'94 100 stays in 3rd

[Kent McLean]

car: my old '94 100S Avant, V6, automatic, non-quattro.

The SO's son now reports that the automatic won't shift out of third.
 From what I can gather, he can move the shift lever from park to drive,
but it seems to start off in 3rd (he can't feel a shift from 1st or 2nd).
It won't upshift to 4th.

He can down shift from drive to 3rd to 2nd, but it stays in gear (he
thinks 3rd; he can do 40 mph, so it definitely isn't 1st).

This just started after he replaced the turn signal switch, which meant
the steering wheel came off, the airbag came out, and the switch the
includes the cruise control switch were removed. Related?

Now that I'm thinking about it, is third gear some sort of limp-home mode?
Can it be re-set? (Prior to this he pulled the battery to try and get
the alarm system resynced, to maybe fix the turn/hazard problem.)

He checked the fluid, it seemed OK, and he didn't add any. After the fact,
I told him Audis are particular about how you check the transmission fluid,
although I don't remember the sequence (up to temp, in park, engine running?).

This no-longer-my-car is going to be the death of me. And it had been the
"old reliable" one.

-- 
Kent McLean
1999 A4 Avant, V6 Tiptronic
1991 200 TQA #3, with mods
1990 V8 w/5-speed and other mods
gone: '91 200 TQA x2, '94 100 S Avant, '89 200 TQ "Bad Puppy"