| Author | Message | ||
| Mike Lester (Tin_woodman)
Registered Member Username: Tin_woodman Post Number: 12 Registered: 1-2009 Posted From: 72.213.22.46 Rating: N/A |
I wound up having to work Sunday and have worked late all week, so was not able to get out to the bus until tonight (I don't hve room to park at the house.) I checked voltage on the regulator field terminal and got some interesting if not baffling (to me) results. When the engine was on slow idle, I got voltage on the field terminal. Voltage on the battery was 13.5. When idle was kicked up, the voltage on the regulator would start to pulse on and off, which is consistent with what the "not gen" light is doing. Any further suggestions would be very welcome - while we are not traveling over the coming Memorial Day weekend, my SO and I had been planning a trip the following weekend. The park is only about 30 miles - can I drive it that far as is, worst case scenario? And put a charger on when we get there? If I can charge, do I need a charger for each battery or will connecting 1 12v charger work for the pair? As always, many thanks... Mike Lester | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 476 Registered: 3-2007 Posted From: 71.55.197.237  Rating: N/A |
Mike' what kind of coach do you have? If you have belt driven alternator, check the tightness of them, that sounds like what your problem is however you may have a regulator going out. There may be some unknown load on the battery and draining out the batteries, Check the belts first and see. Gomer | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1611 Registered: 12-2000 Posted From: 76.68.132.83  Rating: N/A |
The big alternator, if you are lucky, gives you a short warning and then fails completely. Pulsing lights usually means rebuild time for the alternator. The nice thing about an analog bus, you can run it without electricity! I don't see a problem with a 30 mile jaunt in the daylight, the only power out of the battery would be to start the engine and then the turn signals and brake lights to destination. happy coaching! buswarrior | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 837 Registered: 8-2006 Posted From: 76.171.79.185 Rating: N/A |
As I remember, it is an MCI, which means 24 Volts. That means two 12V chargers, one on each batt, before and after the trip. Drive it, and tell us more when you get a minute. Specifically what the reg batt terminal voltage to ground is, when this happens. Field voltage can drop to only one or two volts, with charged batts and no load on a properly working system, at high idle, or above. Field voltage is an indication of how much current the regulator is asking the alternator to produce, the more field, the more output. No field=no output. Happy hunting, George | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1085 Registered: 12-2000 Posted From: 71.3.157.139  Rating: N/A |
Mike has an MC-7 (24 volt). I do not remember whether the alternator is gear or belt driven. Should be no problem driving it 30 miles. You will need to charge each battery separately or use a 24 volt battery charger. Jack | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 366 Registered: 2-2001 Posted From: 69.77.144.28 Rating: N/A |
Mike, our Eagle has the big 50DN gear driven alternator. It is rebuilt with 800 milles on it. It pulses as you mention such that you can see the dash & headlights pulse. But when I turn on a big load, like the fans for the over the road air, it straightens right out. I have been told that these sometimes pulse when they don't have much work. It might be that your batteries are pretty old & won't take much charge rate? Mine are pretty old. If you have access to some young batteries, you might see if that makes a difference. | ||
| Len Silva (Lsilva)
Registered Member Username: Lsilva Post Number: 236 Registered: 12-2000 Posted From: 24.164.20.23  Rating: N/A |
I think Jim hit it on the head. If the batteries are fully charged or defective then it's just the regulator trying to do it's job. Try turning on all the lights and see if the pulsing goes away. If the pulsating is in time with engine speed rather than load sensitive, then it's most likely a bad diode in the alternator. | ||
| John Lacey (Junkman42)
Registered Member Username: Junkman42 Post Number: 82 Registered: 3-2007 Posted From: 66.82.9.13  Rating: N/A |
Mike, if You are not an electronic type but have a buddy that is have Him or Her look at the dc alternator output with a O'Scope. If a pulse is missing it will be obvious to a electonics type person. A missing pulse or a pulse that is flat topped will indicate a shorted/bad diode in the alternator. Regards John | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 838 Registered: 8-2006 Posted From: 76.171.79.185 Rating: N/A |
There are indeed six diodes in these type alternators, and they run in three pairs. If one diode fails OPEN, 1/3 of the output is lost, per revolution of the alternator, which is at least twice engine speed. So, at idle, the alternator is going to be turning at least 750 rpm, which would be 12 dips per SECOND. Pulsing is caused by a high resistance connection somewhere in the circut between the master switch, the regulator, the reg ground, or the alternator field circuit. A shorted diode grounds the batteries, and disappears after letting its smoke out! Pulsing can be caused by an open capacitor in the voltage regulator, which will cause Jim's symptoms. Tighten the connections, clean the grounds, and lets see what happens, I really feel it is not a bad alternator. G | ||
| Mike Lester (Tin_woodman)
Registered Member Username: Tin_woodman Post Number: 13 Registered: 1-2009 Posted From: 72.213.22.46 Rating: N/A |
Very glad to hear we can proceed with our trip next weekend! The voltage is normal and the light on the dash does not flash at idle, but does at higher rpm. The batteries are brand new, and I cleaned the terminal ends before installing. I did not clean the grounds on the chassis, but will give that a try. Unfortunately, I no longer have access to an oscilloscope, so can't do that check. Thanks again - I'll let you know what happens! Mike | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1288 Registered: 5-2001 Posted From: 65.74.69.200 Rating: N/A |
Mike, if you hear regular engine surges at idle while you are getting the voltage surges, and the engine slows right when the voltage climbs, that is pretty good proof the alternator and regulator are doing their jobs. On our 4106, after the engine has been running a couple of minutes, the engine slows and the lights brighten. Then the regulator shuts the field off and the engine speeds up. On cars and a lot of other equipment, the regulator turns on and off so rapidly that you don't see or hear the changing output; ours will take a second or more to go through a slow and fast cycle. That's just how long the regulator is on or off for each time the altermator is working. It seems to cycle quicker and have smaller pulses when it is working hard. The power applied to the field at any given time is either full battery voltage or nothing, so a digital meter does not read this very well. If you use an analog meter, you can easily see the effect. For what it's worth. Tom Caffrey | ||
| Tony LEE (T_lee)
Registered Member Username: T_lee Post Number: 60 Registered: 11-2007 Posted From: 59.154.2.62 Rating: N/A |
When my 50DN failed, I drove the bus for several thousand km without an alternator. Just powered the engine battery from the house system. Mine sometimes pulses (I can hear a relay clicking somewhere in the driver AC unit). Switching the headlights to low beam (usually done as a safety measure anyway) fixes it. | ||
| Mike Lester (Tin_woodman)
Registered Member Username: Tin_woodman Post Number: 14 Registered: 1-2009 Posted From: 72.213.22.46 Rating: N/A |
Well, per George's suggestion I cleaned the grounds. At first it didn't make any difference, but they everything returned to normal within a minute of when the bus made air. May be that was it, or as Len said the regulator was just trying to do it's job. I dunno...but **yay** it's working! And, I know a lot more about that system. Thanks everybody! | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1093 Registered: 12-2000 Posted From: 71.3.157.139 Rating: N/A |
Mike, Glad you got it fixed. As far as not working until you had air pressure. That is normal. The system is designed so that the alternator and OEM AC would not work until there was adequate air pressure to maintain proper belt tension. Jack | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 754 Registered: 7-2006 Posted From: 75.209.170.4 Rating: N/A |
Good show, George...and congratulations, Mike...what a GREAT, FREE board this is, correct? THANX Ian!!!  RCB |