Could a soggy air-bag go off unexpectedly?

Dear Car Talk

Dear Car Talk | Aug 01, 2009

Dear Tom and Ray:

I live here in England (my wife is from New Jersey, and she introduced me to you guys). Recently my wife and I drove our "eBay special" Renault Laguna to Twickenham in Surrey. We parked not far from the river and went for a coffee. When we returned to the car an hour later (it was a dry day), the whole street was under water. Our Renault was in about two feet of water. The car started and I backed it out whilst the locals watched me and shook their heads. After drilling holes in the foot wells, we drove home. We got the car dried out at a garage, and the engine is fine. However, the seat-belt pre-tensioners got soaked, and now the air-bag light flashes constantly. The garage could not do a diagnostic of the air-bag system on this 12-year-old banger. Do you think there is a danger of the air bag going off whilst driving? Cheers!

-- John

TOM: Quite the opposite, John. I think there's a danger that the air bag will NOT go off if you have an accident.

RAY: I'm just impressed that he happened to have an electric drill in the car, just in case he needed to put drain holes in the floor! Now, that's planning ahead!

TOM: When the air-bag light is flashing, John, that means there's a fault somewhere in the system. The car's computer runs a self-diagnosis every time you start the engine. The flashing air-bag light is telling you that the computer detected a problem, and you can't count on the system to work properly.

RAY: The seat-belt pre-tensioners are part of the air-bag system, or more correctly, the supplemental restraint system (SRS). They use small explosions to instantly cinch up the seat belts in preparation for a crash, to pull you into the correct position, where you can most benefit from the air bag.

TOM: If your mechanic is certain that the pre-tensioners are what's causing the light to flash, you can try to have them replaced. You might talk to a collision repair shop, which would have experience in rebuilding cars after accidents involving air-bag deployments.

RAY: But I'm not certain that's all that's wrong. If your mechanic was unable to scan the computer and read the codes, how does he know there aren't other problems with the SRS system? The air-bag sensor itself could have been under water, too.

TOM: So before replacing anything, I'd try to find a mechanic who can perform a proper scan for you. That may require a trip to the Renault dealer. And if you're thinking about returning to Twickenham, you might consider having the dealer install the official Renault bilge-pump and pontoons while you're there. Good luck, John.

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One