OT -- Question for Ray O

Ray, I have a Mazda MPV (1993) that shifted into 2nd (maybe 3rd) on the freeway and stayed there. Now, the starter won't go, and the car will not go into any other gear beside whichever it is stuck in. (While the motor is OFF, the drive train is locked up as though the trans is in Park, but I can't tell if it really is in Park, or if there is a mechanical way for the trans to lock up even while the motor is not running.)

In any case, my gut instinct is that the Neutral Safety Switch is my problem, so I removed it and opened it up.

My question is, what is the complete role of the NSS? It has far too many contacts inside to simply control starting the motor in P or N.

STUFF I KNOW ... I THINK there is a sign of contact burning, or at least a very dirty contact, but the contact in question is not one of the P or N contacts. It looks to be one of the D contacts. I can clean the entire switch and refill it with dielectric grease, but frankly I am treading in unknown waters here. I don't see any opportunity for further damage that I can cause, but I want to know what other sorts of things the NSS does.

I'm sure there are internal problems that may exist, but my hope is that all of my troubles are in the NSS. The van has had trouble starting lately. When the key is turned, there is a click (a single click), but when the key is turned again and again, the starter normally fires very strongly. I don't have any worry about the battery -- the battery guy has tested it good -- and the starter works very strong when it works. I hadn't considered the NSS as the source of my starter troubles until the transmission quit working.

I was driving on the freeway at about 60ish, and when I accelerated to pass somebody, the trans downshifted out of OD. It occurred to me that the downshift was not needed at the time, and that it went a gear too far. I knew something was wrong though when it did not shift back up to OD when the pass was completed. The motor was only turning 3K at the speed I was going, and Red Line doesn't arrive until somewhere over 5k, so I continued to my destination. When I parked, I tested R, and it would not go there. So, I thought that the guy I was going to see at his office could help me push the van out of the space, and I could limp home. The car would not go backward -- it feels like the trans is wanting to move the car in a forward gear, I assume 2nd. I turned the motor off and tried to push the car backward, and it would not go -- the drive train hits a physical hard-stop as if it is in P. Now, when I try to start the car, the starter circuit -- the low current stuff inside the dash -- only clicks. The starter makes no effort to spin or fire the solenoid (which is why the NSS is on my bench right now).

Reply to
Jeff Strickland
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First of all, I'm assuming that the the MPV has an automatic transmission, and when you say that the starter "won't go" you mean that it does not engage.

With the motor off, the transmission pump is not pressurizing the transmission so it is possible that pistons, clutch packs, etc. may not allow the drivetrain to move.

The neutral safety switch's main purpose is to prevent power from going to the starter unless the transmission is in neutral or park. In some cases, it also prevents the ignition key from being removed unless the vehicle is in park. I have never heard of a neutral safety switch affecting automatic transmission shifting.

There are other transmission-related electrical functions that the switch may or may not be serving, like gear indicator lights in the instrument cluster, gear range signal for an electronically controlled transmission, cruise control cutoff, etc.

There has to be an electrical wiring diagram for the NSS so you can check it electrically. That is the only reliable way to check it out.

I think that the van has 2 problems. The incorrect gear problem is probably unrelated to the hard start problem, except that if the transmission is jammed in gear, the starter will not be able to overcome the jammed transmission, or you have some kind of unrelated starter circuit problem.

I don't know anything about your transmission, and whether it is electronically controlled or hydraulically controlled. If it is hydraulically controlled, there are a lot of things that control what gear the transmission is in, including gear selector position, output shaft speed, engine speed, throttle position, and in some cases, manifold vacuum.

If it is electronic, it could be something as simple as a stuck or bad shift solenoid or as bad as a cooked transmission.

If you want to check whether the neutral safety switch is bad, just bypass the switch and see if the starter gets juice.

Reply to
Ray O

Yes, it does not spin or engage.

That's what I'd always heard -- the only function is preventing starting in gears other than P or N. But, after taking the switch apart, it clearly has other duties.

The gear selector is a simple flag that is tied via a string to the shifter. Simple stuff there. The NSS appears to have a job feeding electrical stuff to the transmission controller. The switch does not actually go inside the trans, but there are clearly contacts that feed signals to the trans depending on the position of the shift lever.

Yeah, that's what I thought. Given enough time and a working system, I could probably figure out what wires/signals go where, but I haven't the inclination to go that deep.

Now that's certainly a possibility. I'm not sure that is the problem because the noise(s) don't seem to support the theory, but I had not even considered that one. It could be the trouble with the starter ...

Thanks, I pretty much did that. I've decided I'm in over my head. The Transmission Shop will be getting The Call on Wednesday when they re-open from the holiday.

And, it's an electronicly controlled unit. I'm surprised it can lock up without any hydraulic pressure.

Reply to
Jeff Strickland

If a shift solenoid or spool valve is stuck, then something may be jammed.

Good luck with the repair!

Reply to
Ray O

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