This is listed as "in-line diode rectifier assembly", which connects through a 6-amp line fuse to terminal #14, which has something to do with the headlights/dimmer.
The part is burned out and the 6-amp fuse is blown. Headlights still function.
Anyone know specifically what this is? Maybe someone can help me figure out the value of the part?
Luke has nothing on this. Only marking on the outer vinyl cover is 'Jayco 101'(https://uploads.tapatalk-cdn.com/20180402/f0c6e1eae3b2290ff6ddbf94ce98ef9d.jpg)
it is probably for the dash lights so you can dim them if you want
dave
Richard: Take the cover off from it and see if you can read any numbers on it so it can be identified. Gerry H
So now I've gone and voided my warranty by cutting it open.. M
This was inside a cardboard tube inside the vinyl cover.
Still no markings.(https://uploads.tapatalk-cdn.com/20180402/4682a0d54bc6d07209c745f86523347c.jpg)
Back to the religious writings?
Where is it in the schematic?
Happy coaching!
Buswarrior
Quote from: buswarrior on April 02, 2018, 05:10:12 PM
Back to the religious writings?
Where is it in the schematic?
Happy coaching!
Buswarrior
I've looked at all the various pages in the wiring diagram book that discuss this, and none of them seem to give a clear picture of what it does. I'll try and summarize the various possibilities tomorrow when I'm more clear-headed. It is listed in the parts book as: RECTIFIER-Head lamp low beam. Since my low beam lights work even with this burned out, I'm not really sure how the name of the part fits.
The wiring diagrams for this coach include three variations: Standard, RPO, and SEO. The last two are for various option packages which were available from the factory. I know that I have equipment beyond the Standard, but neither of the other two options seem to fit for all the various systems. Since our coach was ordered directly from GMC by a charter bus company specifically to be converted by Custom Coach, and because I know of at least a few non-standard options that were ordered, I'm wondering if our coach doesn't fit any of the wiring diagrams directly.
Keep in mind that in all this I'm speaking specifically about the bus portion of the vehicle, which is still largely intact and not altered from how it left the factory. Custom Coach did a good job of keeping their wiring separate and distinct from what came with the bus. They also included a separate book of wiring diagrams for the house systems (which I'm updating as I make changes.)
That looks like a diode. A rectifier works off a magnetic coil and turns AC volts into DC volts, and if the rectifier is also a regulator, it keeps the battery from overcharging. The diode is there so you don't get voltage feedback.
I have no idea how this information fits into your headlights.
Like an Electrical check valve.
Electrical check valve almost makes sense. I'm not positive, but it looks like one end of this rectifier/diode goes to the same terminal where the electric speedometer gets its signal from the bus alternator. Could be there to prevent a feedback loop and a false speed reading.
Let's try that again...
I just re-read the manual section which talks about the speedometer. "A permanent magnet AC generator (sending unit) is mounted on the transmission...Generator supplies a signal...This signal is rectified to direct current (DC), smoothed and fed to meter movement of speedometer..."
Maybe this piece being blown would explain why my speedometer is inaccurate. The faster I go the more inaccurate it is.
Two questions now...
1) Why did this blow in the first place, and
2) What was the size/value of the part?
I'd like to replace it but the specific one I need is not available. My bus needs a part with the two pigtail leads as shown in the photo. Luke says it's no longer available. If I had the specs on the part it's likely I could get something to do the job. The other option is that the equivalent part for the 4905 is available (possibly), but the 4905 uses screw posts for its terminals and not the push-on connectors like the 4108a. The part for the 4905 could most likely be adapted to work physically, but I still won't know if the electrical specs are the same.
Any thoughts or suggestions? So far you all have helped me screw my head on and find some good information. Now that I'm this close I'd like to figure out the rest.
If its a diode, check it with a vometer. should show continuity one direction and no continuity in the other direction. If it is truly bad, try getting a generic diode with a good reverse current rating. They are cheap. show your pictures to an old tv repairman that worked on the old tube type tvs. He can help.
Quote from: chessie4905 on April 03, 2018, 05:34:52 AM
If its a diode, check it with a vometer. should show continuity one direction and no continuity in the other direction. If it is truly bad, try getting a generic diode with a good reverse current rating. They are cheap. show your pictures to an old tv repairman that worked on the old tube type tvs. He can help.
Otherwise, do you have a real electronics store nearby? (No, not a Radio Shack!) The folk there should know what your mystery widget is. However, one single diode won't make smooth DC from AC - it will make chopped-up intermittent DC, probably not what a speedometer needs. If you know the make and model of your speedometer, is there still anything online about it? Or just buy a new speedometer - I'm gradually replacing some of my original Teleflex gauges with new Speedhut ones that are much better.
John
No point checking this one. The burn mark indicates it got pretty darn hot. I've got one coming from Luke, although it's the one intended for the 4905 and not the 4108. I'll do what I can to adapt it to the push-on connectors.
Surprisingly, the speedo works. Not terribly accurate once above 45 mph, but it works. If this doesn't make any difference, I'll probably just go with the Speed Hut GPS speedo like I did on the 4106. Not an urgent need since I have the Garmin in front of me, but eventually I'd like to have the speedo be more accurate. I just called Speed Hut, and apparently it's possible to order one with the odometer set to the reading on the speedo being replaced, so that the new speedo will show actual miles. Since ours only has 41,000 actual miles I kind of want to keep that.
Richard: That's a big diode. band denotes cathode - if there are no markings, I would expect a 1Nxxxx number somewhere on it. If not, reverse logic, 6 amp fuse is suppose to protect it, so it should be more than 6 amps with some headroom. Fuse should blow before the diode to protect it. Possible it's a zener (voltage regulator) type. More info needed. Do you know what voltage feeds it? AC or DC 12V or 24? Whatever still works is probably not a part of the diode circuit. Something is gonna be dead because of it. Gerry H
Quote from: Gerry H on April 03, 2018, 01:23:51 PM
Richard: That's a big diode. band denotes cathode - if there are no markings, I would expect a 1Nxxxx number somewhere on it. If not, reverse logic, 6 amp fuse is suppose to protect it, so it should be more than 6 amps with some headroom. Fuse should blow before the diode to protect it. Possible it's a zener (voltage regulator) type. More info needed. Do you know what voltage feeds it? AC or DC 12V or 24? Whatever still works is probably not a part of the diode circuit. Something is gonna be dead because of it. Gerry H
Wish I had answers to your questions - it would make this much easier.
Best I can tell, the part has something to do with the AC signal coming from the signal generator mounted on the transmission. If this is the case, the signal is headed to the speedo. Speedo still works, so I'm not exactly sure what the purpose was. Guess is that it has something to do with the following found in the manual, "...This signal is rectified to direct current (DC), smoothed and fed to meter movement of speedometer..." Maybe the lack of this part is why my speedo is not accurate.
It and the fuse were dead. Not sure the exact voltage of the signal coming through. I'd have to rig up a multimeter to work while driving to try and get a read on the signal since it won't generate until the transmission is in motion. I doubt that the voltage is all that high.
I've got one coming to me from Luke that shows a similar purpose, even though the part number and mounting style are not the same. I'm hoping that I can make it work. I'm not really stressed over this, but the mystery does confound me.
Back to the religious scribings?
Headlights, speedometer...
Third time's the charm?
Happy coaching?
Buswarior
Quote from: buswarrior on April 03, 2018, 04:24:52 PM
Back to the religious scribings?
Headlights, speedometer...
Third time's the charm?
Happy coaching?
Buswarior
I take it that you don't agree with any of the current theories on this. I wish I had more information, but after looking at the manual, supplement, and wiring diagrams I still don't have a clear picture. The only description of a rectifier is in connection with the speedo, and since it goes to the same terminal as the speedo I'm leaning that way. The headlight part is due to the fact that the other end of the rectifier connects (through a 6-amp fuse) to the terminal where the dimmer lo switch connects. It's also listed in the parts book as a headlight rectifier.
Bottom line - I don't know but hope to find out.
Richard: As long as we are taking guesses, I don't think it has to do with the speedo. To rectify a pulse, typically uses a signal diode (small in nature). The one you show, is a power diode, more likely to be the headlight low beams (I know you said they still work, but maybe they don't dim anymore with fuse blown. Check that function out. That sounds more likely, that it's a zener diode and pulls down the voltage when switched on to dim the lights. Thanks for additional info, you'll figure this out, just takes time. Gerry H
Quote from: Gerry H on April 04, 2018, 03:09:45 AM
...but maybe they don't dim anymore with fuse blown. Check that function out. That sounds more likely, that it's a zener diode and pulls down the voltage when switched on to dim the lights. ... Gerry H
Not sure exactly how the function of the headlights on the old coaches should be, but I've got quad headlight. When the high-beam indicator is on all four bulbs burn brightly. When the high-beam indicator is off, just two burn.
Should there be something else going on to further dim the two that are left? Seems odd that if this was supplying power to the headlights in any way they'd have only a 6-amp fuse, but then again lots of things done on the old coaches seems odd.
I think youll find that it just draws off that circuit source.
Richard: thanks for clarifying the operation of your lights (bright/dim) I now am at a loss, cause it doesn't seem like this one is connected to your light system either. Are you certain that nothing else is not operating (dead) there should be something not working. You also said that you have one on order that may not be the same, if you install it, be sure to identify the cathode (-) band and install the same as the old one. Cathode on yellow wire as your picture shows.
Facts: 12 volt headlights typically draw about 2 amps each. Yellow wire color code usually denotes 12 volts DC. A silicon diode only drops .7 volts across it. They are sometimes used across a coil, which when current stops flowing through the coil, a high reverse polarity voltage spike is generated, the rectifier safely dumps the voltage spike to ground. Rectifiers are measured in values of current thru it (amps) a reverse voltage that it can safely handle across it, and power rating in watts (volts X amps). Food for thought. Gerry H
Richard5933
Do you have the wiring diagrams on a CD or can they be copied? I have all the books but no wiring diagrams. I would pay you for copying them.
Quote from: Bill Gerrie on April 05, 2018, 06:26:34 AM
Richard5933
Do you have the wiring diagrams on a CD or can they be copied? I have all the books but no wiring diagrams. I would pay you for copying them.
I do have the wiring diagram book, but haven't digitized it yet. Let me see if I can figure out a way to get it on my scanner in the next few days.
Maybe these will help for now... (https://uploads.tapatalk-cdn.com/20180405/3515a8ed625679959131c42d76f2ed9e.jpg)(https://uploads.tapatalk-cdn.com/20180405/683afb7d18563ed7f64487bf180264f1.jpg)
I've looked at yours and my wiring diagrams. You have some numbered diagrams that arent in my pack, (x7461). But it looks to me that that circuit is for headlamp low beams to come on when coach is running. That's why connection to generator. It looks like they happen to pull voltage for speedometer head from #42, and that connection has a 4 amp fuse in line for it. The fluctuation of speedometer could be bad condenser at connection 17, probably in engine apparatus panel. If it is a metal can type with pigtail, quite common back then for many uses, particularly in points and condensers in cars. They have a habbit of drawing moisture over time. Cheap, so no biggie to replace.
Just noticed this... Looks like I'm supposed to have daytime running lights. Who knew?
Maybe this is what the mystery part does.
The one I got from Luke isn't going to work. I found a generic diode with a 15 amp rating. Since this circuit has a 6 amp fuse, I'm hoping it will work.
We'll see. Long as we keep the smoke inside the part all is good. (https://uploads.tapatalk-cdn.com/20180406/2fde7f7e1f02f342f557c8842a4ccb0f.jpg)
No matter the problem...
A return to the religious writings, finding interpreters for those writings...
Salvation may be found!
And it works for life too, apparently...
Well found!
happy coaching!
buswarrior
This one or similiar that will handle the current from two low beams will do the job. Wire it in so band is at same end as old one.
https://www.ebay.com/itm/100x-R-6-1000V-10A-Axial-Rectifier-Diode-High-Surge-Current-Capacity-Low-leakage/131993420782?hash=item1ebb6bc3ee:g:XWgAAOSwlptaRlTi (https://www.ebay.com/itm/100x-R-6-1000V-10A-Axial-Rectifier-Diode-High-Surge-Current-Capacity-Low-leakage/131993420782?hash=item1ebb6bc3ee:g:XWgAAOSwlptaRlTi)
I found some rated at 15 amps at 45v which were designed for solar array building. I think this will work - guess we'll find out soon. Still not sure exactly what this is doing...I'm guessing that it's cutting the voltage to the low beams to make them shine at half brightness.
Got a replacement for the diode/rectifier - I found one with a big enough capacity to give it a go.
Got everything hooked up and installed. Still don't see anything different. The headlights don't light on dim (DRL) and nothing else seemed to function that didn't before. Thought maybe I had the thing in backwards so I turned it around. Still nothing.
For now I've pulled the fuse out and will have to research more to figure out what's going on. Perhaps whatever the original part was connected to it that caused it to burn out has stopped functioning as well. If I knew what it was I'd take a look.
Thoughts?
Looking this I think they were pulling half voltage off the Y connection of the alternator to power the low beams any time the engine was running and the lights weren't switched on. The diode was in the circuit to prevent backfeeding the alternator when the lights switched on. The Y connection would supply half the alternator's output voltage and it would be unrectified that is AC but the head lights don't care if it is AC or DC current. If you want to use this system, I would start at the alternator and check for the Y connection and trace the voltage forward and make sure you have the correct headlight switch. Good Luck.
Quote from: Lee Bradley on April 12, 2018, 10:46:19 PM
Looking this I think they were pulling half voltage off the Y connection of the alternator to power the low beams any time the engine was running and the lights weren't switched on. The diode was in the circuit to prevent backfeeding the alternator when the lights switched on. The Y connection would supply half the alternator's output voltage and it would be unrectified that is AC but the head lights don't care if it is AC or DC current. If you want to use this system, I would start at the alternator and check for the Y connection and trace the voltage forward and make sure you have the correct headlight switch. Good Luck.
Thanks - that's a good place to start. Once I have the energy to dig into this again that's where I'll start.
Quote from: Lee Bradley on April 12, 2018, 10:46:19 PMLooking this I think they were pulling half voltage off the Y connection of the alternator to power the low beams any time the engine was running and the lights weren't switched on. The diode was in the circuit to prevent backfeeding the alternator when the lights switched on. The Y connection would supply half the alternator's output voltage and it would be unrectified that is AC but the head lights don't care if it is AC or DC current. If you want to use this system, I would start at the alternator and check for the Y connection and trace the voltage forward and make sure you have the correct headlight switch. Good Luck.
This makes sense to me. DRLs will last much longer (or a regular filament used as a DRL when the headlights are not switched on) if they're run at reduced power -- and also the light is a better marker with lower glare that way, for the same reason, low beams are good to use as a DRL. At Land Rover, back in the '80s before DRLs got to be ubitquitous, for the N. American market we used a MOSFET clipper power reducer box with built-in backfeed protection and internal switching from the regular light switch. Our solution was very similar to what Lee is describing -- it also means that you can't see the diode actively "doing anything" but if it's not there, under some conditions of lights on and dimmer switch in the wrong position, you could get backfeed. That backfeed could mean the taillights might come on at lower intensity when you don't want them to, it could blow fuses, or give you odd sh*t like a trailer connector box burning out. The fact that the diode doesn't seem to be doing anything could be the perfect reason that it's there and doing its job and all is well.
my day time running lights turn on when the parking brake is released to move the coach
Dave
check the wire colors and verify connections at each end. If that checks out, I'd disconnect each end of that wire and verify continuity with an ohm meter and temp looong leads. Check without or before diode, then check with diode in circuit. Diode should prevent current from headlight switch feeding back to R terminal on alternator.
Quote from: Oonrahnjay on April 13, 2018, 04:50:07 AM
... The fact that the diode doesn't seem to be doing anything could be the perfect reason that it's there and doing its job and all is well.
When I said it doesn't appear to be doing anything I mean that the headlights don't turn on in DRL mode. However, after reading other comments, maybe they are designed to only turn on when the parking brake is released like in the MCI. I'll have to give that a try, as I only tried things with it sitting and running, not in moving mode. I'll chock the wheels and release the brake and see what happens.
Finally got this figured out. The rectifier is in a circuit that takes 12v from the generator relay and provides 1/2 normal voltage to the headlight low beams for daytime running lights. The reason for the rectifier is to prevent the normal headlight circuit from back feeding 24v to the generator relay when the headlight switch is turned on.
Once I realized that the 6-amp fuse I found blown in the fuse holder should have been a 9-amp fuse I was able to get things working.
All that said, the fuse does get quite warm when the DRLs are on. Not sure if this is normal or indicative of a problem downstream so I've pulled the fuse for now. My suspicion is that the sealed headlights have been replaced at some point to a newer style bulb with a higher current draw than the original. If this is so, it might explain why the original rectifier was burned out.
Since the half-voltage DRLs really don't shine bright enough to be seen in daylight, I'm not sure that this is really worth pursuing further. At least I have an answer to the mystery though.
On to solving my other electrical ghost in my start switch circuit.