| Author |
Message |
Tom Caffrey (Pvcces) (64.114.233.142)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 07, 2002 - 10:38 pm: | |
We are having a slow starting generator symtom in our 4106. As I pick up the RPM to the point where the generator light goes out, the light starts to flicker. If I raise the RPM some more, it goes off more of the time.
So far, if I drive the coach a ways, the generator has always come on and stayed on after some of this flickering business.
The flickering seems to last longer if we have used enough battery overnight to take a full charge (220 to 240 amps) for a little while.
I have studied DA BOOK and can't find anything that talks about a symtpm like this. Has anyone run across this sort of thing before?
Tom Caffrey PD4106-2576 |
Bradd B. Smith (Bbsrtbusproject) (208.26.165.67)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 08, 2002 - 1:34 pm: | |
I am really glad you asked this question. My guage say's 13.5 to 14 volts. The no gen light blinks on and off. Higher rpm makes it flicker and just before it shifts to third it goes out, then back to blinking in third. If I turn on anything or hit the brakes, it goes out and stays out until I turn it off or let off the brake. My local mechanic rebuilt the 24 volt alt and for a few days the light stayed off. Then it started again, I pulled the 24 volt and re-tested it, it is fine. Sure hope someone can answer this question. |
Tom Caffrey (Pvcces) (64.114.233.202)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 08, 2002 - 10:11 pm: | |
Hi Bradd, our symptom seems to differ from yours in one way. Our voltage reads 12 to 12.5 when the light flickers.
Since yours shows regulated voltage, your unit must be doing more charging than ours is when the light fickers. There is a circuit that is supposed to maintain a small charge rate so that the starter safety relay stays on.
On 12 volt units, it is a 20 ohm 20 watt resister in series with a diode. If appies a small current to the generator field terminal so that once the generator is charging, it doesn't drop out again until the engine is shut off (normally).
If that circuit does anything else, I haven't been able to figure it out. DA BOOK is silent on how it works. You might check to see if your relay terminal voltage falls off in step with your light flickering on. If it does, your resistor and diode circuit may not be working right.
Anybody else have any ideas?
Thanks.
Tom Caffrey PD4106-2576 |
mel 4104 (208.181.100.86)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 09, 2002 - 12:14 am: | |
hi tom you might try cleaning all ofyour ground connections as they can give you a lot of intermittit troubles like dim or flickering lights and gauges that read all over the place. they get a lot of oxide under them and become a intermitit connection just take them apart clean the ends and spray them with a contact cleaner , and put them back together and spray will a battery post conditionerto keep out the moisture. mel 4104 |
Buswarrior (Buswarrior) (64.229.214.184)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 09, 2002 - 7:21 pm: | |
Hello folks.
Here's my mechanic's words on the "no gen" light being on or flickering when it shouldn't:
"The No Gen light is controlled through a relay that is energized from the relay terminal on the back of the generator. The relay terminal outputs 1/2 of the charging voltage (i.e. approx. 6 volts for a 12 volt system or 12 volts for a 24 volt system) when the bus is running and charging. I imagine that highway coaches are the same.
If the generator fails the output voltage will drop and the relay terminal voltage will be too low to energize the relay. The light will then ome on.
It is important that the correct voltage relay be installed if it is changed (i.e. 6 v or 12 v Normally Closed). Also check the wiring and connections from the relay terminal to the relay itself for loose, broken or corroded conditions."
On the flickering "no gen" light, hats off to Tom, this is my mechanic's responce to Tom's post:
"This is correct and could be the cause of a flickering Gen Light. In theory, with no load on the bus (all accessories off) and the batteries fully charged, the generator output will start to drop off since there is no demand for voltage. This will cause the light to flicker on & off as the regulator pulses current to the field terminal in this no-load situation. I know GM installed a resistor in all the transit buses that would place a load on the charging system at all times, even with all accessories off. More than likely the same for the highway coaches.
The easiest way to check if this resistor is still working (or has rotted away) is to turn on the vehicle lights or heating blowers. This increases the load on the generator. If the Gen Light stops flickering then the problem is likely with the load resistor."
happy coaching!
buswarrior |
OAE Palmer (208.164.96.50)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 5:34 am: | |
Buy your mechanic friend a cold drink for all of us electrophobics & this moron!
(that ought to be at least a 6-pak)
The is nothing like straight forward info to make learning EZ.
Thanks for the pass along, it made my final task for the day (@ 3am!) ALL WORTHWHILE. |
FAST FRED (63.215.226.236)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 5:48 am: | |
I have found that the coach was DESIGNED to operate those big blowers in the bays at all times, so when that load is removed the system will be a hassle.
Biggest hassle is when the light is OUT the system is charging the batt , for hours on end , wheather the batts needs it or not.
ON a long ride even 13.8V, will heat , and may boil the batt over 14V definatly is unhealthy.
Driving with the headlamps , and a blower on keeps the light from flickering , but keeps the batt charging too.
I simply lowered the charge voltage to 13.2 to 13.4 that the batt can take for long periods.
This made those E$pensive Halogen Headlamp bulbs last too.
My 120V charger holds this on the coach for days with no ill effects , but it has a "brain".
AS the batt theoretically might still be not fully charged (although after 12 hours it would seem hard) I use the 14.4 output of the 120v charger overnight , about once a week , just to be sure.
Seems to work just fine , NO MORE FLICKER!
FAST FRED |
Bradd B. Smith (Bbsrtbusproject) (208.26.165.91)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 2:55 pm: | |
Many thanks my friends. My thoughts echo OAE's. Just got an electrical diagram from a man on the flea market board. With the slightest load on, it quits. Will find that load resistor and test it. Thanks again to all who responded, seems to have answered my question. |
Tom Caffrey (Pvcces) (64.114.233.209)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 4:31 pm: | |
Thanks all for your help. I will be checking out the resistor, connections and also see what the generator puts out on the resistor alone.
I say this because DA BOOK says that the regulator is not affected by temperature and when we're on a long run, I noticed the voltage getting up close to 14, which seemed a little high.
Maybe the batteries had enough and the generator was still putting out too much power. We'll see.
Tom Caffrey PD4106-2576 |
Dallas (216.98.68.82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 7:33 pm: | |
If you have a carbon pile regulator, or a newer upgrade, temp may be a factor. However, how many years/miles has this generator (not Alternator) been running? Check the brushes. If there isn't enough spring tension to keep the brushes tight against the armature, you will get an intermittant open, letting the light come on momentarily.
Dallas |
RJ Long (Rjlong) (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, July 10, 2002 - 7:56 pm: | |
Dallas -
IIRC, the OEM alternators on the 4106 and later GMCs are a brushless design. . .
RJ
PD4106-2784
Fresno CA |
Tom Caffrey (Pvcces) (64.114.233.254)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, July 11, 2002 - 11:21 pm: | |
Dallas, RJ has it right for our coach, if DA BOOK isn't wrong. It says that there are no brushes and does not require periodic maintenance.
Thanks for the idea. It just happened that I had already looked that one up beause the alternators that I have seen have all had brushes.
Tom Caffrey PD4106-2576 |