Speedraser

I've searched the forum and read lots of comments, but I'm not sure they address my exact situation, so:

After sitting too long over this very snowy winter, about a month ago I went to start my '95 993, which I've had 10 years. The battery was clearly low -- it cranked the engine -- but it started. Everything was fine, had a great drive, but the airbag light stayed on. Then, more snow. Another month or so, finally the snow (and salt) was gone, went to take a drive -- unsurprisingly, the battery was dead. Bought new battery, took the car to the shop to have the airbag light checked. No fault codes shown, reset the light, it stayed off -- then came back on two days later. Back to the shop, still no fault codes found, but now the light will not reset -- it stays on.

Any thoughts on the diagnosis before I go back to the shop to try to find the problem?

g_murray

Hi,
What 'normally' happens -- when the battery is WEAK and you try to start the car -- is that the airbag unit goes ape because it is VERY sensitive to voltage fluctuations -- especially fluctuations in the LOW VOLTAGE department.
It registers its disgust by staying ON for about 2 minutes after you start the car. (Normally the light is ON for 'ignition on' but then goes out immediately when the car is started.)
Most of us have 'put up' with this mularky by just ignoring it - some have gone to the $tealership where, for the price of an hour of labor, they 'reset' the airbag unit so that it behaves normally (i.e. airbag light goes OFF upon engine start.)
So, my friend, if your light is staying ON for about 2 minutes after engine start (but then turning off) - then that's just the airbag unit throwing a hissy fit that it's sensing (has sensed) erroneous voltages.
If it's behaving normally, i.e. turning OFF after engine start, but then -- as you're driving along happy-as-a-clam -- it's coming ON and staying ON, then that means that the airbag is NOT working - as you're driving. Obviously this is not a good thing if you ever have a crash worthy of airbag deployment.
Because it's so sensitive to voltages - it might be 'telling you' that there's something funky going on electrical-wise -- sooooo --- I would make sure that the battery (yeah I know it's a "new" one) is 'good' and that there's a good 'ground' and all your fuses etc. are 'seated' etc. etc. etc.
There IS the possibility that this is 'co-incidental' with some other part of the airbag deployment system going 'bad' (with age) i.e. the clock-spring and its notoriously weak contacts, etc. -- but my gut feeling is that it's not.
If 'all electrical' checks out and the light keeps on coming on - during a normal drive - then you may very well be a candidate for a new airbag unit.
My $.02,
Gerry

Speedraser

Thanks for the input. In my case, the light does not go out at all -- it just stays on. The first time it stayed on happened when the battery was low. After I replaced the battery, it did not show any fault code when the diagnostic computer was connected. The shop reset it and it stayed out through a couple of engine start/stop cycles. Then, about two days later it came back on (NOT happy). Again, no fault codes are shown, but now it won't reset at all. If the airbag control unit is bad, shouldn't that throw a fault code saying so?

porschemikeandnancy

I had a '95 airbag light come on. The independent shop that maintains my car told me a common occurance. He disassembled the steering wheel cleaned all the contacts - reassembled it and the light has not come on since (a year ago).

15 years is a long time for an electrical contact - which is exposed to humidity, cold, heat, etc. to not get a bit of corrosion on it.