I have a 1984 626 super deluxe (australian model) and have a ****ling issue to do with the warning chimes.

I have noticed I have three different chimes:

1 - a four tone chime when the lights are left on with engine off
2 - a long musical melody when the key is left in the ignition with the door open and engine off.
and
3 - a general quick bleep when the fuel is low, washer bottle is low, or the trans is put into drive with a door open, as well as other general issues.

Now here is my issue.

If I start the car, shut all the doors and drive off, I get the 3rd bleep after about 5 minutes of driving, with no warning light to tell me what it is. It only does this once, however it has done it twice on me on one occasion.

Can any one shed some light as to why it might be doing this?

Any ideas would be greatly appreciated, cheers :)

I am frustrated because I dont know where to start looking for the cause of it.