for the horn!! The horn connection is made through slip ring that you said is for the ground connection.

Also how was your clockspring broken? If either of the conductors were broken, you should have seen a SRS fault lite on your instr cluster!! The SRS system does a POST (pwr on self test) upon every key-on. And again the horn circuit is completely separate and unrelated to the SRS circuitry!!

Regards,
greg

 

Thanks for the info! I learned something new!

The clockspring was broken at the 3 plastic mounting prongs. So the ground contact was lost ---> NO horn, however according to your note, then the airbag circuit was still OK even with lost ground circuit on the clockspring.

Thanks again for the info!

 

gdog,

Just curious, do you know how the horn circuit is completed when you hit the horn?
The ground is via the brush mounted behind the SW, so when you hit the horn, you complete the ground circuit?