air bag light constant (no flashing)

[davetheshrew]

Hi

Ive seen quite a few posts about airbag light flashing, mine doesnt do that. Its constantly on. When i turn the key to start it disappears briefly and then just stays on. I removed the clock spring and tested each pin for continuity, no problem with the clockspring, all wiring looks good. Anyone else had this problem? Is there a fuse im missing somewhere or something? 1997 diesel bongo btw. Thanks

[powsurfer]

Did you manage to sort it?
Mine has today just started doing the same. Goes off briefly after starting but comes straight back on and stays on. Doesn't flash.
I did have it flashing about 6 times a while back but not every time I drove. It did that for a couple of months but then no problems until now.
I've recently had the centre console and alternator out to change fan and air con belts. I also had to replace the main 100amp fuse that I blew a couple of times.

Does anyone know what could be causing this or have a fix?

[g8dhe]

The usual cause of the 100 Amp fuse blowing is a problem with the alternator or its cable to the 100 Amp fuse. Its possible (on a V6) for the oil from a leaking cam shaft seal to run down and into the alternator causing it to overheat and eventually blow the 100 Amp fuse as the diode pack in the alternator fails.

[powsurfer]

Yes Geoff, this was a schoolboy error of mine... missed putting the insulating washer back on when putting the alternator back.
I was wondering if this could have had an effect on the air bag light issue?

[g8dhe]

No no obvious direct connection, possibly if the battery was low in charge and hence voltage it might cause it to come on but I don't think I've heard that reported before.

[powsurfer]

Ok, thanks Geoff. I've got a few things to try. I'll report back if I manage to solve it

[powsurfer]

I've managed to turn off the air bag warning light, but not sure why this would happen?

I connected the relevant pins in the diagnostic box - D +B Switched battery voltage to T FAB Trouble code output (air-bag diagnostic monitor computer)
Then when I started up expecting some fault codes I got nothing but the air bag light has stopped coming on/staying on.

Could this just have caused a reset or do I need to keep looking for the actual fault that may have been causing it?

[g8dhe]

Are you sure about your connections ? FAB is the Output and you connect a lamp to that the other side of the lamp connects to the +12v

[powsurfer]

Yes I've just checked, I didn't use a lamp (was going to look for flashes on dash), just a direct cable between those two.
Is that not correct, pretty sure it is how I did it many years ago from PhilMcfadden's instructions.

Could that have just reset the fault?
(fault possibly triggered when blowing the fuse/having batteries disconnected)

[g8dhe]

The outputs for all the other error reports is for a Lamp connection. There isn't an Input for the Air Bag listed on the http://www.philmcfadden.co.uk/MazdaDiagnosticBox.htm site

The other ECU outputs you earth the input lead and then watch the corresponding lamp on the output, later versions Flash the Hold light etc.

[powsurfer]

Ok thanks geoff.
Am I likely to have done harm then as it seems to have solved the issue I had?
I only remembered from years ago using it this way to get the hold light on the dash flashing the error codes.

[g8dhe]

There isn't a circuit diagram for the ECU or Air Bag computers so can't be certain, but its quite possible that it might have damaged the transistor that drives that pin as they merely earth that line so a full short may well have done damage but I can't be certain.

[powsurfer]

Thanks Geoff, I guess that either means it is not reporting it or it is not working then.