gsrhach

Just a topic to throw up in here . How many of you guys know that the alternator/voltage regulator is also tied into the ABS system . Voltage regulator not working right ABS may not be kicking on .
Topic comes from a recent 96 integra i was working on. The altenator was charging @ 14.7 volts when the white wire (from the alternator to the under hood fuse block) was off the fuse block. But when under load i.e. connected to the fuse block . That same wire was only showing a read out of 11.9 to 12.3 volts .
Has anyone else had this type of problem between the charging system and the ABS system?

gsrhach

no one nothin?

forced4gsix3

Mess with a modern day CAN BUS system and see what voltage irregularities can do. It's not uncommon for low voltage to mess with other computer controlled systems.

Fabrik8

So what were you having a problem with, the voltage regulator or the ABS system? If you're having voltage regulator problems, you can swamp tons of different things with noise. That includes sensors, communication, all kinds of stuff.

CAN communication isn't going to be disrupted by 11V in the slightest. Most automotive electronics are rated for operation down to 8 or 9VDC, CAN communication included. Nasty amounts of EMF from a bad voltage regulator is a different story though, because even small amounts of bad data from signal disruption can cause faults with safety critical systems.

So I don't think that the low voltage is the problem, but the byproduct of what is making the voltage low is probably what's killing you.

Most of the low voltage computer disruption problems aren't caused by the voltage but the cause of the low voltage. If you have a weak battery for example, and you try to crank the engine, the current draw can be more than enough to almost instantaneously drop the system voltage way out of the range of what the electronics can handle, and it only takes a very fast transient to reset the ECU, etc. Same with problems like bad grounds, anytime you have a problem delivering enough current for everything than you can have problems like that. If you're sitting at 10V, and you turn the fuel pump or fan or something on, and it briefly draws 3 to 5 times the normal operating current during turn-on, you only need to drop the voltage about 2 more volts for just an instant to get out of the rated range of just about all automotive electronics and cause a reset. That's easy if you have a weak battery, bad ground, etc that can't easily supply the necessary current.

gsrhach

The problem . Car is draining the battery . Example fresh fully charged good battery in car .Drive for a while and it gets drained enough to kill the car . Also the abs system won't turn on period the light just stays on on the dash . and i cant pull the codes doing the jumper on the plug . well while trouble shooting after a new alternator was put in of why the battery was still getting drained. There is a test to ground one of the wires (white with blue if i remember correctly ) on the plug to the alternator and the ABS system kicked on and worked . AMAZING because i have not seen the system work since working on the car . the abs light on the dash just stays on . Well if you have the car runing and test the alternator at the terminal on top of the alternator with the wire pulled off of the fuse block . The wire coming from the alternator . You get 15 v but if you connect the wire to the fuse block . its like the alternator stops producing opwer .The only reading you get is 11.5 to 12 volts so i am assuming the current is just coming from the battery at that point.
I am working with a wiring diagram and all of that . On the diagram is a wire that comes fom the alternator and goes to the battery light and the ABS control unit . So once again i am under the impression that the alternator and the ABS control unit issues are connected . I'm not a Noob, just havent experienced this problem before. I have a ASE tech helping me try and trouble shoot this and figure out the problem . And will be keeping this thread posted on what i find out . Just in case someone else experiences this problem .I cant get back to my garage til friday evening . I usually open up shop friday evening and saturday and sunday . Due to my full time job . Also may take pictures to accomidate this thread . so anyone that may want to drop their two cents can see as well as read whats goin on

Fabrik8

Ah, so this is the rest of the story. This is starting to make more sense now.

Sounds like you need to find someone with a current probe and see what the current drain values are when the ABS system is disconnected and connected. I'm not really convinced that the ABS system is the problem, but it shouldn't be that hard to prove or disprove. I think there is a fuse for the ABS system IIRC, so that may prevent you from having to physically disconnect the harness at the ABS module in order to test your theory.

gsrhach

Yes , the rest of the story but i am not disconnecting the ABS control unit . It is one wire one the green plug to the alternator that when grounded kicks on the ABS system . And i am not making a theory i like the way you put it tho . I am trying to figure out why when the White wire to the under hood fusebox is disconnected , the alternator puts out 15+ volts and when it is connected the alternator really isnt even working . I am not sure if it is a faulty voltage regulator in the new alternator , or a wiring issue .
What i was trying to say earlier i did not know that the two componants were directly linked to one another .


what i highlighted on the alternator in green is what measures a 15+ volt reading when the wire i highlighted in red is disconected . When i hook the wire i highlighted in red up to the fusebox it only measures the pull from the battery at these points

Fabrik8

So looking at the wiring diagrams for that car, the ABS system gets power from the battery, just like every other electrical device in the car. There isn't any other connections to the alternator except standard fused power.

Here are the connections on the alternator plug. I'm going off of what they SHOULD be, so if they're not connected properly at the alternator plug (or at the other end) then my description of their behavior may be completely different.

The white/blue wire (pin 3?) on the alt plug is the lamp wire, which turns the charging light on. It can't cause a problem like you're talking about, the regulator grounds the wire to turn the light on and ungrounds it to turn the light off. It goes to the fuse box under the dash.

The white/green wire (pin 2?) is the normal/low charge control from the ECU. The ECU grounds this wire during low load to save gas (less engine load from the alternator). This is probably the wire you're talking about grounding to test the alternator. It goes right to the ECU.

The white/red wire (pin 4?) is the field circuit monitor, and is used by the ECU to monitor when the regulator turns on the field circuit (internally) to make the alternator charge. It goes right to the ECU.

The black/yellow wire (pin 1?) is from the ignition, and supplies power to the regulator assembly. Power has to be there for the alternator to charge.

There is also the ELD wire that goes from the underhood fuse box to the ECU. The big (main power) white wire on the alternator output stud is monitored by the ECU and is part of how the ECU decides to switch charging modes (to low or normal), etc.

Ok, exactly what wire color are you talking about? It's your turn, you need to verify what is where and that everything is connected properly at both ends.

Is this an engine swap by the way?

Fabrik8

You should still disconnect the ABS system and try to track down what it causing the current drain. Who knows, it could be a problem with the voltage regulator, but I'd be really surprised if you had two bad alternators with the same failure mode unless there is a very obvious wiring problem.


Ok, I think I see what is going on now. You're disconnecting the big white wire on the underhood fuse box, which is the same wire attached to the output lug on the alternator. That's why you're seeing a different voltage with it connected to the fuse block versus not connected. The regulator, with no load on it, puts out a higher voltage than with a load applied obviously.

gsrhach

yes it is an engine swap but not to a different car it is a b18b into a gsr body . and all of those wire are hooked up like you are explaining .btw thank you .
i did verify that the wire for the light has no break in it and works when grounded . the problem i think i am having is that the alternator is not turning on when it is needed all of my plugs are clean and connected that was the first thing i checked . all of the fuses are good that was another first before cracking into it . when i get the chance i am goin to back probe the other wires to make sure there isnt any break in them