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Old 10-13-2021, 01:15 PM   #1
Bus Nut
 
Join Date: Oct 2016
Location: Pensacola and Crystal River, FL
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Year: 1998
Coachwork: AmTran International
Chassis: 3800
Engine: Navistar 7.6L
Battery Question

1998 international chassis AmTran bus.
I had to replace one of the two start batteries.
Had to replace ignition switch due to lost key, found key six months latter of course.
A week ago I was trying to start engine. Regular buzzer(s) when key at 1pm run position, regular cranking when turned to 2pm starting position and then spring return to 1pm run position.
Can turn to 11am position and one red light at upper left of control console on the left flashes slowly, no buzzer(s).
To let you know key is in accessory position?
Batteries were at 100% per charger a week ago. They drained down to 10% by today.
Key was definitely at 12pm, the only position where key can be removed.

The only electrical things that have changed since last time running is the new key switch, fuel level sensor wires not hooked up, and maybe the wheelchair lift has been removed since. Also not sure if rear door had an open alarm on it or not and may have been removed since last time running. It is a 1998 so maybe they did not exist. But there are no alarms sounding, but power maybe is still being consumed silently?

Also, with door switches removed and not jumpered correctly cause a "no start" condition??
i.e. maybe there is a n/c solenoid decompression of diesel cylinders that door switches might involved with?
In craanks over good but no runny. Other diesels without a bunch of safety switches like a school bus only need fuel, air, compression and turned over a few times to run.

I am going to charge up the batteries and then start pulling fuses to see if I can stop the drain.

P.S. I know it is not best practice to use an old battery with a newbattery. But the old one is still working fine on a weekly basis.
I do think the old battery would cause both to drain down?

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Old 10-13-2021, 01:35 PM   #2
Bus Nut
 
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Skoolies are notorious for phantom drain. In my case it stopped when I ditched all of the bus light controls and monitors and bypassed the door safety interlock. Itís best to pull all that stuff in the long term I think but otherwise a solar or small plug in trickle charger is your best friend.
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Old 10-15-2021, 12:28 PM   #3
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Find that phantom draw or install a cut off switch on the + battery lead, or BOTH!!

Lead Acid batteries don't like to be drawn down below 50%.


Good Luck.
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Old 10-15-2021, 07:44 PM   #4
Bus Nut
 
Join Date: Oct 2016
Location: Pensacola and Crystal River, FL
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Year: 1998
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Engine: Navistar 7.6L
Anyone know what this 90 amp breaker goes too?
It is inside the battery box and connected to positive post with 4ga.
Whereas the other positive and negative battery cables are like 2/0 size.
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Old 10-15-2021, 09:01 PM   #5
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Quote:
Originally Posted by DoubleO7 View Post
Anyone know what this 90 amp breaker goes too?
It is inside the battery box and connected to positive post with 4ga.
Whereas the other positive and negative battery cables are like 2/0 size.

Do you have a wheelchair lift? Thatís where mine was. But I donít think my breaker was that large.
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Old 10-15-2021, 10:44 PM   #6
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Quote:
Originally Posted by DoubleO7 View Post
Anyone know what this 90 amp breaker goes too?
It is inside the battery box and connected to positive post with 4ga.
Whereas the other positive and negative battery cables are like 2/0 size.
If you had a wheelchair lift, it likely was for that. It's also possible it's a main breaker for chassis or body electrical systems. My buses have a circuit breaker for each, but the wheel chair breaker is in the battery compartment instead of the engine bay. Its my personal practice that I open all breakers when storing my buses, helps guard against this sort of problem.
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Old 10-16-2021, 10:04 AM   #7
Bus Nut
 
Join Date: Oct 2016
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This breaker does not seem to have a way to turn it off. No reset button or trip level.
Auto reset?

Nevermind the above, should have groped around the one I have. The way it is mounted you can't see the flag that swings out from under the center hump.
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Old 10-16-2021, 01:38 PM   #8
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Join Date: Oct 2016
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Just got done looking for the battery drain, which right now is at 3.5 amps.
Pulled ever fuse in the exterior fuse box below drivers window.
Pulled every fuse out of the interior panel in the dash.
Disconnected the 90amp breaker mentioned earlier that did indeed go to the chair lift.
None of the above reduced the 3.5a draw.
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Old 10-16-2021, 01:59 PM   #9
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Do you have an amp clamp? I would start checking or isolating the main power wires. Not everything in a bus may have an accessible fuse, finding out which main wire actually has the amp draw on it and following it might be your best lead. You may even discover additional junction boxes you didn't know existed. Also check the alternator, occasionally those will fail like this too.
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Old 10-17-2021, 11:35 AM   #10
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Hello truthseeker,
You nailed it!
Disconnected red wire and white wire on alternator.
The 3.5amp draw went to zero. Reconnected only white wire, still zero draw.
Reconnected red wire, back to 3.5a draw.
I then used my meter to measure the draw between red wire and the alt. terminal, got the 3.5a draw there too.

Those two are the only wires to alt.
Any idea if it is something inside that can be replaced like a diode, etc.?
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Old 10-17-2021, 11:55 AM   #11
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Quote:
Originally Posted by DoubleO7 View Post
Hello truthseeker,
You nailed it!
Disconnected red wire and white wire on alternator.
The 3.5amp draw went to zero. Reconnected only white wire, still zero draw.
Reconnected red wire, back to 3.5a draw.
I then used my meter to measure the draw between red wire and the alt. terminal, got the 3.5a draw there too.

Those two are the only wires to alt.
Any idea if it is something inside that can be replaced like a diode, etc.?
Good to hear you found the issue.

As far as repair, that I don't know, I honestly don't know what causes the draw I just know it does happen. You can try to see if there's alternator repair shop in your area. There's one in mine (Arlington Armature) probably due to how many transit agencies there are in 50 mile radius. Those big alternators can be very expensive.
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Old 10-17-2021, 07:39 PM   #12
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I donít know that Iím sure that the alternator is the problem right away. The wire could be just bringing power to something else from the alternator and that connection and not necessary powering the alternator. That could be the source side of the power and itís feeding something else thatís causing the drain. Be sure before you yank the alternator.
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Old 10-17-2021, 09:10 PM   #13
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Quote:
Originally Posted by rffffffff View Post
I donít know that Iím sure that the alternator is the problem right away. The wire could be just bringing power to something else from the alternator and that connection and not necessary powering the alternator. That could be the source side of the power and itís feeding something else thatís causing the drain. Be sure before you yank the alternator.
That should be easy enough to rule out by putting a meter inline with the negative battery post in amperage mode and then disconnecting the alternator. If the draw disappears, then it's the alternator for sure.
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Old 10-18-2021, 09:47 AM   #14
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Chassis: 3800
Engine: Navistar 7.6L
Using my multi meter in the 10amp mode........
At battery, negative disconnected, meter lead on neg battery cable other on bat = 3.5 amps. Disconnect red wire at/from alternator = 0 amps.
Reconnected battery neg. cable and moved to alternator.
With meter on disconnected red wire and alternator terminal got 3.5 amps.
Reconnected red wire and did same as above to white wire got no amps.
There are no other wires connected to alternator, anywhere, just a red and a white (ground).
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Old 10-18-2021, 09:52 AM   #15
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Itís hard to think about this without seeing it but I guess what I need to know is if the red wire at the alternator has 12v on it when itís disconnected. If itís live when itís disconnected and there are no other wires on the alternator than I think you found your problem. If itís dead when itís disconnected (and thereís 12v on the alternator when that wire is missing) then itís feeding something else. Should be easy to check.
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Old 10-18-2021, 08:32 PM   #16
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Maybe just a fart in the wind, but on my bus the instrument panel is ALWAYS on, regardless of the ignition switch setting. 12v x 3.5a is 42 watts. It's something small. Like an instrument panel, or an ECU.
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Old 10-18-2021, 09:49 PM   #17
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Maybe just a fart in the wind, but on my bus the instrument panel is ALWAYS on, regardless of the ignition switch setting. 12v x 3.5a is 42 watts. It's something small. Like an instrument panel, or an ECU.
Generally speaking, particularly for cars, anything over half an amp is considered unacceptable after an hour or two of sitting. By that time all the modules in a car should have gone to into a very low power sleep state.

This past spring I ended up changing an instrument cluster in a Ford shuttle bus because it kept randomly powering itself on and killing the batteries. "Parasitic draw" really can be a pain to track down...
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Old Yesterday, 09:04 AM   #18
Bus Nut
 
Join Date: Oct 2016
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Year: 1998
Coachwork: AmTran International
Chassis: 3800
Engine: Navistar 7.6L
Hi Rusty,

You would likely get better answers to your questions by posting your post in the "electrical" catagory. Go to home page here, it is in the tech subjects section.

Good luck and welcome.

[moderator edit: Moved the post to a new thread…]
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Old Yesterday, 09:08 AM   #19
Bus Nut
 
Join Date: Oct 2016
Location: Pensacola and Crystal River, FL
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Year: 1998
Coachwork: AmTran International
Chassis: 3800
Engine: Navistar 7.6L
I am waiting on fuses for my multimeter so I can continue the draw testing in order to confirm the latest suggestions.
I am without any means to leave the house and get some this week.
The fuses are to arrive tomorrow.
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Old Yesterday, 10:52 AM   #20
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Take a picture of your alternator. Is the red wire you refer to going to the b+ terminal on it? If so, you might have a faulty diode. Depending on the alternator, you might be able to get a new rectifier and repair it. I've never replaced an individual diode.

White wire is likely not a ground, but a sense wire. Very few alternators have a ground wire, as the case itself is grounded to the engine and chassis.

I've seen diodes in the rectifier leak and cause a battery drain. I've also seen voltage regulators be faulty and cause a drain as well.

Does any part of the alternator feel warm to the touch? The last one vehicle I had parasitic draw on, I traced it to the alternator and you could feel the voltage regulator was warm to the touch with the vehicle off and cool, making the voltage regulator the obvious fault.

If your batteries are stone dead, charge them up real slowly. You might have a chance at saving them doing it that way. If you fast charge, or jump the bus to get it started, you'll very likely kill them in my experience.
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