Erratic Gauge Readings

I have a 99 Country Coach, 98 Prevost XL, and begun to get erratic gauge readingstoday. The 24 volts would go down to 20Vfor a while and bounce around before returning to normal and doing the sameagain. The front and rear air pressuregauges would read normal and occasionally bounce to zero for a few secondsbefore returning to normal.

I checked the 24V at the battery jumper connections and thevoltage was as expected at just above 27V. So, I’m confident the problem is most likely a poor connection in thecommunications bus to the gauges. BTW, Ihave a Country Coach with a glass display. I doubt it’s the computer that drives the display given all other gaugesperform normally.

Any thoughts on which connectors to start with? Any thoughts on my logic being flawed? I’m in Minot, ND so getting commercial helpis not going to happen here. They have a Detroit Diesel shop, but it doesn’t doservice; they only sell parts.

Thanks,
Gil

The first thing I would suspect would be an intermittent ground, especially if the gauges drop at the same time. I am not that familiar with the CC systems, and am sure one of the CC owners will chime in with a solution. It is just a thought. Hope you get it figured out quickly.

Gil, Assuming you have already done a dash reset I would check the ribbon connector in the computer cabinet. If you don't find the connector behind the locked door remove the top of the ledge behind the drivers seat. It is held on by velcro so it just lifts up. I believe there is a diagnostic procedure if the odometer and hours window turns a different color when the erratic readings occur. This specific issue tends to go in the direction of the computer. All other issues are usually a ground or connection problem.

Jim,

Actually I didn't try a reset given the computer did come up. I thought the reset was really Windows boot reset. I did remove and replace the ribobbon cable and every other cable I could find. I'm still trying to find where the 24V is monitored for the voltage display. You don't happen to have the wiring diagrams for the computer and related sensors do you? Is there a procedure for using the reset or is it just a push when ready operation?

Thanks,

Nothing special about the reset. Just open the guard flap and push. I think you are correct, it is just a re-boot for the computer. I will look for more information.

Gil, According to my schematic wire # 30 ppl is for the Main Air Tank and # 31 brn is the Aux Air Tank. Wire # 391 ppl is the 24 volt constant v+ from the chassis batteries to ECC for chassis battery monitor, and to GSD circuit board in the overhead cabinet.

Jim, great information. What is the GSD board and where is it? I know the air pressure device that changes from air pressure to an electrical signal is in the steering box door.

Gil, I called Country Coach to find the location of this board for you. And this is where it starts to not make sense. GSD stands for Generator Shut Down Board. It is supposed to be in the cabinet above the drivers seat. Armed with this information I don't understand how this board could play a part in your false readings. Then again I am continually surprised by what I learn about our Bus. As you probably know Country Coach is back in business and some of the old employees that were there when they built our Buses are back to work. If you call them you need patience because they are not overstaffed. Greg in Technical Support is a good contact. If he does not know the answer he will find out by talking to the right person and call you back. 541 234 2167. Also, take a look at them on the Internet.

How is your trip going ? Will you be in the area of Country Coach ? Might be able to get a lot of questions answered. Wish I could make it a destination someday.

Thanks Jim! I sent CC an email and they are trying to run down what drawings they may have. I have several wiring diagrams, but nothing on the communications links to the computer!

Thanks again for reaching out to CC. BTW, do you know how to test the automatic generator start to see if it really works? On the system I had before from Magnum Energy, there was a test button as well as a display to let you know it was actually monitoring the voltage. The best I can tell the system we have is based on "trust us" it will work when needed.

Gil, You may want to check with Miles C. if you don't receive quick help from CC. Jim may know if Miles has these particular drawings. Miles is the best I know at troubleshooting schematics. I haven't heard of anone having this problem.

Dale's post reminded me of a sheet of information Miles found when he was gathering information from Country Coach at Country Coach. It is titled " Trouble Shooting Digital Dash. " Looks like it was written by in house Techs. Not real comprehensive but it includes more information than most of us know. If you give me your email address I will send it to you.

There is no way to test the Generators Auto Start. The Gen Com Board is in the Generator Bay accessed from the second bay back on the passenger side. The original setting started the generator at the voltage drop specified by Country Coach. I thought it allowed voltage to get to low and I sent mine in to Gen Com and had them raise the start up voltage point level.

Tell us how your trip is going and if you have made it to your destination.

Jim,

Nick sent me some data yesterday that may have included the same troubleshooting aid. The aid doesn't go into much detail, as you suggested. I see from the data that newer variants included a GPS, mouse, second screen and a few other items.

I did find 2 boards behind the TV that had wire 291 going to them. Yes, the 24V was on both of them. There are at least 3 boards behind the TV. Two sitting flat on the floor of the TV cabinet and interconnected with a ribbon cable. The other board is mounted in the upper left of the cabinet nearest the front cap. My bet is the two interconnected boards are for the voice response system. I'm still am not sure where the data interface board is that samples the 24V and directly feeds that to the computer over the D900/901 cable or other direct connection to the computer.

We began our trip outside Tampa. We stopped at Prevost-Jacksoville to have the bags replaced as a routine maintenance item. Then we spent a couple weeks with my daugther's family in Virginia, outside of DC. Since then we've been on a pretty fast track to Alaska to get to my sister's home in Palmer before she closes of it's sale. The weather has been hit or miss, with the first three days out of VA mostly rain. I was a bit surprised just how high the road tolls are for 5 axles through PA, OH, and IL. We anticipated some gravel roads in Alaska, but not in the US. Much to our disappointment we had a good 10 miles of gravel on US 2 through Montana. It seems they take out the existing two lanes first when they are widening the roadway from two lanes to four! Crossing the border could not have taken more than 5 minutes; that was a pleasant surprise. We got stuck here in Edmonton, which isn't a bad place to be stuck. The weather last night and early today was cold, gusts to almost 70mph, and heavy rain. I also discovered both belts of the right side A/C and alternator. One was broken, the other just sitting there. It must have occurred in the park given I didn't have any indications of an alarm. The pulley for the A/C doesn't have the right size pulley. The V's aren't wide enough to match the other 2 pulleys. I hope the belt that failed did so because it was it's time or from a rock getting into path. Anyway, belts have been replaced and I bought a set of shorter ones that will allow me to bypass the A/C unit if I have to. The only other problems I need to work on is the air compressor sometimes trips the breaker and there's a small leak somewhere above the driver's side seat. It's slight and only there when there's a big down pour.

Thanks for the update on your trip. Try to slow down and enjoy it. Don't make the same mistake I always make. I forget it is about the journey, not the destination.

Sounds like you have the same Digital Dash informaton I have so at this point I'm out. Don't think I can do much good for you. The leak above the drivers position will most likely be the marker lamp. They all need the gaskets replaced from time to time. Some removable calk over the top edge will get you by until you get new gaskets. The belt configuration for the Over The Road AC is the only downside of the system. I have found a B93 or 94 lasts longer than an X belt with the notches. I have always wondered what number belt would work if the AC Compressor or Alternator went out. I would appreciate knowing what number belt you purchased for a spare.

Sorry to hear about Harley.

Jim B85 or BP85, depending on your source, will fit if you only want to support the alternator.

We have had some 300-400 days, but generally, once we hit Canada we have slowed down. We're at Mile Marker 0 of the Alaskan Highway today.

Thanks for you comment about Harley.

Gil