[smoothie3]

91-940 Turbo;
upon starting; mysteriously the 4th gear lockout indicator light lights, after a few miles, most of the time I can put my foot down and kick in the turbo...4th gear lockout light goes off, everything is fine. OR, OR the lockut indicator does not go out and my battery will drain while driving or, if I stop and shut her off...will completely drain battery within 3-10 minutes. For years I have been able often to push the tripmeter reset and the 4th gear lockout light goes OFF instantly/all is well! Or as the original owner had showed me, occassionally a hard thump with my hand, top right side of the dash right of cluster. In the past it seemed to be related to tempurature and/or humidity, but after 3-4 mile I could get it to turn off that 4th gear light, Not any more.
Sometimes turning on the lights will "dim" the 4th gear indicator and it seems to correct the problem; I can tell if I have NO drain by activating the windshield washers...full force = ok, slight washer pressure= still shorting/draining.

Seems like a short in the instrument cluster, never smell hot wires, but can drain very quickly

I always carry a spare battery and extinguisher.
Grand old 91, 940 Turbo w/265,000

Any thoughts or links to fixes will be kindly considered.
Many thanks, Stacy

 

[dwsweck]

try replaceing the overdrive relay,that can cause this light to stay on.have the charging system checked too,the voltage regulator brushes could be worn out,

 

[smoothie3]

got it!

After years of dealing with this;

I finally discovered that my alternator was not getting "excited" enough in order to kick in the alternator until I reved up the engine to 3K rpm or jumped the alternator (little post) with a hot wire from the positive side of the battery. I have since installed a switch in the cabin to make a quick contact with a hot wire to the alt.

The instrument cluster is supposed to do this for me but even after refitting the indicator lights in the cluster, it was still a sporatic condition.

All's well now, as long as I recognise the 4th gear lockout indicator light coming on when I start it so that I can manually excite the alternator by reving it up or jumping the alternator with the extra juice required to get the alternator to kick into the charge mode.

Still doesn't explain the unbelievablely short time it takes to completely drain the battery though. Like a couple minutes or less?

I hope this might help someone else with similar a issue.

Be well,

Stac