1987 RV Engine Won't Turn Off

As crazy as this sounds, start pulling fuses. I had a new Chevy Tahoe do that many years ago. It was the daylight running light fuse circuit. Somehow a diode had shorted and was back feeding the circuit.

Please delete

Doubtful I can actually help, but anybody who wants to take a crack at this will need Year, Make, Model and Engine of the Chassis, not the Coach. Chassis year may not be same as Coach Model Year and who knows what Year it's registered as.

I believe it is a Chevy Chassis with a 7.4 Engine, I can only assume the year is the same as the rest of the RV however that I won't know till I am able to get over to my RV and look.

Since we did replace some bad fuses at the same time as the other stuff when I get to my RV I will try YC 1's suggestion and see if it works first, because I did notice even when the engine was off and all the doors were closed that some of the lights near the dash stayed on like the power step dash light and another light that I had to unscrew the light bulb from so it didn't drain my battery.

Won't be able to try it until tonight so keep the suggestions coming so I can try multiple tonight if his doesn't solve it.

I don't know if this might help but.How are the ground's check too see if they are good,it might be a good idea to even make a new one some where on the chassis from the battery. I found on my 1988 gulfstream coach that I just purchased that the grounds are bad so I've redone all most all of them through out the coach.

On older vehicles this is usually caused by 12v power still getting to the coil even after the key is removed. The coil is the thing that changes 12v to a very high voltage so the spark plugs can work.
I wish I was more familiar with your particular engine but since you already changed the switch (first of my idea too) you may want to see why there is power still on the "run" side of your circuit before you start back up again. The lights staying on is hinting to me that something is still allowing power into that side of the circuit breaker panel even after the key is removed.
The key should have an Accessory position which usually turns on most systems like the radio and even the lights. A Run position which is the position that the key is normally when driving that will keep the accessories on and also give power to the ignition circuit which powers the coil. And a start position that will turn off most accessories while giving most of it's power to the ignition circuit and the starter motor circuit.
These positions have separate areas on the fuse panel and I suspect that somehow 12v is being accidentally back fed into the ignition side of the fuse panel and apparently all the time.

Yep sounds like a cross circuit short
Start pulling those fuses you replaced
Eventually you will need to repair what is bad or do without it

Yeah the coil wire (pink and green if I remember correctly) right where it plugs into the spark plug area is the wire I have to unplug every-time to get it to finally turn off.

So if that means it is a fuse issue what is the best way to test this?
Turn the engine on, then put the key back in the off position, and then just start pulling fuses until it finally turns off?

Any particular fuses to try first? Should I start with the fuses under the hood or the ones under the dashboard first?

OK... The cross-short idea... Any recent work? Including driving screws or nails, jacking, blocking, something that could pinch or rub a wiring harness?

My uncle owned an old-timey auto electric shop and told me to always look for recent work and mods by the owner when chasing an electrical problem.

Do you have daylight running lights? If so, pull that fuse first. It would be interesting if it was the same problem I had. I am a Senior Certified Electronic Technician so these things get my interest up.

It can be a real bear chasing something like this down even with a decent schematic which probably does not exist.

Once you find a fuse that cures the problem, then put it back in and keep pulling fuses to be sure there are no others contributing to the problem.

As suggested, a screw wearing through a harness can be a monster to find.