2002 Diplomat, Won't Start, No "N" In Trans Selector

[TimWright]

2002 Diplomat, won't start. Also the N in the transmission pad doesn't light (the little red "economy" light is on, but nothing else). Also the step won't run, the power mirrors don't work, and the power seats won't work. All of this, all at once.

The dash lights up, fuel pump comes on, dash AC blower comes on, headlights are bright. I had the batteries tested and they are fine. I have checked every fuse I can find, including the 2 in the VIM and they are OK. This has to be a power supply issue since so many things out all at once and all of them power through the armrest where the transmission selector is.

So, there is either a fuse I cannot find, a connector corroded, or it is a relay but there are so many relays! Which one?

Where to look for any other fuses?

Cummins ISC and Allison transmission.

[hermanmullins]

Tim,

Sounds like a starter solenoid. 

Herman 

[TimWright]

That is what I was thinking initially when it wouldn't start, but then I discovered all of the other things not working - essentially everything with a switch on the "armrest" where the transmission panel is. Do all of those things run through the starter solenoid? It wouldn't seem like they would, but who knows how/why things are wired sometimes.

[manholt]

Tim.  Welcome!

Have you checked the start switch in the rear of your coach?  It may be off !

Carl

[kaypsmith]

9 hours ago, TimWright said:

This has to be a power supply issue since so many things out all at once and all of them power through the armrest where the transmission selector is.

Tim, your chassis batteries are the power supply. This will be either a fuse, or relay, or a switch, or a non grounding issue somewhere. Could be as simple as poor ground to the transmission, since the neutral light is not showing up, but I wouldn't think that would be the case since all the other items are not working. I found a bad ground to the ECM on my coach causing havoc in the past. Also, you said that it won't start, does this mean it will crank over with the starter, or does the starter refuse to engage?

[TimWright]

All the switches are on. 

When I turn the key on, the dash lights up, the gongs sound, the "wait to start" comes on and then goes off in the normal time frame. Everything acts as normal until I turn the key to the start position and then, nothing - no click, doesnt crank, no sound at all. I am told that since the N light isnt on, the transmission wont allow it to start. So, I think it is a matter of getting power to this to get it to start.

I have looked at all of the fuses I can find and they are fine. I got my power probe out and checked the solenoid that is in the box on the driver's side up front and all of the terminals read that they are grounded. None of them are hot. Not even the one marked "+" and this is true even with the key in the "on" position. Does this mean the solenoid is bad? Or am I not testing it properly?

Bad ground or loose connection certainly possible, but so many wires and connections to check! Must be an easier way...

Weirdly, tonight after messing around with it yesterday, suddenly the step and the mirrors are working! The power seats still not though and of course it still wont start and the N light isnt on. Also, there is a whole bank of fuses, which include the seats and other things, which is getting no power either. Fuses are good, but neither terminal is hot.

Not sure if this helps to or not. All help is appreciated!

Thanks

[hermanmullins]

Tim,

Two Solenoids.

One solenoid for Start.

One solenoid for accessories.

Power to both from same source.

Try checking both. With key on both large lugs on each solenoid should have 12 volts. If either doesn't one doesn't have 12 volts on both, check power to small lugs. One is ground and the other is 12 volt power to activate the solenoid.

Herman

 

[kaypsmith]

Is the gear selector push button, or slide selector?

[wolfe10]

2 hours ago, kaypsmith said:

Is the gear selector push button, or slide selector?

With the Cummins ISC, he will have the Allison 3000 and Monaco used the push button/electronic membrane pad gear selector so common with that transmission.

[kaypsmith]

In that case, is there a transmission electronic reset? Not likely that the neutral switch has anything to do with the power seats, but will certainly prevent the start solenoid from engaging, and since the neutral light is not lighting. Also the key switch may be showing wear, since other items mysteriously started back to working.

[TimWright]

All,

In answer to your questions/comments;

Yes, push button trans selector. No idea if or where there is a reset button. Any ideas? The backlights on the keys are on, but the N for Neutral is not. My understanding is there are two power supplies to this and if so, I think one of them is out and probably the same thing supplies power to the other stuff.

To be honest I am more bothered that some of the stuff started working than if it had not because to me that suggests a loose wire that I wiggled and got right, which will mean checking every one of the million or so connectors. Or, it means that there is an issue with the circuit board on in the box below the driver window. Or a short, maybe in the big circuit board? But that is me guessing...

Herman - 2 solenoids, check. I have found one, and it is in the box below the driver window. No idea where the other one is. Any help?None of the 4 lugs read any voltage at all even with the ignition key on and all the dash lights on and the gong sounding, and the fuse in it is good. So, sounds like this is the culprit?

This solenoid is on a big circuit board that has about 40 fuses on it and one section of about 10 fuses has no power to either terminal of any of those fuses, which probably not coincidentally, includes the seats. Sound like this is my guilty party to you? So, is this an auto parts store item or go to my nearby RV supply store (I have a State Trailer Supply nearby.)

Again, thanks all. Sorry if I appear slow, I just dont want to replace parts unnecessarily and I dont want to do more harm than good.

 

[manholt]

Auto parts.

[kaypsmith]

The start solenoid should be located near the starter itself, large battery wire going to it and a large one going to the starter unless it is made onto the starter in which case only one large battery wire, also one sometimes two smaller wires, one of these goes to the next control between the key switch, this control should be near the key switch. This control may be checking for all systems including the neutral switch to report all systems are ready before allowing the start solenoid to activate.

[TimWright]

All, I appreciate your patience and assistance.

So, here is what I learned tonight; I pulled the solenoid from the box below the driver window. 

It has one large terminal that has a large cable that goes to a terminal labeled "Interior Fuse panel" on the circuit board and then a small wire that has a fuse in it and goes to the small + terminal on the solenoid.

The other large terminal on the solenoid has a large red cable that goes into a bundle that goes who knows where because I cant trace it but I think it goes to the back of the bus somewhere. To my thinking, this wire should be hot, but when I put my power probe on it, it shows it is grounded. So, I am thinking it needs something to happen to energize it and that whatever the item that does that is the problem. It reads grounded when the ignition switch is on or off. Seem like it should be hot...

The "-" terminal on the solenoid has a pink tinged gray wire that dives into a large bundle that goes to???

I took it to the auto parts store and they hooked it to a battery charger and got it to click and to operate a light. He said it was working but thought it might be sticking a bit. (I reinstalled after this hoping maybe it had been stuck and was now un-stuck...no luck)

So, how does this solenoid get power? Clearly it should be from the big cable that goes into a huge bundle and goes to who knows where? But it does not read hot on my tester. It shows it is grounded. What powers this wire?

As an aside, or as a key piece of information - you tell me, this solenoid has two labels on the circuit board; "isolator relay delay" and "aux start relay" 

Also, there is a solenoid looking device in the battery box that is labeled "coil." Is it? And could it be the issue? And, associated with this is a rectangular black box about the size of a box of tick tacs made by Omron - what is this? And more importantly, might it be to blame?

As for the starter solenoid, have not found it - suspect it is under the bus and getting there is difficult.

Ok, hope this helps you hone in on the issue. 

 

Thanks

Tim

 

[hermanmullins]

Tim,

Solenoids should have  two (2) large Lugs and either one (1) or two (2) small lugs. Those with only one(1) small lug, are grounded through the solenoids case to the mounting place. Those with two (2) small lugs have have a ground (most of the time white) and a hot (most of the time black). the hot wire get it power through the ignition switch. When the key is turned on it sends power to the solenoid which then closes the open solenoid to complete the connection between the two large lugs, there by sending current to the correct power panels, starter, and many other locations.  You may notice that one (1) of the large lugs is always hot while the other one is not until the key is turned on. Notice that the other large lugs goes to a fuse panel that cover an array of different areas.

If when the key is turned on you should have power to both large lugs and one(1) of the small lugs. If the small lug has power but only one(1) of the large lugs has power then the solenoid is bad. However if the small wire does not have power when the key is turned on then you may have a defective ignition switch. 

One thing you could try would be to connect the two(2) large cables on the solenoid together and see if your engine will start and your panels light up.

Hope this helps. Sometime it is difficult to explain without being there.

Herman 

[manholt]

Tim.

There is a button or switch, mine is on left side of steering wheel on dash, that says AUX.  When my starter batteries was going bad and did not have the amps to start the engine.  I pressed the aux switch and it started right up (it uses the house batteries as a boost).  Herman snuck in!

I suspect that the solenoid you pulled was for auxiliary start.  I also think you have a dead cell in one of your batteries. 

[jleamont]

Tim, on ours under the rear floor in the closet (above the transmission) is three of these solenoid's (similar photo below), these power different parts of the coach. I also have more in the right rear compartment power distribution center. Check those, You should have power on one big lug and a ground on one small lug, when the other small lug gets power it closes inside and energizes the other large lug. If you have power across both large lugs its on and working.

[TimWright]

Herman, yes it is like trying to tell someone how to set their VCR over the phone. (LOL), So, I appreciate you hanging in with me.

The solenoid I pulled from the box under the driver window has 2 large lugs, and 2 small. Of the two small one is labeled "-" and one is labeled "+". The "-" has a small wire that goes into a large bundle that seems to head to the rear of the bus (hard to tell once it goes through the box). The "+" lug has a wire with a fuse in line and connects directly to one of the large lugs. This same large lug has a large cable that goes to a terminal on the circuit board labeled "interior fuse panel". The other large lug has a large cable that goes into a large bundle and appears to go toward the rear of the bus, but to exactly where I dont know. I think this wire should have power but it does not. None of the wires have power, and clearly at least one of them should in order to power this solenoid. But, none of them have power even with the key on. So, tying them together wont do anything - they are all dead. I could run a lead directly from the battery though, if that would be safe. (I am not worried about getting injured, just about giving something more voltage than it needs and frying something expensive.)

So, I think the question becomes, what causes that large cable from the back of the bus to become hot? I can understand that maybe it should not be hot all the time and that something should happen to "turn it on, " but what? If just turning the key in the ignition switch should make it hot, it isnt, so maybe it is the switch, as you suggest. But, if turning the key is supposed to trip another solenoid that then allows this cable to be hot, then it must be this other solenoid that is bad. Wherever it is...(have not crawled under the bus yet to get at the one on the starter, and did not pull the panel in the floor of the closet, but will do so and see if i can see solenoids from there - thanks jleamont)

Manholt - I think you are right, that the solenoid I pulled is for the aux start which ties the house batteries to the chassis batteries in order to "self jump start" the engine. Maybe that is all that it does, but since it has a cable that goes to a terminal labeled "interior fuse panel" I suspect it also powers up some things as well which would explain why there are other things not working. I pulled the batteries and had them tested and they are ok. I suppose I could still have a bad cell, but the headlights are bright, the dash ac blower strong, and so forth. But the N on the trans selector isnt on, so until that happens, the Allison wont let it start. (or so I am told...)

 

Continued thanks to all!

Tim

[jleamont]

Tim, does your HR have schematics on the electrical compartment doors?

Like this;

[TimWright]

Those look really informative, but no such thing on mine. I do have the factory wiring diagram but everything is so small and hard to read, and frankly it is also poorly labeled. Maybe not for an electrician, but for me, very hard to follow it.

[TimWright]

Update;

So, I gave up and called the mobile RV repair folks. (Incidentally, I called 5 different companies and only one even returned my call. I guess they have all the business they need. Good thing because I won't be taking my coach to any of them for future maintenance or repairs. But I digress...)

Anyway, told the tech everything I had done, what I thought and so forth. He checked a lot of circuits, connectors, relays, and so forth. Then, he plugged in a new keypad for the Allison and like magic, everything worked! Everything! If I had not been there to witness it, I would have thought they were just trying to sell me a keypad. But, I was there. 

He had no explanation for why the other items were suddenly working as well because they should not have anything to do with the transmission keypad. But, it starts, runs, everything works, so for now. all is well. But I am keeping a wary eye for further electrical gremlins, or the recurrence of these. 

And, just for anyone who cares to know, keypad (new in the box, Allison unit) was $1000 and with the service call, labor, tax, etc, total bill was right at $1,600.

 

Thanks

Tim

[manholt]

Tim.

Great news.  Glad your rolling again!  Was the Mobile Tech from a major company or just a local?

Carl

[hermanmullins]

Friend had the same problem with his board. He found a tech in Lewisville, Texas that rebuilt his board for just a bit over $100.00. Same as you, plugged it in and walla, everything began to function. Just wish I could find someone to do the same for my Gerard Awning board.

Herman

[jleamont]

Yea, those touch pads are salty..Glad you are all fixed up!

[abyrd]

Glad you are fixed.  Thanks for the info.

 

Jim