terminals D+ B+
- Thread starter robbieG
- Start date
mean_in_green
>2,000,000m in MB vans
It's a connectivity protocol, although the use of the word "terminal" is a bit misleading as it refers to an element of the vehicle wiring design rather than a specific connection point. These "connections" can have complex logic assigned to them.
I think D+ is the signal for the battery charging circuit, and I'm pretty sure B+ is the output signal from the alternator. There are loads but I don't have a list of them. Another common one is Terminal 15: ignition on, but remember - it's could be more complicated than that according to what the manufacturer needs it to do, so for example it could mean:
"Ignition on and 12v there as long as the voltage at some other place does not fall below a predetermined value or switch this other thing also connected and do that other operation after that but not if the vehicle lights are on and the radio is tuned Classic FM!" *
* I may have made some of that up but you see how it works...
I think D+ is the signal for the battery charging circuit, and I'm pretty sure B+ is the output signal from the alternator. There are loads but I don't have a list of them. Another common one is Terminal 15: ignition on, but remember - it's could be more complicated than that according to what the manufacturer needs it to do, so for example it could mean:
"Ignition on and 12v there as long as the voltage at some other place does not fall below a predetermined value or switch this other thing also connected and do that other operation after that but not if the vehicle lights are on and the radio is tuned Classic FM!" *
* I may have made some of that up but you see how it works...
Eric Experience
Well-known member
RobieG
The vehicle is fitted with 3 terminals that are called " body builders connnections" Thes are provided so you can get 1 direct battery, 2 ignition on , and 3 power when engine is running that is D+. These terminals are under the drivers seat in a black plastic block about the size of a match box, it is placed near the handbrake lever. The intention of 2+3 is for you to use these terminals to control relays for any functions you may wish to add. Eric
The vehicle is fitted with 3 terminals that are called " body builders connnections" Thes are provided so you can get 1 direct battery, 2 ignition on , and 3 power when engine is running that is D+. These terminals are under the drivers seat in a black plastic block about the size of a match box, it is placed near the handbrake lever. The intention of 2+3 is for you to use these terminals to control relays for any functions you may wish to add. Eric
From the service manual:
The generator provides a hard wired input to the instrument cluster circuitry on the engine running (D+) circuit. If the instrument cluster turns on the indicator while the engine is running, it may indicate that the charging system requires service. The generator input circuit to the instrument cluster can be diagnosed using conventional diagnostic tools and methods.
There is also a D+ Relay 1 and D+ Relay 2.
Bruce
The generator provides a hard wired input to the instrument cluster circuitry on the engine running (D+) circuit. If the instrument cluster turns on the indicator while the engine is running, it may indicate that the charging system requires service. The generator input circuit to the instrument cluster can be diagnosed using conventional diagnostic tools and methods.
There is also a D+ Relay 1 and D+ Relay 2.
Bruce
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autostaretx
Erratic Member
B+ is raw battery power ... usually though a fuse in the Sprinter.
They actually label dozens of points "fused B+", but one source is fuse 3 on the T1N power distribution (PDC) fuse block mounted on the positive battery post. Many of the other "B+" may have passed through more than one fuse, but they're still unswitched.
D+ is "switched" power... in the T1N Sprinter, "D+ Relay One" is pulled in by a signal from the Instrument Cluster.
D+ Relay One then pulls in D+ Relay Two, for additional switched current capacity.
The B+ that the D+ relay switches arises from PDC Fuse 3.
D+ can be thought of as "alternator up and charging"... among the secondary relays that D+ Relay One pulls in are the Daytime Running Lights (DRL) and the MB-installed "isolator" relay which connects the Auxiliary battery to the alternator for on-the-road charging.
In Ye Olden Days, the B+ and D+ were labeled terminals on generators/alternators.
There's a third feed of interest, the "Run-Start" circuit. It's active when the ignition switch is in the "run" position.
(there's also the 4th "accessories" circuit), but i don't think either of those has a "one letter" tag like B+ and D+.
If you have any T1N service manual, you can trace the "B+" and "D+" names in the connector pinouts listings.
They're not frequently labeled on the circuit schematics themselves.
--dick
cedarsanctum
re: Member
Here's a nifty little pdf that shows the EK1 terminal under the seats of most NCV3, and i think T1N's, and what they do.
View attachment EK1 Body Builder electr.pdf
Hope this helps
Jef
View attachment EK1 Body Builder electr.pdf
Hope this helps
Jef
Colorado_Al
Well-known member
This is the info you need, specific to the Bosch alternator (which is used in the Sprinter)
http://www.pelicanparts.com/techarticles/914_alternator_troubleshoot/914_alternator_troubleshoot.htm
https://sprinter-source.com/forums/showpost.php?p=115919&postcount=8
shortshort
Dis member
A lot. People ask for that all the time. I'd seen it, but was unable to relocate it.
Thank you all so much for this information! I have done so much work on my 2006140" T1N because of this forum! I am currently installing a bird's eye camera system and am so glad I came across this ek1/terminal d+ under the druver's seat.
The bird's eye system connector has 3 wires though. One for batt+, GND, and another for ACC ON connector. Would this mean that I would connect the batt+ to the "hot" 25 amp fused battery power terminal, and the connect the ACC ON wire to the ignition on terminal?
Sorry, I am not very electrical savvy, but am learning very quickly!
- Stan
The bird's eye system connector has 3 wires though. One for batt+, GND, and another for ACC ON connector. Would this mean that I would connect the batt+ to the "hot" 25 amp fused battery power terminal, and the connect the ACC ON wire to the ignition on terminal?
Sorry, I am not very electrical savvy, but am learning very quickly!
- Stan
Nautamaran
2004 140” HRC 2500 (Crewed)
Best practice would be to run a dedicated circuit, yes.
That said, convenience plays a roll too, and for such a small load be aware that there is fused B+ power available at the dome lamps, and switched power at the radio antenna. The dome lamps share a fuse with the radio, so if you mess up the effects will be isolated to those circuits. Each dome lamp has two grounds, one direct and one switched.
So you could safely tap either of these sources to power your display (or even use the antenna power to trigger a relay that switches the B+ power on/off and eliminates any parasitic drain).
Or you could run dedicated wiring from under the seat, routing it forward through the floor tunnel, up through the dash, and up the A-pillar by the windshield.
Their is also a factory ground lug (G301) located in the upper right rear corner of the van that may be convenient for grounding your camera.
-dave
That said, convenience plays a roll too, and for such a small load be aware that there is fused B+ power available at the dome lamps, and switched power at the radio antenna. The dome lamps share a fuse with the radio, so if you mess up the effects will be isolated to those circuits. Each dome lamp has two grounds, one direct and one switched.
So you could safely tap either of these sources to power your display (or even use the antenna power to trigger a relay that switches the B+ power on/off and eliminates any parasitic drain).
Or you could run dedicated wiring from under the seat, routing it forward through the floor tunnel, up through the dash, and up the A-pillar by the windshield.
Their is also a factory ground lug (G301) located in the upper right rear corner of the van that may be convenient for grounding your camera.
-dave
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