Bad Neutral Safety Switch?

[Carl Stouffer]

I am in the process of replacing my neutral safety switch and I think I got a bad (new) switch. It is a Standard NS-15, new in the box. After installing it, I tried starting the coach and, instead, heard a sizzling noise and saw a bunch of smoke coming out from under the dash. I removed the switch and unplugged the wiring harness, turned the ignition to the start position, and (of course) nothing happened, including no wore frying.

I then connected the wiring harness plugs to the switch, off the column, and the wire (one of the two on the angled plug) fried again. Now I need to repair that wire, PLUS replace the switch, but I'm wondering if anyone else has run across this scenario. The only thing I can figure is that the brand new switch is bad.

Any other ideas?

 

[Bhart]

From Jerry works:
2) at the top side of the steering column near the floor is a switch with two purple wires on one connector. One of those purple wires comes from the start terminal on the key switch carrying 12vdc when the key is in the start position. Check with a meter to find that 12vdc hot wire. The other wire goes directly to the starter solenoid to energize the starter. The switch those two purple wires plugs in to is the neutral safety start switch that is there to prevent the coach from starting unless you are in park or neutral.

3) if you do not find 12vdc on one of those two wires then the key switch is suspect and you will need to buy a piece of 12ga wire to "hot wire" the coach to get it to start. Be careful to be in neutral or park!

4) if you do find 12vdc on one of those wires, then buy two male clamp on spade terminals and a short piece of 12ga wire to make a jumper to bypass the neutral safety switch. Again, be careful to start only while in park or neutral.

5) if the starter solenoid still does not energize the starter with this jumper in place, then either the purple wire going from the neutral safety switch to the starter solenoid is broken or shorted, or you will need to replace the solenoid and/or the starter. Either way you need to crawl under the coach with a volt meter. Be sure you are in park with the e-brake set! Remove the wire going to the solenoid and see if you have 12vdc when the key is in the start position. Is you do, replace the solenoid and/or the starter.

 

[LQQKatJon]

Fairly simple circuit. Must be grounding out the purple wire??

NEUTRAL START SAFETY SWITCH ISSUES

www.gmcmhphotos.com

Meter should tell you what that switch is doing?

 

[Carl Stouffer]

The problem I'm having is with the black wire on the plug in the pic, below:

PNSS from passenger side

Trying to show the location of the starter solenoid enable switch connections so you know where to jumper if diagnosing a starter problem. This side of the switch has the connector for an Electro-level timer relay and is enabled when the shifter is in the 'Drive' position

www.gmcmhphotos.com

 

[LQQKatJon]

The problem I'm having is with the black wire on the plug in the pic, below:

PNSS from passenger side

Trying to show the location of the starter solenoid enable switch connections so you know where to jumper if diagnosing a starter problem. This side of the switch has the connector for an Electro-level timer relay and is enabled when the shifter is in the 'Drive' position

www.gmcmhphotos.com

According to wiring diagram. Black should be grounded. Says it should be grounded to same grounds as instrument panel grounds.

 

[LQQKatJon]

According to wiring diagram. Black should be grounded. Says it should be grounded to same grounds as instrument panel grounds.

Wiring diagram has that black wire grounded. The brown wire on that connector comes from the electrolevel system. From a relay/time delay.

 

[Carl Stouffer]

Wiring diagram has that black wire grounded. The brown wire on that connector comes from the electrolevel system. From a relay/time delay.

There is a blue wire and a brown wire on the same terminal and a black wire 90 degrees on the other terminal on that same plug. If the black wire is a ground, why would it be energized enough to fry when the switch goes into the start position?

I plugged in the old switch, which is hooked up exactly the same way as the new switch, put the switch tang in the neutral position and the starter engaged and cranked the engine with no drama. It also worked at a certain point in the "park" position.

I'm going to take both switches down to my mechanic friend tomorrow to see if he can figure out the difference. The guy is a wiz with electrical stuff, an area where I am somewhat lacking.

 

[Carl Stouffer]

So I got the neutral safety switch problem sorted out. Took the new switch and the old switch down to my mechanic's and he took both of them apart. It seems the new one was faulty. The traces inside were evidently touching and that's where the short was coming from. Jim ended up cleaning and lubricating the old switch and putting it back together.

I re-installed it, along with repairing the burnt wire. I had a little difficulty because one of the clips that holds the switch to the column had popped off and it took a while to get it back on. I finally managed to get it snapped back in place with a pair of channel locks. The coach once again starts in Park, but I still need to do a little adjustment to get the neutral position correct.

Now on to bigger, messier things (re-packing the rear wheel bearings and flushing the brake lines).