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Old 10-05-2018, 08:04 PM   #71
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Quote:
Originally Posted by sajohnson View Post
For some examples, I used this calculator:
https://www.calculator.net/voltage-drop-calculator.html
1) I entered: copper; 1 AWG; 14Vdc; single set of conductors; 5 feet; 1 amp. Voltage drop = 0.0012 volts.
2) All the same except 50 amps. Voltage drop = 0.062 volts.
3) Same except 100A. Voltage drop = 0.12 volts.
Thereby demonstrating Ohm's Law: V=I*R ... voltage = current times resistance.

The cable has a fixed resistance, so raising the current by a factor of 100 raises the voltage drop by one hundred.

Rearranging it to R = V/I we can see that your length of cable has 0.0012 ohms resistance.

--dick
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Get YOUR Sprinter's full configuration datacard by entering your VIN to https://www.datamb.com/
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
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Old 06-14-2019, 04:07 PM   #72
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Hello everyone,
Thought I would share my experience so far...
2007 Freightliner Sprinter 3500
Alternator replaced ~2 year ago (diesel mechanic shop) ~ $700
MB Battery Replaced ~2 months ago (myself) ~ $250
Y-cable replaced ~ 2 weeks ago (MB dealer) ~ $700

Still have battery light light on with no charge (tested at the battery)
Should I take the van back to the dealer or take it to a different Sprinter Specialist altogether?

As a side note...
Iím wondering if my charging system to house batteries is causing a malfunction in the chassis charging system?
Iím running a 300 watt inverter which powers my 70amp fridge and 10amp smart charger?
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Old 06-14-2019, 07:20 PM   #73
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

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Originally Posted by will902 View Post
Hello everyone,
Thought I would share my experience so far...
2007 Freightliner Sprinter 3500
Alternator replaced ~2 year ago (diesel mechanic shop) ~ $700
MB Battery Replaced ~2 months ago (myself) ~ $250
Y-cable replaced ~ 2 weeks ago (MB dealer) ~ $700

Still have battery light light on with no charge (tested at the battery)
Should I take the van back to the dealer or take it to a different Sprinter Specialist altogether?

As a side note...
Iím wondering if my charging system to house batteries is causing a malfunction in the chassis charging system?
Iím running a 300 watt inverter which powers my 70amp fridge and 10amp smart charger?
Just as a starting point, you could check the voltage both with and without the engine running.

If you check it after it's been sitting for a couple hours, it should be about 12.7 volts.

With the engine running it should be about 14.0-14.1 volts.

One crude but easy way to see if an alternator is working is that at night, with the headlights on, when you switch the engine off the lights should dim noticeably. If the intensity remains the same then the battery is not being charged. Obviously it's better to use a meter, but it you don't have one that's one way to tell.
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Old 06-15-2019, 05:44 PM   #74
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Well, i'd certainly *start* by disconnecting the Sprinter-side from the inverter.

Which size alternator did you *originally* have? What size engine? Did you have the "intelligent" battery system?
(these questions can be answered from your datacard, available from https://www.datamb.com/ )

If you have the 4-cylinder (was that an option in 2007?), the alternator system ain't simple, and theoretically requires programmed adaptation to the Sprinter's ECM. Was your "diesel shop" capable of doing that?

Your inverter could simply be subjecting the Sprinter-side to wacky high-frequency varying loads that the Sprinter's systems (IC panel watching system voltage telling LINbus-controlled alternator's regulator what to supply) can't keep up (or gets into "fatal oscillations")

I'd also put an oscilloscope on the Sprinter-side of the inverter just to see what's happening.
(i should do that on mine, too...) Is your inverter "pure sine wave" or just MSW?

--dick
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2005 T1N 118" Freightliner 2500 Passenger Wagon (2.7L, 15" tires, standard (short) roof)
Get YOUR Sprinter's full configuration datacard by entering your VIN to https://www.datamb.com/
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
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Old 06-15-2019, 09:19 PM   #75
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Thanks for your offered advice.
To clarify:
It’s a 6 cylinder 3.0L
No intelligent battery system (option available in 2014 I think?)

The VIN indicates that:
14 V/220 A ALTERNATOR
ENGINE OM 642 DE 30 LA 115 KW (156 HP) 3800 RPM

The output at the alternator is intermittent... one day it puts 14.1V and the next day 11.9V,

Wondering if replacing the Y-cable the alternator was working overtime and is wearing out?
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Old 06-16-2019, 03:47 AM   #76
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Where was the alternator sourced from?
Dennis
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Old 06-17-2019, 03:28 PM   #77
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Quote:
Originally Posted by will902 View Post
Thanks for your offered advice.
To clarify:
Itís a 6 cylinder 3.0L
No intelligent battery system (option available in 2014 I think?)

The VIN indicates that:
14 V/220 A ALTERNATOR
ENGINE OM 642 DE 30 LA 115 KW (156 HP) 3800 RPM

The output at the alternator is intermittent... one day it puts 14.1V and the next day 11.9V,

Wondering if replacing the Y-cable the alternator was working overtime and is wearing out?
But the NCV3 alternator size/type needs to be the same as the OEM. The T1N could easily swap in a larger alternator. From all that I have gleaned/recall the NCV3 needs to remain as OEM.

Is there any evidence of oil leakage/contamination in the area of the alternator? Oil on the collector rings can result in intermittent brush contact which will affect excitation/output.

vic
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Old 06-17-2019, 04:10 PM   #78
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

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Originally Posted by Aqua Puttana View Post
But the NCV3 alternator size/type needs to be the same as the OEM. The T1N could easily swap in a larger alternator. From all that I have gleaned/recall the NCV3 needs to remain as OEM.

Is there any evidence of oil leakage/contamination in the area of the alternator? Oil on the collector rings can result in intermittent brush contact which will affect excitation/output.

vic
Oh that could be... thanks for the suggestion. Th last time I replaced the engine oil I incorrectly seated the oil filter cap gasket and had oil come up through the cap and spray the under hood. Iíve been monitoring the alternator and it seems to be working correctly for the past 4-5 days.

Would a shop be able to diagnose a bad alternator if the brushes were intermittently losing contact?
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Old 06-17-2019, 04:46 PM   #79
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

It seems unlikely that both the orignal and replacement unit are both bad. Alternator output on the NCV3 is controlled via CANbus (acutally LIN bus) so the replacement must be correct for your vehicle. As Dennis and Vic are hinting, where did you get the replacement unit and are you sure that it is the correct item? And is it an OEM/Bosch replacement or an off-brand?

.

Last edited by smiller; 06-17-2019 at 04:49 PM.
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Old 06-17-2019, 05:26 PM   #80
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Default Re: Autopsy: Infamous "Y" cable from alternator to starter to battery

Quote:
Originally Posted by will902 View Post
The output at the alternator is intermittent... one day it puts 14.1V and the next day 11.9V,
11.9 is *really low* ... if your battery was "normal" (say 12.5 v after engine off for a while), i'd hope it would still be noticeably above 12v if the alternator wasn't helping (unless it's been an hour of "not helping"). The alternator/regulator could be doing other "funny" things.

Bad ground strap connections between alternator/engine and frame, or bad negative to the battery should also be checked, as well as the famous Y cable.

--dick
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2005 T1N 118" Freightliner 2500 Passenger Wagon (2.7L, 15" tires, standard (short) roof)
Get YOUR Sprinter's full configuration datacard by entering your VIN to https://www.datamb.com/
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
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charging, electrical problem, low voltage

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