Wouldn't start, had to be towed home

[Aaarrghh]

What page of the manual are you looking at, for that adjustment?

Anyway, there IS a switch on the transmission that's linked to the shifting mech, with 4 wires going to the conduit tee in the photo. I assumed it was the neutral safety switch. What else would it be? I looked it over good and inspected the wires -saw nothing amiss.

Winnebago put the shift handle on the dash. A motorhome chassis might be different from a regular truck chassis, and have the switch elsewhere.

I've held the key over to "start" and moved the shift handle all around, to no effect

I suppose I'll eventually have to ask my wife to come out and turn the key, while I lie underneath and probe the solenoid connections. I'm sure she'll have plenty of advice  W%

[M & J]

Back up light switches are mostly mounted to the trans.

[Aaarrghh]

Back up light switches are mostly mounted to the trans.

That would explain the 2 light gauge wires, in addition to the 2 thick ones I'm assuming are for the starting circuit.

The thing is, I do have a start voltage in one wire going into the tee. I'm going to pull the tee apart and trace that wire.

Got my new cooling unit sealed into the box, ho ho 

[DaveVA78Chieftain]

If the gearshift is on the dash, then I agree the switch is on the transmission.  Was just passing on what the 1983 Service Manual was stating.  If the switch is mounted on the transmission, then it is most likely a combo Neutral Safety and Backup switch.

[Aaarrghh]

If the gearshift is on the dash, then I agree the switch is on the transmission.  Was just passing on what the 1983 Service Manual was stating.  If the switch is mounted on the transmission, then it is most likely a combo Neutral Safety and Backup switch.

Thanks, Dave, I do appreciate your efforts to help. I tried deciphering that wiring diagram. I got nowhere. It's great you can. 

I did a little more wire tracing today. Things aren't as simple as I thought. No wires from the switch go down to the starter. 4 wires come up, 3 are always hot. I'd expect the other (the big pink or light purple one) to be what activates the solenoid. (1st photo)

Tracing the conduit/purple wire to the front of the vehicle I find this gismo (2nd photo). What is it? Is it a relay? Notice the electrical tape around 2 wires. The insulation under the tape was stripped off. Could that be so someone could jump those wires? Should I try that? Is it placed up front so a service tech could connect something to it? It seems placed to be easy to access.

I didn't trace the wires from the neutral/backup switch. I'll do that tomorrow. Maybe that will provide a clue. They do get voltage when the key is turned to start.

[DaveVA78Chieftain]

Wire from ignition switch to starter solenoid "S" terminal was originally a purple wire.
GM had a hot start issues so in later years they added a relay on top of the engine near the alternator.  The purpose was to ensure there was minimum voltage drop on the "S" lead (purple) to the starter solenoid.  I suspect that is what you are seeing.
The purple "S" lead from the ignition switch was routed to the coil of the added relay.  Other side of relay coil was grounded.
One of those leads from the B+ terminal on the solenoid was routed to the one of the relay posts. 
The other post was routed back to the "S" terminal on the starter solenoid.
So, when the ignition switch was placed to start, the relay coil was energized which allowed the voltage from the B+ terminal to be wrapped back to the starter solenoid "S" terminal.

[Aaarrghh]

  SUCCESS!  On a whim, I turned the key and the starter engaged. That was after handling the relay and probing the wires to it. So I filed and greased the contacts, and fired'er up!

Just goes to show what trouble a few oxidized contacts can cause.

Thank you all for being so helpful, especially Dave. It's so good to have people to talk things over with. 

[DaveVA78Chieftain]