I thought it was just a loose alternator belt, but now after charging the car and fixing the belt, the starter doesn't do anything at all, or draw any power. I measured the voltage of the small wire going to the starter and got 11.3V in Key Position II and 11.8V in KPIII. I thought that was weird, I thought the voltage would only be present on KPIII. I have the wiring diagram for this model, and there's a wire bypassing the neutral safety switch which I find bizarre, I feel like I am reading it wrong.

I think that the lights go out (or dim a LOT) during starting because the starter draws a LOT of current,

Perhaps your starter is not getting its electrical jollies.

This could be as simple as a bad primary wire.

I noticed a lot of corrosion at the positive battery terminal of our '90 744TI.

I found that most of the copper strands were gone. I had to cut the wire back and solder it into the battery terminal.

the NSS neitral start switch,,use a crevu=ice toolfro s hop vac tclean out any debris innit &if need be sprays it w KB blabster??

The bypass jumper shown at connector C166 (on the tunnel in front of the relay tray) is present only for manual transmissions in place of the PNP safety switch on the left side of the automatic trans shifter assembly. There's also an optional component shown 18/5 'transfer alarm' similarly in that circuit supposedly for USA/Cdn/Japan models, but I don't recall it nor is it pictured in the schematics. Note in the green manual wiring diagrams that dashed lines indicate the connection/component may only be present on certain models, in select markets or with certain features. You often have to think a bit harder as to which models and features this might apply to as there is generally no written indication.

After verifying your battery has a good charge and that battery to chassis/engine ground is good, you can then start by jumpering battery +12V directly to the starter solenoid terminal to see if it cranks/clicks to determine whether it's the starter/solenoid or that you need to do further problem isolation between battery +12V, the ignition switch, the neutral safety switch, and the starter solenoid. If no starter action or just a solenoid click, try striking the starter casing hard multiple times using a rod or hardwood dowel and a hammer trying to move the starter off of any dead spot. I'll often just start tapping on it hard with a piece of 2x2. If it works, I'll then pack it in the car until I can get a new starter so as not to get stranded. Such starter problems are often intermittent and you can keep that tapping game up for a number of weeks. If tapping doesn't work, then confirm that +12V is reaching the solenoid via the ignition switch to confirm it's the starter.

It is not at all uncommon for our vehicles of this age to have a bad PNP safety switch or a worn ignition switch. Try rotating the key back and forth rapildy and twisting it a bit harder to see if that now establishes contact (of course without breaking the key). Try starting while you move the trans shifter back and forth a bit and also side to side, especially pressing the shift lever hard to the left.

That loose female spade connector on the short pink wire that Bill mentions (for use with a mechanic's remote starter switch) is in the left fender wiring harness. It bypasses the ignition switch, but does not bypass the PNP safety switch. It's a very convenient test point for diagnosis to determine if it's the ignition switch. You can put a meter on it and if you see +12V when you try to start with the ignition switch then the ignition switch is okay. If you apply +12V to it to try running the starter, if it then cranks then the PNP switch is okay.

If it's the ignition switch then do further reading here on how best to get at it, such as removing the instrument cluster for better access to the two slotted mounting screws you can't see that can be a bit of pain to get at and remove.

If it's the PNP safety switch then they can often be opened up and cleaned to restore functionality. It's a bit tricky to gain proper access and remove the switch from the side of the shifter assembly without breaking the thin plastic mounting pins. Check out the FAQ here for tips on doing this, but some of the better information is in this forum in older thread replies. Post back here with a reply if dealing with this switch becomes an issue for you and we'll try to give you some tips, especially with the later 1994/1995 trans shifter assembly.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

What DC volts at the battery?
Inspect/clean/service the battery terminals for good luck.

There should be no Rube Goldberg jumper on the interlock switch.
Insure that the interlock wiring and switch is OK.

Test the starter solenoid and Battery by applying +12VDC to the service socket,
item 17/1, a single pole connector with a pink wire inside the engine bay
up high, between the headlight and firewall. Look in the harness near the OBD port.
(Maybe this wire is what bothered you in the wiring diagram? It's a service port to start the engine)

The ignition switch is another item to check.

Cheers, Bill

Thank you for the location info, I'll try that diag port next. The jumper wire for the neutral safety switch is indicated in the wiring diagram, it's a little loop, with a P label for the wire