[Fixed] Air bag problem - light on constantly but dim
So, I reconnected my battery tonight. Started the car and let it idle while I tightened down the battery. I then started to hear beeping from inside the car. Shut the car off and restarted it. I didn't pay attention to number of beeps or pattern but the beeping coincided with the airbag light flashing.
On the second start the air bag light came on for the usual six seconds, went off and then started flickering. Not flashing, flickering. I took it out for a drive and the light was on and off. Not flashing but on dimly and flickering. Sometime almost imperceivable in daylight that it was even on.
Now it seems to have settled. The light comes on for six seconds at normal brightness and then goes to a dimmer state and stays on constant.
I have read that the beeping is not a trouble code but is communicating a need for service and is used when the air bag light is not functioning. Also, constant on means the diagnostic monitor is not connected or not functioning. I'll check its connection tomorrow but wonder if there any ideas on what this might be. I haven't read elsewhere about the light being dimmer that usual and/or flickering.
On the second start the air bag light came on for the usual six seconds, went off and then started flickering. Not flashing, flickering. I took it out for a drive and the light was on and off. Not flashing but on dimly and flickering. Sometime almost imperceivable in daylight that it was even on.
Now it seems to have settled. The light comes on for six seconds at normal brightness and then goes to a dimmer state and stays on constant.
I have read that the beeping is not a trouble code but is communicating a need for service and is used when the air bag light is not functioning. Also, constant on means the diagnostic monitor is not connected or not functioning. I'll check its connection tomorrow but wonder if there any ideas on what this might be. I haven't read elsewhere about the light being dimmer that usual and/or flickering.
Comments
Having the cables sitting loose on the battery terminals could mean there was a surge of alternator current/voltage in the car's electrical system IF the battery connection had any slight interruption in its connection to the rest of the car. This is something that cars from the 60s and 70s could handle (letting a car run off of the alternator while you swap batteries or remove or install battery connections) but cars with electonic components in them require a little more sensitivity to how you do things to them. Although you may have been able to do this time and time again in the past without any problems I DO NOT recommend doing anything on these cars while they are running with loose battery cables.
As with any ELECTRONIC item a glitch in the device's processes can cause problems that a cold start can cure.
This still goes against the argument for proper procedure after a battery reconnect, but I may have just turned the ignition to ON and not started the car before the battery cables were tightened. The car has an aftermarket alarm and, as soon the battery is reconnected, the alarm sounds. My reaction is to silence the alarm and I guess I just need to tough it out for the extra minute or so it takes to get things done right.
Yesterday, I did not start the car but turned the ignition to the ON position and the air bag light was back to behaving as normal. I do want to reset, disconnect everything and try again. I'm suspicious of this fault now and have read these problems can come and go.
It was a royal pain to replace the clock spring (twice). I never had removed a steering wheel before and I was nervous about detonating the air bag. The 1993 service manual states that the air bag backup power supply must be disconnected. However, this does not seem to exist on the 1993. It does exist behind the glove box on my 1991. From my research, I think in 1993, the diagnostic module serves the purpose of backup power supply and one minute of no power is enough to discharge the capacitor that serves this purpose. Regardless, I waited for a full 15 minutes of no power before disconnecting the air bag.
So, having failed with the clock spring and subsequently flashing a code "35", I replaced the airbag diagnostic module. It was available through my local Ford dealer. Though, it was on back order and I didn't get it until last week. The part # is F2AZ14B056A and it was $235. This was not an NOS part. The sticker on the module had an August 2013 date. That's probably a good thing because I wouldn't want to 20 year old electronic part if I could help it.
With it installed, no more flickering air bag light!
If you have to replace this, I followed the 1993 service manual for removal. It didn't say to, but, I did remove the climate controls, though, not totally disconnecting them, just enough to expose the module which is directly behind them. There are two wires connected to the module and they were most easily removed from the drivers side foot well reaching in blindly and unplugging. There is not enough space to get leverage on the connectors from the stereo/climate control opening.
The manual says four screws but shows two screws on the bracket. There are, in fact, two screws. The manual doesn't tell you but there are three other wires that are secured to this bracket via plastic clips. Once the bracket and attached module are free from wires it can be removed through the passengers side foot well. I did not remove the glove box but it took a lot of maneuvering. So much so, that I though there must be a better way to replace it.
To replace, I put that bracket alone through the opening I removed it from and then put the new module in after it keeping both oriented in the correct way. I then snapped the module into the bracket after both were behind the dashboard. Reassembly was straightforward from there.
My YB flashed an air bag 3-2 (if I remember correctly) the other morning on my way to work but it eventually stopped. To deter rodents from the wooded surrounding lots from getting under the hoods of all of my cars I keep the hoods propped slightly and believe the code could have been rain/moisture related that dried out with the drive but am keeping an eye on it.