Spiral cable failure

  • 2010 TOYOTA
  • 182,400 MILES
What can happen if you are driving a car with a faulty spiral cable and defective airbags. I ask because I lost control of my car and had an accident and I need to know if the spiral cable could have been the cause.
Do you
have the same problem?
Wednesday, August 9th, 2017 AT 1:07 AM

1 Reply

I assume you are referring to the wound-up ribbon cable inside the clock spring assembly. Those typically break on one end, then the air bag computer will detect the open circuit to the steering wheel air bag, set a diagnostic fault code, then turn on the red warning light. In some cases the ribbon cable becomes shredded and torn apart. The biggest concern I have with that is sometimes the copper wires will peek out from under the steering wheel and be exposed. I do not know how that can happen because everything is inside a plastic housing, but I saw it for myself on a customer's car many years ago. Sliding across the seat can generate static electricity, then if you touch the right wire, you could pop the air bag. When you walk across a carpeted floor, then get a shock on a door knob, that is at least 3,000 volts. For demonstration purposes, an air bag can be deployed with a nine-volt transistor battery. That shows that static electricity can easily set off an air bag.

The good news is conditions have to be just right for static electricity to pop the air bag. When the ribbon cable is that badly unraveled, the two wires involved are typically shorted together. Any static charge applied would be applied to both wires equally, so the difference between them is 0 volts.

I have never heard of a clock spring being so bound up that the steering wheel could not be turned. For that to occur, the ribbon cable would have to have been broken for a long time. If this came up in a lawsuit, the driver would have to explain why he was driving the vehicle with an obviously malfunctioning safety system. The ribbon cable would have to have been broken, and the warning light would have been on for quite a while. Even then, there is not much to the ribbon cable. The additional effort to turn the steering wheel would barely be noticeable.

When a clock spring is not centered properly, the ribbon cable will either unwind fully, then fold over on itself when turning one way, or it will wind up fully when turning the other way, then tear off on the end. The resistance just before it tears off is almost impossible to feel because it is so slight compared to the effort needed to turn the steering system. There just is not enough there to cause hard steering.

If the steering system suddenly became hard to turn, the better suspects are a tight universal joint in the steering shaft under the dash, leakage in the rack and pinion's spool valve, a weak power steering pump, and less commonly, a tight lower ball joint.
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Wednesday, August 9th, 2017 AT 3:45 AM

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