Ignition on, dash lights up, bus won't start......

Well, there I was in beautiful downtown Lake Havasu City AZ this morning, and was fixin to leave camp. Turned on the ignition key, waited for a couple of moments and hit the starter... Nothing would happen. My dash & gauges were all lit up but the starter wasn't doing a thing.

I cycled the key again and paid more attention this time. I forget exactly what the indicators say, but its like a " check engine" light or something and another one right next to it, that the Prevost book says you should wait until these lights go out before cranking... at any rate these two lights were not lighting up at all and I also noted the display on the tranny control was blank too.

Thinking that my immediate departure was going to have to hinge on someone smarter than I, I called Truk. Belive it or not, his fine wife told me he was ACTUALLY taking a shower, and she was on the other line with CNN to report this unusual behavior on his part....

So plan B was to call Joe at PV Mira Loma... And he helped solve it.

To make a long story short, I had turned on the light in the engine bay the night before, and in fumbling around in the dark to find the switch, I had bumped the remote engine start switch in the bay, off its "normal" setting.

Returning it to its regular "normal" spot instantly resulted in a happy purring series 60....

Sooooo just in case you have similar problems someday, that is the likely cause.

As I was showering away, mama truk opens the bathroom door and yells, "Jeep's on the phone and can't crank his thingee". I yelled back, "Tell him to use Viagra like he did the last time".:D

Now he gives you some lame story about the bus not running!:p

Warren: Related to the problem you described. One fairly common starter hesitations is caused by a sticky 24v solenoid located in the electrical panel below the drivers window. These solenoids get sticky at times and have to coaxed to work. Carrying a spare is suggested. I know this was not your case this time but this note may help others trouble shoot a possible problem in the future. These solenoids are not unlike the 6V one used to start my 1931 Model A Ford.

A little more on Harry's comments. There are 4 of these relays on our coach: 2 in the forward electrical panel under the driver's window and 2 in the rear electrical panel above the engine. All 4 are identical but two control all of the 12v chassis systems and 2 control the 24v systems. Failure of any will shut you down. By the way, Dale (or maybe Kevin) mentioned that most relays can be jumped in an emergency and I'm sure they can if you know what you're doing. :eek:
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94 Liberty XL

Interesting, I am carrying some 12v relays along in the parts box.. Do you need a different relay if it is being triggered by a 24v switch ?

jello_jeep;Interesting, I am carrying some 12v relays along in the parts box.. Do you need a different relay if it is being triggered by a 24v switch ?

Warren, a relay is an electrical switching devise that allows one to switch various electrical loads and voltages with a voltage of the same or different value. There are two voltages to consider with a relay the control and the controlled. The control voltage is for the coil that moves the contacts to open or close the controlled voltage contacts.

The general case would be that the voltage of the switch controlling any particular relay would also be the operating voltage of that relay. Such as 24v supply, 24v switch, 24v relay. That relay then could be switching something with a completely different voltage and amperage and it could be either AC or DC. In your case the starter would be a DC voltage at a much higher amperage, which would require a very large wire to carry the load. You would not want the large wire running the length of the bus and to a switch on the dash ( the switch would have to be excessively large) and no one would like that). Extra weight and voltage loss also. Both bad . That said it is further possible to have the switch controlling a relay that is controlling the relay you are speaking of and they both could be working at different voltages. I don't think that is the case in this application. I can not think of any reason to wire it up that way.

What you need to do is get out your volt meter and find a helper to activate the switch in question and you check the voltage at the relay. Check the coil voltage.

If you were in an emergency situation You could try the 12v relay in a 24v circuit if the terminals connected up the same. This would be a temporary fix if it worked ( the relay would probably burn out but just might last long enough for one start). To go the other way with the voltage would doubtfully work, because the 12v supply would not be adequate to cause the coil of the solenoid to actuate the contacts for the load. But again in an emergency I would try it.

As mentioned before jumping would also work if you had the right stuff!

In case this is more than you wanted to know, there might be someone else that wants to know.:confused:

Some guys are better at jumping than others.:eek: ;)

If you want more ask.:) JIM

Nice description of a relay Jim..

I am familiar with the theory and operation of them, was more or less curious if someone already knew if the control voltage in the 24v (load) relays in the Prevost setup was the same as the 12V. My bad for a too ambiguous question.

Now that I think of it, I belive the mechanic at PVML told me they were the same.

I just like to have some extra parts on board. I read earlier posts about throttle position sensors, and snagged on of those for the goody box already!!

Thanks again.. Nice informative post!!!

Just to try to reduce confusion on this relay business, consider this:

There are 4 relays on the coach that are like the "master switch" on an airplane. In the front electrical bay below the drivers side window there is a 12 volt master relay and a 24 volt master relay. In the rear engine compartment electrical box there is one of each also.

A relay labeled "12 volt engine run front" on the diagram on the door controls the 12 volt circuits attached to it. The "24 volt engine run front" controls the 24 volt circuits attached to it.

In the rear they are labeled "12 volt engine run" and 24 volt engine run".

Here is the trick:
All 4 of these relays are operated by 24 volt power!

Brian bought me two spare relays that arrived from Prevost the other day. On them it says:
TYCO
VF7 41H11-505
24VDC
Made in Portugal

According to Brian, you can buy part number 'VF7 41H11-505' in both a 12 volt and 24 volt operating voltage. We need the 24 volt for all 4 of our relays.

There is also a nifty little wiring diagram stamped right on the relay that shows clearly which pins to jump to manually operate the system. If you carry a jumper wire with two spade connectors you can wire the relay plug pins permanently ON to get you down the road temporarily.

I hope nobody ever needs to put this business into practice!

Good to know Peter. Does anyone know what the failure rate is for such parts? One or 2 in 5 years? Gary

Good post Peter. A question that comes to mind is:are the relays plug in or are the wires screwed to terminals? It would be nice if they plugged in then they could be interchanged easily in an emergency and to trouble shoot. :confused: JIM

Jim,

A picture is worth..... The wires connect to the relay terminals with spade connectors. As Peter suggested, a short wire with male spade connectors could be used to jump the wires. Needless to say the wire gauge of the jumper would need to be at least as large as the leads they are jumping. This is not an exercise for the amateur :eek: (like me) besides, the relays are cheap.
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94Liberty XL

Thanks Brian, I see everything I need to know. I was imagining a more industrial type with round pins on the end that pluged into a socket. Similar to the old radio tubes. :cool:

I agree a handfull of what you have in a cigar box on the shelf is the easiest and best insurance. It never ceases to amaze me how much trouble and grief a little piece of foreign crap like that relay can cause.

:) JIM

The relays are just plug in. These have individual wires with spade connectors attached that you push onto the relay. Some of the other relays plug into a receptacle.

I have no idea what the failure rate is. But if one out of the 4 fails, I think your engine will not run. So interchanging them would not solve a stuck on the side of the road problem.

The best thing is to carry one or two as spares, then if you suspect a problem you can substitute a relay to test your theory. Carrying a spare is much simpler and cheaper than calling a tow truck!

Petervs;The relays are just plug in. These have individual wires with spade connectors attached that you push onto the relay. Some of the other relays plug into a receptacle.

I have no idea what the failure rate is. But if one out of the 4 fails, I think your engine will not run. So interchanging them would not solve a stuck on the side of the road problem.

The best thing is to carry one or two as spares, then if you suspect a problem you can substitute a relay to test your theory. Carrying a spare is much simpler and cheaper than calling a tow truck!

Peter and Brian, after seeing the image and thinking about the situation, if all the important relays are similarly mounted I would for myself buy 4 new relays and mount them upside down on the same mounting screw on the panel board directly above the original.
Then in the shop under ideal controlled circumstances color code the relay terminals and the wires so that under what you could imagine to be the worst possible circumstances you could with nothing more than a flashlight move all the wires to the new relay very easily. :cool: JIM

Jim, no wheels for now,

Will you be hitch hiking to POG III? If so, will you work your way down to I-10? If so, tell us and we'll be on the lookout for you and blow the horn as we go by.

Naw, not really. We'd pick you up.

Lew

Here is a little history of relays.

The pictured relay is typical on later model rivet coaches and maybe XLII coaches.

Early model rivet coaches used relays that looked like a small zinc plated can with threaded posts to attach the coil and current carrying wires. These relays could be found at NAPA strores and WW Grainger to just name two sources.

What is important for all bus owners to realize is the best thing they can do for themselves is to buy some spares and keep them in the bus. For the few dollars of investment you may save some really serious dollars for a service call.

But in the event of a relay failure, if you do not have a spare relay you can temporarily get going by placing a jumper between the two load terminals. The time to get an understanding of this is when you have a coach sitting in your garage and you can play around with a tester and some wiring diagrams that you can download from the Prevost site, not when you are in a remote area of some national park.

Also, if you cannot get the coach to turn over using the key, see if you can start it from the rear. If you do that you will not have any gauges but you can get it running.

If I'm on the right page on this, a good description of that switch is a lot like (not exactly) a solonoid on an old Ford.

Lew

That's the one Lew...

I forgot to mention in the earlier post that the Bosch relays are a vast improvement over the older large relays. On our 1987 vintage coach the drivers AC fan, the lights, the start circuit, the battery isolator, and a few other things had those can type relays (I called them solenoids) and I was always replacing them because there were so many and because they just seemed prone to failure.

Well I got lucky tonight, no not that way men! I was getting the bus out ready to make a two- three day run leaving out Tues, and the bus fired up and ran for a short time, spit and sputtered a number of times and then died -couldn't figure out what was going on. I had my three year old grandson in the copilot seat, but when I fired it up and to let the air build I looked to the left out of the rear view mirror, I am talking for just a second. Turns out that my co pilot had slid over to the buttons and had flipped the alarm button to the point it disabled the engine. To say the least - I didn't know it would disable the engine, and two I didn't know the button had been flipped. So I crank it for a resonable amount of time. Get the Granny to take the kid while I try to diagnose the problem and after a while of me at the back and the front, in and out, thinking about calling A1, getting pretty torqued, I look down and start examing switches on the dash, questioning in my mind the position of all of em. Turns out the alarm switch was down and should either be in the middle or up. All is well at this time. Point is a three year old great little boy can move really fast when you ain't looking. 2 hours shot.:cool:

Roger,

I can identify with that problem. My grandson (3 years old also) was playing around in the bedroom of my '93 and he hit the ALARM button. My son-in-law is driving along and all of a sudden the horn starts blowing. On and off non stop! My son-in-law tried everything he could think of but couldn't stop the horn from blowing.

He calls me on the cell phone and asked me where the fuse was for the horn, I ask why, and he tells me the horn is blowing on & off non stop. I immediately knew what had happened and told him to walk to the bedroom and turn "off" the ALARM button next to the bed.

Problem solved: grandkids, you gotta love 'em;)

I hate when that happens:eek:

I purchased the 24 V relays at my local NAPA parts store. They suppy a lot of trucks in this area.