| Author | Message | ||
| philip potter
Rating: |
After switching engines (to a 6v92) in my MC8, my "Not Gen" light is on. I hooked the wires from the bus back onto the new alternator. The main poss line to the big "poss" post. Then there are three small post. I hooked up the small wires to the "relay" and "F1" post. I marked the relay wire with a zip strip when I removed it from the old engine so I should not have them mixed up. The new alternator has a bridge from the large "poss" post to the "F1" post. The alternator on the old engine that was taken out did not have this bridge. What is this bridge for? Why did the old one not have it? Am I missing or forgetting something simple? I wait for the air pressure to be up to normal, my air warning light and buzzer stops, but the "Not Gen" light stays on. While we're at it, please help me understand why an alternator does not charge until air pressure is built up. How does the generator know when the air pressure is built up so as to kick on? Have I missed hooking something back up? | ||
| TWODOGS (Twodogs)
Rating: N/A |
you don't say what kind of alt. ---on delco remy alt. the # 1 post is the one that's supposed to be hot when the key is on...and I think it's the one that sends the signal for the gen. light | ||
| captain ron (Captain_ron)
Rating: N/A |
I had simular problem, gen would not charge, I had to take bridge out move field wire to the field that was bridged to pos post and ground other field to gen case. | ||
| Sean Welsh (Sean)
Rating: N/A |
Philip, Many 50DN-type alternators are regulated on the ground side, meaning terminal F2 goes to the regulator, and F1 is strapped directly to battery positive. That's what the bridge wire is for. If you have a different regulator, it might be a P-type, in which case F2 should go to ground, and F1 goes to the regulator. The "Not Gen" signal is generally taken off the Relay terminal. A 12-volt relay (for 24-volt alternators) operated by the R terminal opens the ground for the Not Gen lamp. To properly answer your question, I'd need to know the model number of your regulator. -Sean | ||
| Sean Welsh (Sean)
Rating: N/A |
Oops... Missed the last part of your question. The way an alternator "knows" to "kick on" is that the regulator tells it to. The way the regulator knows that the engine is running (or supposed to be) is through a regulator terminal, usually called "Ignition" that is tied to a signal that is hot only when the master switch is in the "run" position. If the Ignition terminal on the regulator is, instead, hooked to some other place, such as the output of an air pressure switch, then you can get the behavior you describe. I'm not familiar with the MC8 regulator wiring, so I can't tell you what the OEM design was. However, if it were my bus, I would set it up so the regulator is on whenever the engine is running, irrespective of air pressure status. -Sean | ||
| philip potter
Rating: N/A |
things I don't know: 1. Type of alternator. How do I know what I have. It has 030353 7/99 NPB stamped on it. This one is direct drive. the one on my old engine was a belt drive. Someone also hand wrote on it the following 6.13.00 988270 neo4960 2.where is my regulator? the book shows that it is probably 4" x 6" or so, but I can't find where they put it. things i do know: 3 wires were hooked up to the old one and are hooked up to the new one as follows: I followed the wires back to the rear junction box and the were labeled back at the box. F1 i have to F1 post R1 i have to relay post Big poss cable is connected to big poss post. The only visable difference between the old and this new alt. is that this new one has that bridge from the main poss post to f1. I tried taking off the bridge, it still makes no difference. Please Help me understand the function of the F1 and R1 wires. Is it possible I'm charging and I'm missing something to make the light go off? any more help you can give to help this old mind of mine figure this out is greatly appreciated | ||
| Sean Welsh (Sean)
Rating: N/A |
Philip, Externally regulated alternator setups are either P-type or N-type. P-type are regulated with a positive signal, N-type with a ground signal. You need to know for sure what you had in there to put the new one in correctly. Trace the wire that you had labeled "F1" -- I'm guessing the regulator is at the other end of this wire. (Alternatively, someone here more familiar with the MC-8 can maybe tell us where the regulator is normally installed in that model.) Then give me the model number. However, I can guess, if you only previously had wires on F1, R, and POS (or BAT), that you have P-type regulation. The last part number on your replacement alternator is a Neoplan number. Neoplan uses an N-type system. In the N-type system, F1 is strapped directly to positive, and the regulator connects to F2. To use this alternator in a P-type system, you need to remove the strap between F1 and POS, and install a strap from F2 to ground. The regulator then connects to F1. All that being said, if you have a P-type regulator, and you connected it to F1, but you left the F1/POS strap in place, and you ran it that way, then you may have already fried the regulator, the alternator, or both. OTOH, if there is nothing at all connected to F2, then it is possible nothing at all happened. In which case, the alternator will certainly not be putting out any current (which is probably just as well, if the regulator is not properly connected). I *strongly* recommend you sort this out before you start the engine again, possibly doing further damage (though it may already be too late). In regards to the function of F1 and R, as I already wrote, F1 (along with F2) goes directly to the field windings. R (or R1) is a "relay" terminal, which is taken from one point on the diode bridge, meaning it is half-wave rectified DC (so will be approximately 12 volts on a 24 volt alternator when, and only when, the alternator is putting out current). It is generally used to signal that the alternator is generating, and is also often used to run dashboard tachometers. Lastly, alternators and regulators are made to go together. Depending on what alternator you had before, you may need a whole different regulator to run this new alternator. Call me on 408-892-6227 if you want to discuss this live. I am in cell coverage tonight (can call until, say, 21:30 PDT/MST) or you can call me in the morning before we head out, say between 09:30 and 11:30 PDT/MST. (We're in AZ, which is on Mountain Standard Time, which is the same as Pacific Daylight Time). -Sean | ||
| Ray Lala (Rayshound)
Rating: N/A |
Sean on an mci-8 it uses an external 24 v regulator 7g-4-1 located in the rear passenger side cargo bay on the upper back wall closest to the drive wheels. Hope this helps. Ray | ||
| Sean Welsh (Sean)
Rating: N/A |
Ray, Thanks, that helps. Philip -- the part# that Ray lists seems to be specific to MCI. I strongly recommend you purchase the MCI service manual for your coach, which should have full wiring diagrams. In any case, here is a document from MCI specifically on troubleshooting this regulator and the "Not Gen" problem: http://www.mcicoach.com/Parts-Service-Support/serinfo/serinfo0104.htm#54 Based on the descriptions in the troubleshooting guide, I am guessing the 7g-4-1 Regulator is a P-type. I am also guessing the stock alternator in an MC8 is a 50DN, and the unit you have is also a 50DN. I think this should work, but you will need to test this out first (use a meter to determine if the regulator is working properly, *before* hooking up the alternator field). So here goes. (Disclaimer -- I'm making some educated guesses without being able to see your setup. Don't blame me if this blows up!). Remove the jumper from POS to F1. Install a jumper from F2 to frame ground. Connect your F1 wire (that may previously have been connected to a terminal marked FLD) to F1. Your previous R wire should go to R or R1 (however it is labeled). I believe this should work. Your regulator is putting out a positive field voltage on its F1 lead, and you need to send this to the positive field terminal of the alternator. The negative field terminal, F2, now goes directly to ground. Hope this helps, and let me know how it comes out. -Sean | ||
| philip potter
Rating: N/A |
Sean, thanks for your help with this. It's been a few days until I could get back at this. Let me tell you what I know and you tell me if your advice still makes sense. 1.As stated before on the alternator I have the F1 wire on the F1 stud that has a bridge to the poss. post and the R1 wire to the relay. 2.The regulator has 3 post. NEG, which has two wires. a wire to ground on the frame and wire 36. FLD, which has wire F1 POSS which has a wire labled A1 (A1 is labled in my manual as 24v regulator) 3.The Air presure switch has 3 post. Wire 36 Wire 38 (labled in the manual as "low air tell- tale light") L2 (have not found this one in the book) I had already started the bus before with the wires hooked up in the present positions so I turned the power on and tested the post on the regulator (without the bus running) and the POSS post and the FDL post (with the F1 wire) were both hot. Have I already toasted something? Thanks for helping me understand how this system works! phil | ||
| Sean Welsh (Sean)
Rating: N/A |
Phil, Yes, this confirms what I told you should work. FLD on the regulator should go to F1 on the alternator. REMOVE the strap from F1 to POS (or BAT) on the alternator. Strap the alternator F2 terminal to ground. The A1 wire to the regulator is both battery voltage sense and "ignition" signal. Check that A1 is hot when the master switch is "On" and cold when the master switch is "Off." "Neg" on the regulator should go to frame ground. Start the engine. You should then get 12 volts on the "R1" terminal of the alternator, and a good 27+ volts out on the POS or BAT terminal. If you don't see these right away, shut the engine off and check all your wiring. I don't *think* you've fried the regulator, but I can't rule it out, either. If nothing has been connected to F2 on the alternator, you did not fry it. Let me know how it comes out. -Sean | ||
| philip potter
Rating: N/A |
All set. Thanks, Sean. When all said and done,(like you said) the alternator was just set up for another bus with a bridge from the Poss to F1 post that it did not need and no bridge from F2 post to ground which it did need. I quess I was originally stuck in the idea that the alternator was different and therefor set up differently to work. In reality the alternator was the same and had been set up for a different system that was in the donor bus. Yes, that's right, you had to go though all this just to get me to set up the new alternator to look just like the old one did. Sometimes a mind just gets stuck in the mud and needs help. It's great to have you electrically minded people around for help us less fortunate soles! the light now goes off at 90 lbs. pressure and it charges right where it should read. thanks again. |
