Speedtoys

Im pretty sure that em chasing false positive warning on a lose TB light.

What things might leads to this I need to diagnose?

jcorenman

Easy stuff first: Check the connector on the timing-belt cover, near the dipstick. If the harness wire is led incorrectly, putting the connector under stress, then it can make intermittent contact. The factory used small-diameter vinyl sleeving to protect that wire, and that sleeving turns hard and brittle after 30 years which also stresses the connector. Ditch the brittle sleeving, if the wire insulation is soft and flexible then just go with that.

Make sure the backside of that connector-- a pigtail to the male spade-connector on the tensioner arm-- is secure and tight. (Remove the pass-side TB cover and peek inside the plastic center-cover). That connector/pigtail is replaceable, 928-606-148-00, around $15).

On earlier S4/GTs (pre-89) there was a metal strap connecting the tensioner to the spade connector, this sometimes fatigues and breaks. Later S4/GT/GTS's have a wire jumper (928-607-110-00), much better for around $3. Getting to this requires removing the center-cover, so if you see a metal strap then swap it for the wire jumper.

Mrmerlin

for false light events i also found that the isolator bushing that rides on the piston if its original,
can crumble and pieces will break off and fall into the bottom of the well that the piston pin sets in,
these small pieces can then get caught on the tip of the pin and cause the belt warning to alarm.
Its happened two times to me now i replace this part when doing T belt jobs.
Also look into the tensioner shaft pivot bushing being worn.

WICruiser

I chased this for a while and finally determined in my case it was the connector on the front of the center belt cover. The pin and socket connection was not secure enough, apparently due to spreading of the socket but I couldn't find a way to tighten the socket diameter so I used a few strands of copper wire from a 16 gauge multi-strand wire inside the socket to tighten the connection.

BIMMERMIKE

Does the center belt cover need to be removed to get to pigtail to male spade-connector on the tensioner arm?
I'm experiencing a belt tension light on but have checked belt tension 4-5 times and tension is always good(same)

Speedtoys

Lots going on here...as I nearly had a Tbelt fail last Sunday.

BIMMERMIKE

Can you tell us more?

Speedtoys

Something froze, belt was slipping and burning, shut it down before it broke.