| Author |
Message |
Kevin Hatch
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 12:52 am: | |
On my 4905 all of the running lights and the head and tail lights pulsate pretty noticeably. It's bad enough that you see the light pulsing on the road in front of you at night. The volt meter pulses between about 25-26V and 28V. I have noticed that it pulses faster and maybe a little harder when the lights (head, tail, and marker) are on. Would this be the voltage regulator? Suggestions?
Thanks!
Kevin Hatch
1970 PD-4905 |
JW Smythe (Jwsmythe)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 4:33 am: | |
Does the pulsing change speed with the engine RPM's? If so, on any other vehicle I'd say yes, voltage regulator. The same probably applies to the bus. |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 5:24 am: | |
You could have a cople of alt diodes gone.
Most likely tho it could be the imbecilic bus volts regulatior.
Does the red "not charging" light come on with the blinking? then it IS the V reg.
FAST FRED |
Casper4104
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 7:02 am: | |
You know, motorcycle guys pay good money for a gizmo called a "Headlight pulsator" that does the same thing. The idea is that the pulsing/flashing headlight makes you easier to spot, and hopefully nobody will make that left turn in front of you. "I'm sorry officer - I never saw the motorcycle".
Probably not a problem with the bus, we're pretty hard to miss and I've never heard "I'm sorry officer, I never saw the 40 foot long, 12 foot tall, 8-1/2 foot wide dayglo technicolor bus".
Good luck, hope you get it sorted out.
Casper4104 |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 9:12 am: | |
Hello Kevin.
I'm with FF. Pulsing is a good indicator that your big alternator is being kind and giving you a brief warning that it is about to fail.
Unless you have a redundancy for making your 24 volts to get home, best to get to this right away. These big alternators, once on the way, fail quickly.
Get out your books and do the tests on the diodes. Whether you have space to do it without removing the 85 pound beast from the bus, well good luck!
Though the stock voltage regulators are dumb brutes, (compared to the more battery friendly multi-stage modern ones)they are usually pretty reliable in their unsophisticated ways.
Check the flea market for potential replacements.
happy coaching!
buswarrior |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 9:13 am: | |
Kevin,
You probably have a short and a resetable breaker resetting then opening. If this is true you'll want to fix it soon or the breaker will destroy itself.
Often one can hear the clicks as the breaker opens and this helps locate which breaker is trying to carry a short.
Regards
Jerry 4107 1120 |
Kevin Hatch
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 9:33 am: | |
The pulsing doesn't change with the RPMs. It only changes when under more load. I have noticed that you can kind of hear a little bit pulsing at the rear of the bus. I'm sure it's the alt. whining. However, if you can hear that OVER the DD on fast idle, it's probably pretty loud! What are the chances of just finding a replacement alt? Are they hard to rebuild?
Kevin |
Frank Allen (Frank66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 9:53 am: | |
Fred, you keep talking down the GM regulaor, why? ive never had a problem with mine, what do you have in there??
Frank Allen
4106 |
Charles Seaton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 9:53 am: | |
Sorry casper,
NY motorists run into buses quite often. What is their main excuse? You got it. I didn't see the bus. |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 10:27 am: | |
Hello Kevin.
What is the frequency of this pulsing?
Once every so many seconds, or?
happy coaching!
buswarrior |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 10:34 am: | |
Kevin,
FIND THE SHORT. You, almost certainly, don't have an alternator problem. All conversions disconnect many things from the stock electrical system. One of the disconnected circuits has probably become a short and is repettively tripping it's breaker. It could be part of the original air conditioner or lighting or restroom wiring.
As to the alternator you can test the diodes without removing it from the bus. I've replaced the stator of mine without removing the rotor. It's also possible to remove the field without removing the rotor. Removing the rotor is tricky as bearings and seals will have to be changed. So in kind of summary the electrical parts of the alternator can all be removed/repaired/replaced without removing the rotor and bearings and seals.
Regards
Jerry 4107 1120 |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 10:37 am: | |
Yup, Jerry's got a good point.
If the left over wiring has not been properly terminated....
Sky is the limit for trouble!
happy coaching!
buswarrior |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 10:57 am: | |
Kevin,
Here is how to find the short. Open the covers of all the places where circuit breakers are, such as the driver's panel, the HVAC compartment, the engine compartment and any others on your model bus. Start the engine then probe, with your voltmeter, each end of all the circuit breakers. On one you'll find that the voltage drops to 0 when the rest are pulsing to the lower voltage. After shutting down and dsconnecting the battery, remove the wire(s) from that breaker. Re connect the battery & restart and the pulsing should be gone, if not continue probing and repeat till it's gone. Once you've eliminated the pulsing consult your manual & determine if you need what you've disconnected. If you aren't using that circuit anyway you are done but if it's something you want you'll need to find and remove the short.
Regards
Jerry 4107 1120 |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 11:19 am: | |
Kevin, due to the time delay inherent in circuit breakers tripping and the time it takes for them to cool off before they re-set, I seriously doubt you have a short. I also seriously doubt if it is a bad diode in the alternator.
Over the years I have seen this pulsing problem discussed on the boards but the problem was never, to my knowledge, traced to a short circuit. A couple of times it was just a load was needed on the alternator.
Please let us know what you find. My guess would be voltage regulator or some bad battery connections.
Richard |
Jerry Liebler (Jerry_liebler)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 11:53 am: | |
Richard,
I for one have had the problem of pulsing and found it due to a circuit breaker tripping. The pulses were about 1 second low and 3 seconds high. The offending circuit was one for the lavatory alarm which has been long gone.
Regards
Jerry 4107 1120 |
Buswarrior (Buswarrior)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 12:11 pm: | |
Kevin, more info, quick!
The natives are getting restless!
All of this info is good and factual.
There is nothing wrong with having different priorities based on our own experience!!!
Cool drink, anyone?
happy coaching!
buswarrior |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 1:55 pm: | |
Jerry, I really should have been more specific. I understood that Kevins lights were pulsing at a much higher rate. I do not believe the breakers on my Eagle would have pulsed as fast as yours were. But that is why the board is here to give the members as much potential information as possible.
Richard |
Kevin Hatch
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 5:12 pm: | |
Sorry fellas! I was away for a while. The pulses are 1-2 per second on the low end (lights off) and around 3-4 per second on the high end (lights on aka more load on the alternator). Thanks for the intrest and the input!!
Kevin |
Jim-Bob
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 5:24 pm: | |
Kevin, my Eagle does this too. If I turn on the bus air/heat blowers, it stops. I believe the regulator is not sensitive enough to keep the voltage right on the money. By the way, I had my DN 50 alternator overhauled, there wasn't anything wrong with it. If it stops when heavily loaded, it is most likely the regulator. |
Gary Carter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 8:54 pm: | |
Don't know the circuit of the 4905, but the 4106 had a relay in the sence circuit which also supplied power to the regulater. The contacts would burn and change resistance. If you have one find the relay and clean the contacts. |
John Jewett (Jayjay)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 26, 2006 - 10:31 pm: | |
Hey Kevin. lots of advice above and most of it useless, from people that don't own a 4905. Your problem is quite common to the 4905. (Mine included) and when I first got mine it drove me nuts trying to fix it. SOLUTION? There is a diode in the drivers control panel that provides the 12 volt feed to the ultra-low beam headlights that burn all of the time. That function was supposed to be a safety feature in those days. The Greyhound drivers went crazy, what with everybody flashing their headlights to get the 'Hound to shut it's lights off during the day. (GM tried that silliness again a couple of years ago didn't they?)It senses a slight voltage fluctuation from the voltage regulator and acts like a Hall Effect switch...going low then hi over and over.You can replace the diode (even going bigger, which won't help), you can adjust the regulator to stop it too, BUT you have to go 29.8 VDC to stop it, and that's too high. I've never seen one pulse the markers too, but the way your headlight switch is wired could cause that. Years ago, I asked the 'Board about it for a quick fix and was told definitely that the alternator was going bad. That was 6 years and 25,000 plus miles ago, and it's still working. Don't worry about it, there is nothing seriously wrong! no imminent alternator failure, no loss of lights, no fires, nothing. Just get used to it...and the folks who comment about in parking lots and truck stops. Replacing the headlight thermal reset breakers in the drivers storage locker will help too, since they get weak with age and contribute to part of the circuit and problem. Cheers...JJ BTW, email me off the 'Board for a phone number, and I'll talk more about it if you wish. |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 12:12 am: | |
Kevin, what we found with ours was that the voltage regulator would turn on the alternator and then shut it off. As it did so, the voltage would spike and fall.
With a battery that needs a recharge, the effect mostly disappears; with a battery topped up and little load on the system, the spike effect was pretty pronounced.
The imbecilic regulator is dumb AND slow. The old regulators on cars turned on and off at about 400 cps, so you couldn't see any flicker, most of the time.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 12:13 am: | |
Kevin -
Re:
"The volt meter pulses between about 25-26V and 28V. I have
noticed that it pulses faster and maybe a little harder when
the lights (head, tail, and marker) are on. Would this be
the voltage regulator? "
Read Jim-Bob's comment again. It make good sense!
(The techno guys get carried away at times, but they mean well!) |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 12:14 am: | |
Uhh... and Tom's!!! |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 27, 2006 - 12:29 am: | |
Kevin -
I had the same "problem" on my MC9, the lights (all the lights)
would pulse. My batteries were also boiling down; losing water.
I adjusted the regulator to just over 25v and the problem is gone!
Try adjusting the regulator lower and see if the problem
disappears, before you throw good cash at a non-problem. |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 30, 2006 - 8:36 am: | |
Kevin -
Did you fix it? If so, what was the problem?
It'd be nice to find the "fixes" for the "problems", in the archives! |
Jim-Bob
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 30, 2006 - 10:41 pm: | |
Hopefully, JayJay, you weren't talking about me when you spoke about worthless advice from people who do not own a 4905. I own the Eagle, a 4905 & a 4104. The Eagle behaves as he mentioned, but the '05 & 4104 do not. All three buses have virtually the same alternator rig. It is the oil cooled, gear driven DN50 Delco alternator & matching regulator. (The '05 is 24 volts but the others are 12) (BTW, the 4104 did not come with this rig but has been retrofitted.) |