So I'm getting ready for a test run with my new turbo boost sensor, cleaned bypass valve and new hoses, new intake and filter and new exhaust. Tried to start the coach from the drivers seat. Master switch on I can hear the clunk of the relay and headlights and dash lights turn on, but starter button doesn't do anything and all my dash gauges are flat lined. No power to them. Can someone point me in a direction and I'll hunt away. I can start coach from rear start box in engine bay but this needs to be fixed so I can watch gauges.
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Probably a short blowing a circuit breaker or fuse.
neutral switch...related ?
Put rear start switch back to Front Start?
Scott headed down in a few and email me your contact info (were you folks are lurking) . Will drop by and meet up. If you ever get over to SS mine is the only bus in back for a look. Hope you get the problem solved. That what makes this fun, all the fires to put out to drive them.
Glen I just private messaged you my phone number. It's my cell. I'll be around all day...
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Don I don't think so. It is intermittent, and my rear start switch is in the "front start" position. All gauges are flat. Ignition turns on fine, trans touch pad lights up and all gears work. So it has power. I'm going to have to chase this down
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Since the last place you worked was in your engine compartment I would guess you dislodged a major connector that feeds the driver's area.
--Geoff
I didn't touch wires back there. Just replaced muffler intake and turbo boost sensor. Coach still starts and drives fine if starting from rear box. Just no gauges up front and start switch on dash is dead
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My electrical manual was accidentally left behind at my in laws house in Michigan.. anyone have a PDF source for 1992 MCI 102C3
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Scott since it is intermittent I would be looking at a relay or main circuit breaker up front, or more likely a ground. If your bus is like my D series which I think is probably similar, the dash connects to the main harness through a set of big plugs. You might check there. Pull the dash and see if anything changes while moving the harnesses around.
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I can send you a pdf of the front junction box schematic if you want. Might help with troubleshooting. Let me know.
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There is a ignition relay in the rear panel check it
Quote from: luvrbus on May 25, 2017, 08:54:54 AM
There is a ignition relay in the rear panel check it
Would that cause loss of guages too?
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Scott according to the master elec schematic there is a ground stud and a 24v stud behind the dash that the guages connect to. Might be a dirty/loose connection. I will look further and see if/where the start switch is connected to the loop.
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With master switch on you should have 24v on stud 14. From there it goes to start switch then back to stud 3 if you have anti-theft then to stud 4 (straight to stud 4 if no anti-theft) from the start switch. With the start switch held in you should have 24v on stud 4. The only place the start button and guages have in common is stud 14, which gets it's power from the master relay in the front junction box.
If you find no power on stud 14 look for a 30a circuit breaker on the main 24v bus bar, position 4.
Hope this helps narrow it down. I think I would start by looking at stud 14 for power if it were me.
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Much thanks. So, I have no idea what fixed it....but it's working again. Incidentally, for a while now I've heard a relay clicking on and off in the front JBOX. I narrowed it down to the relay for the bulb test switch. Somehow this switch is also tied into my atec touchpad so with it having issues my atec pad wasn't lighting up. To get the bus going I had to bypass the bulb test switch and connect the atec touchpad directly to power. Working perfect now, relay is disconnected so I have no test lights but whatever. Half of them have never worked anyway.
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Quote from: Scott & Heather on May 25, 2017, 11:30:46 AM
Much thanks. So, I have no idea what fixed it....but it's working again. Incidentally, for a while now I've heard a relay clicking on and off in the front JBOX. I narrowed it down to the relay for the bulb test switch. Somehow this switch is also tied into my atec touchpad so with it having issues my atec pad wasn't lighting up. To get the bus going I had to bypass the bulb test switch and connect the atec touchpad directly to power. Working perfect now, relay is disconnected so I have no test lights but whatever. Half of them have never worked anyway.
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Is it a relay or a self-resetting circuit breaker that's clicking? A while ago I inadvertently misconnected something in my junction box, and I heard a CB there clicking off and on - it puzzled me until I realized what I had done!
John
Yes John, thanks for the correction it was indeed the self resetting CB. I am not sure why it was doing that but the test switch had loose wires and I'm guessing something was shorting
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I have a 102C3, and I've had this happen before
Look at the ground studs in the front electrical box on the bottom of the box. I had a stud that was corroded almost off and it would cause these odd intermittent electrical issues. I would loose things like the starter switch, electrical gauges, turn signals and it was kinda random.
Larry
MCI 102C3
Thanks Larry. I got the start switch working again but gauges are all still dead. Without a schematic, I'm shooting in the dark.
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Quote from: Scott & Heather on May 25, 2017, 11:30:46 AM
... I've heard a relay clicking on and off in the front JBOX. I narrowed it down to the relay for the bulb test switch. Somehow this switch is also tied into my atec touchpad so with it having issues my atec pad wasn't lighting up. To get the bus going I had to bypass the bulb test switch and connect the atec touchpad directly to power.
As I said. You have a short that is blowing a circuit breaker. Find the short.
BTW, when you have a short that is blowing a circuit breaker, it's generally not a good idea to bypass the circuit breaker.
Craig, the short was in a different part of the circuit. I had to remove the wires going to the circuit breaker. I then merely connected my touchpad to power. Not sure where the short is in the bulb test circuit but I can't chase this down without my schematic manual. I'll be headed back to Michigan in three weeks and will get it and troubleshoot more then.
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Ok guys, I am banging my head on this dead gauge issue. Even my fuel gauge is dead. Again, my coach electrical schematic is in my storage trailer in Michigan, but I really would like to get my gauges back online before the trek from Texas to Michigan. My jbox panel diagram indicates "AA" for dash panel gauges. I can't find "AA" on the diagram anywhere. If someone here could post and wiring schematic for a 102C3 you would make my month. Seriously. Or find "AA" on this diagram. I can't see it anywhere. (https://uploads.tapatalk-cdn.com/20170528/a3c388461e175ccca5eaf1b06ad59373.jpg)
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It would seem that the common power to the gauges is at fault. Could you use a tone generator at the gauges and trace it back to the panel?
That's exactly what I'm going to try to do right now. Thanks. It seems like WH 36 wire might be at fault but i have no idea where it goes.
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Well, looks like it might be circuit breaker #3. 6A. You're diagram above indicate AA, but I don't even see that on the diagram. I suspect it's the upper right one next to the stud board which is labeled CC. Note that the one below it is also labeled CC.
The bus bar appears to be fed through stud 14. Comes through the 6A CB and goes to stud 26. This then feeds a common point for all gauges and TT lights, though that common point location is not shown. Feed from stud 26 wire number might be 3-RD-18.
Scott just a thought, but you were working in the engine compartment when all this started.
I would go back and double check ANY wires/plugs that go from the engine/transmission to the coach. Especially any that go to the electrical panel over the muffler where you removed the old air cleaner. You may have accidentally bumped one of the plugs or harnesses and not even realized it.
If it were me I'd actually disconnect each plug and spray them with some CRC electrical cleaner (or equivalent) and then put some dielectrical grease in them before reconnecting them.
Might not be the problem now, but good preventive maintenance that should be done periodically anyway!
;D BK ;D
Thanks Craig....I'll use your numbers and continue chasing...
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Bryce, my fuel gauge is dead too...which tells me it's not in the engine compartment??? I have been unplugging every harness behind the dash and cleaning it and plugging it back in. I have two cans of CRC so I'm going crazy lol. The only thing I've messed with really is the stud that feeds the bulb test light. But nothing there seems to be connected to the gauge power as far as I can tell....if I had my manual with schematic I could methodically chase this down. I might end up just driving without volt and fuel gauges. My coolant temp gauge works fine. This is just weird
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So which gauges work and which ones don't?
Coolant temp works
Speedo works
Air pressure works
Voltmeter dead
Fuel gauge dead
Oil pressure dead
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Double check and clean up all the grounds. That is where the problem lies more often than not.
JC
Quote from: Scott & Heather on May 28, 2017, 11:03:04 AM
Coolant temp works
Speedo works
Air pressure works
Voltmeter dead
Fuel gauge dead
Oil pressure dead
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I don't see Air Pressure, Voltmeter, or Fuel in the schematic. The oil pressure is in with the speedo and water temp. I was thinking maybe the others were aftermarket and connected differently, but the oil pressure is killing that theory. Also, both water temp and oil pressure come from the back. Both are attached to an engine block terminal, and both go through a harness connector on the engine side of the rear junction panel. So, potentially there might be a problem in that harness connector, especially if you did recent work in the engine compartment.
Since oil pressure is shown in the schematic I have, I suggest you start with that. From the oil pressure sensor, a wire goes to pin 3 on the block terminal strip. Then it goes to "Pin C" on a harness plug, and continues to stud 34 in the rear junction box. It then goes to stud 1 in the front junction box. It then goes through a connected, probably under the dash and to the gauge. There are 3 terminals on the gauge, ground, 24V, and sense wire described above.
So maybe start there and see if you can find a disconnect in that circuit.
You have a TYPO I think.
If you look just to the left of stud 13, CB says "CC". Directly under that is another CB "CC". I would bet the one following "Z" might be the issue?
Awesome Craig. I checked everything in the front jbox from the gauges to the studs. Solid connections there. I used a tone generator initially then read the wire labels. So we are good there. Gauges are grounded properly. I'll check the rear jbox and harness. I did zip tie that harness to get it out of the way. It was hanging down. I had no idea my fuel gauge went through that way back there. Thanks so so much Craig for your help. Andrea not a typo that I know of. Two different amperage breakers both involved with the "check bulb" test button circuitry.
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I would be surprised if the fuel gauge goes through the rear panel, but I don't see it on the schematic.
Are you sure you have 24v to the gauges that are not working?
I'm confused at this point. A black wire labeled #3 is connected to a stud on each gauge (all three, volts, fuel, oil). I assumed that was the 24v feed. But there isn't 24v going to them at all after checking with my voltmeter. The other stud is sensor, and the other one of curse is ground. I applied 24 volts to the power stud and it did nothing but heat up my jumper wire which I immediately removed. I'm at a loss here. I need to just take some time to look hard at this with my schematic. Thanks so much for trying Craig. at least I know I'm good at the back up to the front. Somewhere in the front, we've lost 24v to the gauges. I'm not sure where the 24v feed for them comes from but that's likely my issue.
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I am a bit vague on what's going on, but since you say that jumping 24v just heated up the wire, would that suggest a short?
Start with volt meter when the main switch is on both studs should be hot they tie a lot of gauges into the Volt meter loop
If it heated up when you touch it with 24volts might be the ground not the power stud. You created a short. Touch the ground probe to the bus body or metal and then touch the positive probe to each stud with key on and see if you have 24 volts on any of the three. Just an idea from a distance. Like Clifford said it may be wired in series to all 24 volt gauges or a few in a row.
Quote from: Scott & Heather on May 29, 2017, 02:21:36 PM
I'm confused at this point. A black wire labeled #3 is connected to a stud on each gauge (all three, volts, fuel, oil). I assumed that was the 24v feed. But there isn't 24v going to them at all after checking with my voltmeter. The other stud is sensor, and the other one of curse is ground. I applied 24 volts to the power stud and it did nothing but heat up my jumper wire which I immediately removed. I'm at a loss here. I need to just take some time to look hard at this with my schematic. Thanks so much for trying Craig. at least I know I'm good at the back up to the front. Somewhere in the front, we've lost 24v to the gauges. I'm not sure where the 24v feed for them comes from but that's likely my issue.
Again, you have a short somewhere that's blowing a circuit breaker.
Wire 3 comes from the master control relay, which is enabled when you turn on the master switch. It goes to stud 14. Check stud 14 for 24v. From there, it goes to the 6 amp circuit breaker #3. It's probably the one labled CC in your above diagram, but I think it's mislabeled. I can't read the amperage as it appears to be torn there. It's the one next to stud 13 on the stud panel.
See my other post for routing to the power stud and gauges. I think your short has blown the 6A circuit breaker. You'll need to disconnect each of the gauges one at a time, as well as the tell tale lights connected to that feeder until you find the short.
BTW, this circuit also feeds the trailing axle unload, so it does go to the back, so the problem could still be back there. These connections are in FJB stud 28, so you might want to start there. It also feeds the buzzer alarm.
I wonder how many wiring schematics MCI had for DDEC equipped buses I don't know how it runs with the check engine light out of the loop and the DDEC is reading oil pressure or it would not run.Gauges are usually easy to trouble shoot with Ohms meter
Nothing cliff. Nada. Dead. No voltage. I need to find out where the 24v is supplied for the gauges. Craig just helped me out bigtime by sending me the electrical manual! Wish me luck team :)
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Page 177. Look for FJB stud 14 on the left side of the drawing about half way down from the top, and about 1/4 of the way in from the left. You need to find that 6A circuit breaker that is to the left of stud 14. That's circuit 3 which feeds the gauges.
THANK YOU CRAIG! Sure enough, that breaker was self resetting so I removed all the wires to it to stop it. According to the diagram it was just supposed to feed the test bulb system but apparently it also feeds the gauges. Back in business. Thank you again. You made my month!
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Quote from: Scott & Heather on May 30, 2017, 08:32:55 AM
THANK YOU CRAIG! Sure enough, that breaker was self resetting so I removed all the wires to it to stop it. According to the diagram it was just supposed to feed the test bulb system but apparently it also feeds the gauges. Back in business. Thank you again. You made my month!
Did you find the short? Breakers don't typically trip for no reason. They trip because of an overcurrent situation. They may then reset after they cool down, but if the overcurrent situation is not cleared, the breaker will simply trip again.
What diagram are you talking about regarding feeding only the test bulb system? I don't see a test bulb system on the schematic.
That particular breaker is labeled "test bulb switch" on my front jbox diagram. "CC". I have a short in that test switch and it's been previously soldered so many times and goobered up that I just thought I'd disconnect it for now at that breaker. I know the short is in there. Problem is I also inadvertently killed my gauges. I hooked everything back up, but disconnected the switch and all is well. No breaker tripping. I'll have to re-wire the bulb test switch someday but for now it's low on my priority list. My bulb idiot lights are also majorly soldered and goobered up. I'll have to spend some serious time getting those working properly again.
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I'm glad you found it. I was wondering why there were two "CC" breakers.
Craig is awesome! He's helped me understand so much ;D