Hi everyone,

Once in a while the horn would quit when the wheel was turned 90 degrees,
and then begin working normally when driving straight.
Now it quit.

I couldn't find Volvo info or a good tutorial for the 940 with the steering wheel air bag.
There's no info in the Haynes service manual

The FAQ covers the 740 and mentions disconnecting the battery to safely disable SRS. Is a ten minute wait OK to start removing the steering wheel?
Is there a Volvo service bulletin for this?

Details like removing the plastic horn buttons are fuzzy, and now there's no
junk yard university and plentiful spare parts if something breaks.
I'd like to know more before I start the job.

Do the spring loaded horn contacts and slip ring just need dressing or wear out?
Are the slip ring and contacts asked to carry too much current?
Adding a horn relay is no big deal, how many people opt for that?

What specific parts should be replaced?

Thanks, Bill

[Bill, here’s now my best attempt at a response]

The horn contact ring in the steering wheel is part of the clockspring assembly mounted at the top of the steering column with a spring loaded, metal tipped contact button imbedded in the steering wheel. Access to the horn ring and clockspring will require disabling the SRS system and removal of the steering wheel.

I had submitted a complete feature article for the FAQ here on the clockspring some years ago, including pictures, but I can no longer find it. It may have been removed during the last major edit done some years ago. I will include excerpts here.

STANDARD DISCLAIMER: Any work involving the SRS system is done entirely at your own risk. The brickboard and its contributors assume no liability, including failing to provide accurate or complete information or you not being able to follow instructions. Seek the services of a qualified technician if you do not understand or are not confident working around SRS components.

Disable the SRS system by disconnecting the battery negative terminal and safely bagging it out of the way. A two minute discharge is considered adequate.

Start by peeling back the airbag cover for access, starting across the top -don't stretch it any more than you have to, doing it in warmer shop conditions is a good idea. Remove and disconnect the airbag (two torx screws and connector). When disconnecting the airbag wires or handling them, avoid touching the bare contacts and avoid any stray electricity or static discharge.

Removal of the steering wheel of course requires removal of the steering column nut. You will need a breaker bar and short extension. You will likely not be able to restrain the steering wheel by hand. Tie a rope through the crossbar and around the upper door frame, slamming the door shut on the rope before tightening the rope knot. Leave the window fully open for access. You should now be able to loosen and remove the lock nut.

BTW, if the horn button switches need to removed, there are tips in the FAQ. Much of the rest of the information there is for pre-airbag days.

Prior to removal of the steering wheel, you need to secure the clockspring from unwinding. You do this by advancing the lock screw in between the plastic locking tabs. During steering wheel removal, do not turn the steering wheel which will risk breaking the plastic lock tabs. Note the precise orientation on the steering column splines with a felt pen and scribe before you begin. For re-installation, best to use a torque wrench, again using the rope, 44 ft-lbs is the spec I see in an aftermarket manual. Do not forget to back off the lock screw when you are done.

Although a puller is often suggested for use with steering wheels, you shouldn’t need to do this. Pound firmly with your fists behind the steering rim at the cross yoke. Pound both together and alternating. Within about six good pounds it should start to loosen and can be wiggled off the splines.

You will now have access to the horn contact ring and the horn contact button. If you're lucky, the contact ring and/or button contact may just need a good cleaning. A wipe of dielectric silicone grease can be used as a lubricant and as I recall is recommended, but can also attract dust and dirt. If the button is worn out or one of the wires is broken that connect to the horn button switches then the part is still available as p/n 1387738 from Volvo and through resellers like ipd https://www.ipdusa.com/products/22469/Horn-Slip-Contact-740-760-780-940-Genuine-Volvo-1387738-140699

Failing that, there may be a problem with the horn ring being worn out or the wiring to the clockspring somehow having failed or the clockspring itself having cracked or been damaged. You will then want to remove the clockspring to use a meter to verify continuity. Just make sure the locking screw remains in place, otherwise the clockspring may unwind and will now need centering (please re-post if this happens for further advice). If not centred correctly and the alignment with the steering column preserved then the clockspring may soon break from strain when reaching end of travel at the steering end locks. With the clockspring not in place, you must not turn and loose track of the steering column or wheel position such as to lose rotational alignment when the clockspring was removed. BTW, if this happens and the clockspring breaks, as once happened with me when an idiot body shop tech put a steering wheel back on incorrectly, best to seek a used clockspring from a low mileage wreck rather than new as they ain’t cheap.

Good luck.

As a tip here while I’m mentioning this. Some 900s develop an annoying squeak at the top of the steering column. If you ever remove the clockspring, you could take that opportunity to grease it. It's a bit fussy to do, as follows. There’s a tapered white plastic spacer ring on the steering shaft visible behind the clockspring. It’s held in place by a circlip sitting in a slot. Note that the spacer ring is supposed to have a split in it -so don’t get excited. The spacer ring sits at the top of the steering shaft upper bearing. There’s a corresponding steel metal spacer ring that you can’t see on the under side of the upper bearing. You can push a little grease around the spacer ring if you want, just don’t remove that circlip or remove the plastic spacer unless you’re prepared for an adventure –they can be difficult to get back on and may necessitate removal of the entire upper steering column. I'll mention here for others who may read this, on some 700’s (not 900s) the metal spacer may be on top and the plastic one on the bottom. In those cars, if the steering column has developed a clicking sound then upgrading to the new style of spacers is one possible cure, but both rings must be replaced and the upper steering column will need to be removed (non-trivial). There’s a technical bulletin (TP 30801 dated Jun-89) fully describing this upgrade.

Again, good luck.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Bill, in reply to your earlier response in this thread and in your email, and as follow-up to my above reply:

The YouTube link you gave now comes up as video deleted -this occasionally seems to happen for reasons I don't understand. A search turned up the same or a similar video of 940 steering wheel replacement. Although extremely similar, it doesn't entirely match my old notes or my vague recollections of doing the job almost 10 years ago. I'm wondering if things changed slightly by the final year '95 I have or if the 940 in the video was not North American or if it's my memory (could well be the latter). I see in my old notes that '93+ OBD for SRS is different from pre-'93, so that indicates a change and may well explain minor differences. Although the narrator says to wait 30 mins to discharge, Volvo states 2 minutes is adequate. The SRS system is designed to maintain voltage for only a few moments after a crash, not minutes, which could actually be hazardous if there was a delayed deployment, and the capacitors will be spec'd to hold a charge accordingly.

The video also uses the steering column lock as the restraint while removing the steering wheel bolt -I quite remember this was advised against. When I removed the steering wheel, it took a lot more force than in the video. Pulling the steering wheel was also much more difficult than in the video. I assume he had everything apart once prior to recording. All my original notes were based on Volvo documentation and my need to check and replace a broken clockspring related to the SRS light, not the horn function. I had online access to the Volvo SRS manual and TSBs at the time, but can no longer seem to find them (possibly on an old .RU site that no longer exists).

I neglected to include from my old FAQ notes that the Torx screws (T30) for the air bag are accessed from behind the wheel with the steering wheel at an angle, as in the video. I always remove the steering column covers, providing access to electrical connectors, but the video indicates this isn't necessary for simply steering wheel removal.

You asked about horn button switch removal. I have not had to do this. The FAQ mentions gently prying the switch cap up. If you look at the switch in parts diagrams, there are 4 small tabs extending from and holding the button cap, 2 on the top edge, 2 on the bottom edge, maybe about 1/4" in from the sides. Using a thin blade to gently push in the two tabs on one edge while you also pinching the cap should allow you to pry up that edge a bit, then do the other edge.

You indicated the horn worked at various steering wheel angles until it finally no longer worked. You didn't mention if only one horn button initially stopped working and it's now both, or if both failed at the same time. If both failed together then the problem is likely at the contact button or in the clockspring. My guess is the contact button. To replace the contact button (p/n noted in above reply), you will likely need to remove both horn button switches to connect the two long wires. Another option would be not to remove the horn buttons and splice the visible wires instead, but my preference would be to do it properly.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

[Bill, I'll keep my responses going here for the benefit of others who may be following this horn problem thread or may later find it.]

You mentioned in your email that you've now determined the steering wheel horn button switches and spring loaded contact button check out okay. As you suspect, the problem is now likely in the clockspring. Before replacing it, you'll want to do some further testing to verify this, checking for zero or minimal resistance throughout the range of rotation.

Time to pull the clockspring and take it to the bench. First, make sure the front wheels are pointing straight, remount the steering wheel as needed, being sure to back off the lockscrew so as not to break the tab. You can now remove the clockspring to the work bench. It's simplest to keep the lock screw in place, but it's no longer critical. You're going to re-centre the clockspring to the neutral position before re-installation. The clocksprings are not at all repairable. If nothing is broken or worn out then you may be able to get some spray contact cleaner inside to get it working properly. I just tried to find my old broken one to see how you well you might be able to accomplish such things. I saw it somewhere in the past year, but I think I may have finally thrown it out.

To set the clockspring in the neutral position prior to installation, let the clockspring unwind to the fully relaxed position. Now count the turns until it's almost tight (don't at all force it, especially a well used one). This will typically be about 6-1/2 turns. Now split the diff and position it at the mid-point, let's say 3-1/4 turns. Now back it off to align the locking tab and lock it as now being in the neutral position. If you're so close to aligning the tab that you want to tighten he spring a bit, I would never go much more than about 1/8 turn. Much more than that and you risk straining and ultimately breaking a tight spring when the wheels are hard to the right. [An apprentice of questionable training at a body shop once had to replace the steering wheel air bag in my wife's 940, but did not know to centre it. The first time it was parallel parked, the SRS light came on, no airbag circuit, a broken clockspring, hence why I know all this stuff. I would no longer let that shop touch the car (they'd made other mistakes) and made them buy me a new one.]

There are two similar looking clocksprings used in 940s, an early style (p/n 9140587) up to '93 and a later style (p/n 9434427) for '94-'95. Verify your part number before seeking a replacement. Both are discontinued and NLA from Volvo. You may find the odd one on eBay, almost all are used. As you won't know how used, my preference would be used from a known lower mileage one in a yard. Note these both have other Volvo fitments if you're looking for a used one).

Good luck and post back with your final fix.

[You also asked if the car would run without the clockspring. Yes, it will run, but the SRS light will be on and the entire SRS system will likely be disabled, plus no horn. I would never, ever recommend or want to drive like that. You also asked about taking an accidental airbag deployment in the face. You can easily suffer bruising, abrasions, broken and hopefully not shattered eyeglasses and perhaps a bloody nose. A lot depends on the angle and how close and centred you are to the airbag or being hit by the cover. My wife got all but the bloody nose when her 940 was once rear ended at street speed while stopped in line and waiting for the light to change. Airbags are designed not to go off in a rear ender, which initially confused the police report suggesting the van ahead was backing up at the same time she was hit, initially putting some of the blame on the van driver. Turns out she was pushed into the wheelchair lift of the van ahead then ricocheted back to be sensed as a frontal impact by the SRS module and consequent deployment. Took her a few weeks to recover from that and relatively minor whiplash. Getting the 940 back from the insurance company and finally fixed is a longer and more complicated story.]
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Thanks for the detailed reply.

My 945T is a 93 and I suspect the clockspring is open.
Tomorrow AM I'll try to measure continuity in place between the two connectors
which should verify it's busted.

There's one wire to the horn buttons from the clockspring and brush,
apparently the return ground for the horn switch is through the steering column. Is that right? It's unclear to me how that 2nd leg is connected.
The wire goes to the central casting of the steering wheel, but how is the casting grounded? Is the steering linkage a reliable ground?

I've found that the clockspring p/n is 9140587 (old nr 3516420)
Tomorrow I'll check a few local places to see if they have it or order online.

There's a Volvo TSB for clockspring recall for some AWD models that should have been handled by the dealers.

That's scary what happened to your wife with the airbag punching her in the face.
There's a good reason to avoid hard plastic coffee mugs while driving.
I wonder what happens when the air bag deploys when you're swigging coffee from a hard plastic cup?
Wearing eye glasses is another problem area.
I wonder how many people are injured or killed by air bags?

Where is the 900 series clockspring install data from Volvo? Could it be in a TSB?
There's a nice AWD clockspring write-up here that should be similar:
https://www.matthewsvolvosite.com/v70-clockspring/

Cheers, Bill

Volvo SRS green manual Section 8(88) for your 1993 940 is variously listed as TP32181 (940/960 SRS preliminary 1993), TP32231 (SRS Airbag 940/960 1993-on) and TP32224 (SRS Airbag 940/960 1993-on, UK???). At this moment, a Google search may turn up partial copies for preview. It's not overly complicated as long as you have a basic understanding and know how to play safe with SRS components. A proper electrical wiring diagram plus tips that can be found online such as here should suffice. The TSB I was thinking of (Technical Service Bulletin sent to dealer service) may well have been the one you mentioned for the later AWD.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Bill,
My initial response needs extensive editing that I don't have time to complete at the moment. Please ignore the contents of the email notification as it is incomplete and misleading. I will repost here as as soon as I can. Best not to attack the steering wheel until you know more. The horn ring is part of the clockspring. It is a very tricky area to work in and you can easily break things.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd hav

Hi Dave,

I found a YT video of someone changing a 940 steering wheel that was pretty good:
www.youtube.com/watch?v=S4TIcdv4sPk

He waits 30 minutes after unhooking the battery neg cable to start work.
(Volvo says ten minutes on the 850)
He showed how easy it is to remove the air bag.
He showed the clockspring and how to secure when removing the wheel.
Also he explained how to install a new clock spring.

What I didn't see highlighted were the contacts that break and kill the horn.
What"s the trick to get at the horn buttons without breaking the plastic cover.
He was mumbling when he gave the torque specs for the wheel lock bolt.

Do you think a horn relay is a good idea? It should be easy to mount near the RSR and pick up the +12V there.

Thanks, Bill