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High Idle Quit
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Davy, when you shut off the engine and restarted did you also shut off the battery switches?
Kirby
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The light that indicates the parking brake is engaged does not come on as it is supposed to do. The service brake lights work fine. A fuse is worth investigating.
No, I did not shut off the batteries. I will be parked until Monday so I can do that easy enough.
Thanks for the ideas.
Davy
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Just out of curiosity, can you use the cruise control to set high idle on a Prevost like you can on a production motorhome? On our Affinity, I could turn cruise control on, get the RPMs up to high idle, then set the cruise, and it would stay at high idle. All with parking brake on in neutral, of course. I haven’t tried on ours, since I use the high idle switch, and Jeff has the coach right now. If it works on a Prevost, it is an alternative if the switch doesn’t work.
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Cutting the voltage from the batteries did not do it. Thanks for the idea though. The cruise on mine will not set the high idle. I did not think it would but I tried.
Davy
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OK, so here is what we “know”. The parking light is not on when the bus is in neutral and the parking brake is set. That seems to be the reason the High Idle will not go to High Idle.
I think I mentioned that Jeff told me how to jump the pressure switch that is triggered when the brake is set. He was hoping and I was hoping that the parking brake indicator light would illuminate and the High Idle would engage. That did not happen.
Since another requirement of High Idle is the transmission being in neutral, is it possible that a relay or something is preventing that news from traveling to the proper place? If so, what and where should I check. I have looked for blown fuses and such but a specific place to look would probably help.
Davy
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I have no expertise with relation to high idle, but it is obvious the solution is to buy a new bus.
We love spending other people’s money.
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Davy, i searched “Prevost high idle troubleshooting” on yahoo and found an old thread on pog. It was a different problem as in not inop but erratic op. They talk about the ground on a specific relay as well as a couple of other things. Don’t know if you have seen it but maybe it would help. I would post a link if I knew how.
Ps. The bus was a 96.
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Jon,
That is one solution that I had definitely not considered. Let me give a new bus some thought…uh, no! A new bus has slides and who needs slides?! Besides I have a hard time figuring interest and payments on 2++million using my abacus.
Jeff,
I did see that thread on POG when I first googled this problem. I did not think it applied to me then but since this has not been a quick fix as of yet, I will re-read it.
Thank you
Davy
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Davy,
I am just trying to keep the economy going. Tom will sell you his no slide coach because his poor suffering wife Nancy really wants slide.
A side benefit is you are helping poor Nancy.
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Your compassion for Nancy knows no bounds, Jon. There must be some kind of award for that.
Davy
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https://techpub.prevostcar.com/en/download?id=7713&type=wiring-diagrams-search-pages&mode=view
Looks like junction block 20 on the front panel should have 24V with ignition on. If your gauges work, you should have power here. Then check for 24V on one pin of the parking pressure switch. When that switch closes (park brake set), you should have 24V to junction 69 up front. If the indicator light doesn’t come on for the parking brake, your problem probably lies here. Power should also go to the high idle switch. This diagram says to see pg. 2, but it’s not there. The relay list that shows the high idle relay (R22) says pg. 3 (bottom right corner)
https://techpub.prevostcar.com/en/download?id=7711&type=wiring-diagrams-search-pages&mode=view
It comes in on 91A and out of the switch on 91B, then into pin 86 on Relay 22. It also requires that the neutral switch (connected to pin 85) is grounded on the transmission. If you can measure 24V between pin 86 and 85, and the relay doesn’t click closed, the relay is bad. If pin 85 isn’t grounded while in neutral, then you have a neutral switch problem, or an open circuit in the wiring between the relay and the neutral switch.
When it closes the relay, it appears to change the resistance, and therefore the voltage signal of the electronic throttle, forcing high idle.
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Thank you for the information. Much of it is above my pay grade but you have explained it well enough for me to have a chance to work through it. I should be in one place most of next week and I will check it out then.
Thanks again,
Davy
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NOTE: The voltages I wrote in this response proved later to be faulty do to user error. Refer to later in the thread for proper voltages.
I am reporting on a partial completion of BDuplan’s suggestions.
Junction block 20 and 69 in the front panel both have 24V with the key on. 20 has no voltage with the key off. 69 still has voltage with the key off. The bus is in neutral and the parking brake is set.
The sensors below, I believe these to be the sensors, show 24V on top with the key on and parking brake set. There is no voltage on bottom with the brake set. They both show no voltage on top or bottom with the key on and the parking brake released.
I had already jumped those sensors at Jeff’s instruction to see if I could cause the parking light to illuminate and the high idle to engage.
I did not complete the rest of the tests yet.
Do my findings show me anything of value yet?
Davy
1999 XLV X-6872, liberty #440 -
Absolutely; this narrows our search!
So power at post 96 is the furthest that you have traced it so far. And you say that your parking brake tell-tale lamp is inop. So that means that there is a problem somewhere on wire 91A, which should be coming off of post 69 in the front junction box. 91A splits and one leg goes to the tell-tale through connector C4. The other leg goes to the high idle switch through connector C155 (which I’m guessing is at the switch itself).
The next thing I would do is access the back of the switch by unscrewing the dash panel and see if you have 24V to the switch (pin 1) with the key on and with the parking brake set. If not, and post 69 still has power, we have a bad piece of wiring. Also check for 24V to the tell-tale while you’re in there. If neither has power, the loose connection is most likely between post 69 and wherever that wire splits. It’s either that or you have a problem in each of the two legs after the split. It would make sense for it to split under the dash, since the tell-tale and the switch are both there. The wire should be labeled with a sticker that says 91A.
If by some chance you do have power to the high idle switch, the next thing to check is for continuity between the switch pins (1 and 5 according to the diagram) with the switch turned on. Easiest way to do that would be to unplug it and measure resistance between pins 1 and 5 with the switch turned on. If that is OK, our attention turns to relay R22 and the transmission neutral switch.
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Thank you for taking time to walk me through each step and explain it carefully. That is a huge help to me. I will get back with results.
Davy
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