| Author | Message | ||
| John that newguy (199.232.240.195) Rating: N/A |
I have a 40-50 ohm draw on the battery lead when the 24v circuit is on, with nothing running; key in off position and all lights out. It's dragging down the battery unless I turn the power switch off when I leave the coach overnight. I (think I) traced it back to the rear panel, but haven't disconnected the two connections found at the panel exterior side. One lead goes to the alternator, the other feeds the box. Before I rip anything else apart (scalp included), does anyone, or has anyone, had this problem and a cure? | ||
| TWO DOGS (65.179.193.32) Rating: N/A |
I'm damn sure no electrician...guess I'd start by disconeting wires & when the draw dissapears,that was the bad circut | ||
| TWO DOGS (65.179.193.32) Rating: N/A |
I've also heard that a bad diode in the alt. can do the same thing.. | ||
| Jim-Bob (64.12.116.135) Rating: N/A |
John, disconnect the alternator wires & see if the battery stays up. You may have a shorted diode in the rectifier. If shorted, it would back feed & keep the windings energized with the engine off. You also can tell if you turn the battery switch on with a cold engine. Leave it on for an hour or two and feel the winding frame. If it's warm, you have a problem. If your voltage regulator is energized by an oil pressure switch or similar, that may be keeping it energized with the ign. switch off. | ||
| John that newguy (199.232.244.175) Rating: N/A |
Re: "If your voltage regulator is energized by an oil pressure switch or similar, that may be keeping it energized with the ign. switch off." Hmmm.... I'd rather find that, than replace the alternator. Any suggestion on where a novice would locate that? I'll be headed over to the bus this morning to try to pin down the draw. What's making this tougher, is the fact the engine was swapped and the transmission changed from a Std to an auto. Both jobs leave quite a bit to be uhhhh... well... I've been finding wires off, sometimes taped, sometimes not.. air lines off.. It's a typical Church bus. If it weren't for the manuals I got from Chuck Lott, I'd be a lost fool. | ||
| bruce king (67.170.101.3)
Rating: N/A |
Doesn't the door have a solenoid that keeps it closed and is engergized constantly? The relaxed position for hte solenoid is door open. maybe i'm crazed. | ||
| John that newguy (199.232.240.132) Rating: N/A |
ACK. Ok, I found that there's a 40-50 ohm load across the hot terminal (battery feed) of the alternator, to ground. The rest of the system is clean. I guess it'd be safe to assume that's what's pulling the battery down? While I go look through Da Book and pull out what little hair remains on my head.... If someone knows if or if not there should be any resistance from that terminal to ground, I'd appreciate it. The alternator seems to work ok, although the initial start-up voltage of 32 volts bothered me (I since found that's normal). And the normal voltage runs about 27.5, which is what Da Book calls for. I've found a minor bit of resistance on the front leg of the 24v system, but it didn't seem to me, to be enough to drag an 8d down overnight. Or would it be? (could be that door solenoid) Input welcomed, as usual. Don't be shy, even "crazy ideas" have often been proven to be the only correct ones. | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
John, an ohmmeter will give you a false reading when dealing with semiconductors, if you are interested in learning what current is drawn by these devices. You need to have full or nearly full voltage applied to learn the load they represent, which means reading the draw with an ammeter such as a DVM. To do this, remove a battery cable from a post while the ammeter leads are connected to both. If you just connect the leads when the cable has been off a while, there may be a big surge of current as you make the connection. Another way to do this is to connect an ammeter across your battery switch while it is turned on. When you shut the switch off, you will have all the flow through the meter. Once you have the current flow in amps, you just divide that number into the amp hour ratings of the battery bank to learn how long in hours it would take to discharge the fully charged battery. From there, you should be able to figure out if that load is running your batteries down. One thing about your readings: if you actually have a low resistance load, that means you will get a large current. What you want is readings near infinity, not low ones. HTH Tom Caffrey PD4106-2576 Suncatcher | ||
| John that newguy (199.232.244.127) Rating: N/A |
You'll have to type a lil' slower Tom, I'm not quite "with it".. How much resistance should there be with this alternator, from the battery terminal on the alternator, to ground? (The manual states "5.7 to 6.2 amps at 24 volts" is normal for this alternator, with a charged battery) I've had one local "expert" tell me it's very normal to see a near short between that terminal and ground using a meter, but under power, it's nothing to be concerned with. If so, I'll start looking at the other 24v leg that feeds the front panel and be thankful. (wow.. sharp learning curve! wATTA RusH) | ||
| John that newguy (199.232.244.127) Rating: N/A |
Hey Jim-Bob..... Remember your earlier comment on Friday, August 27, 2004 - 10:33 pm: "John, disconnect the alternator wires & see if the battery stays up." Well.... I just read it again on Sunday, August 29, 2004 - 07:51 am. I think I'll do that today, instead of fooling with a meter. Your suggested test may take longer, but what better test could there be? I've tested almost everything in life using that method. It ain't failed me yet.. I should have done that Friday.... | ||
| ChuckMC9 (Chucks) (66.167.142.132)
Rating: N/A |
"It's dragging down the battery unless I turn the power switch off when I leave the coach overnight." Well, if it were a Micro$oft product, they'd say, "The solution is to turn off the power switch when you leave the coach overnight."  Not that you probably don't want to trace this down anyway, but seriously, the MCI guys told me to always turn that switch off even though I don't think mine draws any current anyway, but have never checked. One more theft prevention roadblock anyway. | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
John that newguy, the resistance of the field winding of that alternator looks to be 4 ohms, if the figures you've given are correct. If a load like that was left on for 24 hours without any source of power to replace it, it would be around 150 amp hours. That's about 2/3 of a full charge on two 8D batteries. That's enough power to heat up your alternator about as much as one big light bulb or two ordinary ones (150 watts). You would have no trouble feeling the warmth in your alternator. Does that help you? Tom Caffrey PD4106-2576 Suncatcher | ||
| John that newguy (199.232.244.167) Rating: N/A |
Update? After all day with the master disconnect -on- and the bus sitting, minding it's own business... the batteries remained fully charged. So I said "whaaadah^%^$%"#*......???" The alternator is hitting the batteries with 32 volts initially, until the air's up and into fast idle. Then it drops to the normal 27.5. I left it all connected and will check tomorrow again. Hopefully it's only due to a loose battery ground that I tightened since beginning this trek down aggravation lane. I did notice another "odd" occurrence. Maybe someone can shed some light? With the fast idle on and the bus air on and the system charging as it should.... when I turn off the bus air conditioner, the engine speed decreases for a second and the "not generating" light comes on for a moment. A problem in the making? Is there something common to all these problems? Or am I looking at a very bleak future of electrical woes? Will all these problems with this former church bus resolve by itself if I become a Baptist? An inquiring mind wants to know.. (Tom... The manual says there should be 4-5 ohm resistance to ground from the field terminal. Am I lost here?) | ||
| ChuckMC9 (Chucks) (66.167.165.236)
Rating: N/A |
Couldn't dance with Two Dogs' wife if you did that. | ||
| John that newguy (199.232.244.238) Rating: N/A |
Put a whole new meaning to "Holy Roller"? | ||
| Tom Caffrey (Pvcces) (65.74.66.104)
Rating: N/A |
John that newguy, "(Tom... The manual says there should be 4-5 ohm resistance to ground from the field terminal. Am I lost here?)" John, see my previous post.... "John that newguy, the resistance of the field winding of that alternator looks to be 4 ohms, if the figures you've given are correct." How close do you want to get it? HTH Tom Caffrey PD4106-2576 Suncatcher | ||
| John that newguy (199.232.240.18) Rating: N/A |
Well... It's been well over 24 hours and the batteries are still in fine shape. I guess the book's close enough, claiming a minimum of 4 ohm resistance is fine. No less, as that would indicate a shorted diode; An open diode would give a high reading. So... whatever caused the batteries to drain, is apparently gone now. A stuck relay, a sensor... who knows...? Poking and moving wires in the rear cabinet may have accidentally removed the problem. But one thing's certain.. If you're checking for a load on the circuit that might be pulling your battery down, disregard the 4-40 ohm resistance from the alternator. The book says it ought' be there and I oughta' know better than to question Da Book. Thanks for all the suggestions, guys. If that problem occurs again, I'll look at all the stuff mentioned. | ||
| ChuckMC9 (Chucks) (64.105.16.193)
Rating: N/A |
But turn the switch off anyway! | ||
| TWO DOGS (63.185.73.195) Rating: N/A |
yeah....it would be better if there were never any problems with the battery drain syndrome...even if a mouse 'creates' one for you while you are gone,turning the main breakers off prevents you from seeing only 'embers' when you return.. (the other subject) scandal in the south ,one time,....... it was terrible...bunch of 'swingers' got together ...& a dance broke out... | ||
| Stan (68.150.152.113) Rating: N/A |
John that newguy: Your various posts and replies have a lot of confusion in them. You have talked about measuring the main battery terminal and then referred to the field. These are two different things and not connected inside the alternator. The field winding is on the armature and is fed from the voltage regulator through slip rings on the end of the armature. There are no diodes in this circuit. The main battery terminal is connected to an internal three phase diode bridge to the stator windings in the alternator. If you are drawing current on the field winding when shut down then the voltage regulator is faulty or else it is not being turned off. It is controlled by a relay that is switched by the R terminal on the alternator if you have a DN 50 alternator. | ||
| John that newguy (199.232.240.137) Rating: N/A |
There is a 40 ohm resistance from the battery terminal on the alternator, to ground. It's safe to assume that the diodes are producing that, since reversing meter polarity eliminates that resistance indication. The manual claims that resistance is normal and indicative of a working diode array. In attempting to locate the source of the draw on the battery, I simply followed the "short" I was seeing to the source. I now know that wasn't the source of whatever was drawing the batteries down. As a side note.. I noticed that the turn signal flasher clicks continuously with or without the key on. No lights flash. but there is a sizzle/clicking sound from it. I will disconnect that until I get a replacement.. It appears to have been added to the system in a half-fast manner. (I'm not too quick either) |