"Ping" from Under Dash

[coldwar]

Just yesterday I noticed I am getting a "ping" from under the dash- driver's side, sounds like a relay switching. At first I noticed it happens when I'm braking to come to a complete stop, then I noticed it happens if I'm rolling to a stop without necessarily braking too. It happens when the car has slowed to <10 mph. Wierd! Everything else is normal, and there seemed to be no battery drain overnight, so I don't think any circuits remain stuck on as a result of this. Any ideas what it could be? Keep in mind my car is W115, so may be different than what y'all are used to.

Dave

1976 300D "Pearl"
1970 Euro 200 parts car "Earl"

[dieseldiehard]

could be the cruise control module dropping out as speed drops below a certain threshold? I believe it senses speedometer revs - this is just a hunch. I had a 115 diesel but never noticed anything like that.