only 2 electrical gremlins left...rear power locks and cruise 90 240

So I have fixed numerous issues with my car since I bought it. Parasitic drain, repinned ignition switch by previous owner, non working speedometer, odometer, radio, power locks, and power staying on after ignition was off for circuits 1-3. Well the car is now running at 100 percent, all maintenance done, new suspension, AC update with parallel flow condenser, every fluid leak fixed, plus quite a few updates. Now all I'm left with are the rear power locks not working, which is weird because they did which I first fixed the power locks. Oddly enough they worked and the passenger lock didnt work. Fixed it and then the rear locks stopped a few weeks later at the same time. Any ideas? Just looking for a common issue before I pull the panels next weekend.

The other other issue is the cruise control. I have had my cluster out about 30 times and the dash has been pulled but the cruise never worked(then again the speedo didn't work when I got the car). Is there a test procedure for the speedo? Are there any wires that can be unhooked on the cluster that can cause this? I know my brake switch works and it is an automatic. Can the neutral safety switch cause an issue? It randomly has problems but I have bypassed it through the engine bay(I have a manual swap planned so I didn't want to buy a new one).

The cruise control does get a signal from the speedometer. If I recall correctly it is one of the single wire connections near or on the back of the speedometer. If it's not connected and the cruise has no speed signal then it won't function.

For the locks since it's only the back doors. I'd look at the wiring manual which will show where the harness goes. Find the places where the harness junctions are and check the connections there first. Plus you can use those spots to ohm out the wires.

Cruise

Easiest things to check are the brake and clutch switch. Make sure the switches have power and read closed circuit with the pedals released.

The cruise is a vac system that has it's own "ECU" right by the steering column iirc. The brake switch can be adjusted and should obv be pressed closed with the brake at "foot off" position.

If you find that ECU (or a wiring diagram) I think there are 2 plugs on it. One plug comes from the turn signal stalk and one goes to the speedo cluster.

If your speedo doesn't work, you should start with that because that will negate it. If the speedo works and everything is getting the power it needs, check to see if it will hold vacuum. Make sure the ball and socket joint is hooked up to the gas pedal as well, and that things are anchored properly there. The pump that runs it is on the left side (US drivers side) right by the hood hinge. Looks kind of like a wiper motor.

I added cruise to my 93 245. All the wiring was factory installed. You just needed to add the vac system, the signal stalk and the ECU for it to work so... I would optimistically say that that wiring should've remained untouched.