[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