Alternator issues

[Red-Dv]

Hello
I have two 2001 1.9 tdi engines in a sailing catamaran. I am have issues with the alternators. Neither seems to be producing power. I have and understand that the wiring is not as would be in a car. But i am trying to resolve some issues. I'm trying to determine if i have bad ecm units or bad alternators. My question is should the exciter power for the alternators be coming from the ecm unit or a separate fused line. Second questions is how can i test the ecm unit.

 

[Mozambiquer]

The alternators used on the alh engines are not ecm controlled, they only need power on the one wire going in to the alternator, the exciter wire. (And obviously the main battery wire) The other wire that goes to the ecm is the dfm (field monitor) and it tells the ecm what load the alternator is putting out.
With the ignition on, you should have battery voltage at the blue wire to the alternator, and obviously at the main battery wire.
If you do, and it's still not charging, I'd say you probably have failed alternators. Most often what I see are brushes and slip rings worn out. Both are replaceable, though the slip rings are a bit of a challenge without the correct tools.

 

[oilhammer]

Are these engines VAG marine engines or something custom built? VAG marine engines will have their own wire harness and diagram, but you may also have something for the boat manufacturer themselves. I'd want to see how it is wired up before condemning both alternators. And we (TDI club) cannot help you with that. RingPower was the local importer and parts source for VAG marine engines.

 

[Red-Dv]

Are these engines VAG marine engines or something custom built? VAG marine engines will have their own wire harness and diagram, but you may also have something for the boat manufacturer themselves. I'd want to see how it is wired up before condemning both alternators. And we (TDI club) cannot help you with that. RingPower was the local importer and parts source for VAG marine engines.

No these are not VAG motors marine engines they are regular car engines that were put into the boat to them to catamaran that’s what I’m probably having most of my issues with this

 

[Nevada_TDI]

Hello
I have two 2001 1.9 tdi engines in a sailing catamaran. I am have issues with the alternators. Neither seems to be producing power. I have and understand that the wiring is not as would be in a car. But i am trying to resolve some issues. I'm trying to determine if i have bad ecm units or bad alternators. My question is should the exciter power for the alternators be coming from the ecm unit or a separate fused line. Second questions is how can i test the ecm unit.

When you find the fix, will you please send pictures?

 

[Red-Dv]

The alternators used on the alh engines are not ecm controlled, they only need power on the one wire going in to the alternator, the exciter wire. (And obviously the main battery wire) The other wire that goes to the ecm is the dfm (field monitor) and it tells the ecm what load the alternator is putting out.
With the ignition on, you should have battery voltage at the blue wire to the alternator, and obviously at the main battery wire.
If you do, and it's still not charging, I'd say you probably have failed alternators. Most often what I see are brushes and slip rings worn out. Both are replaceable, though the slip rings are a bit of a challenge without the correct tools.

I appreciate the information that does explain some of the issues. but I don't understand why it would have worked when i first bought the boat about a year ago. this blue wire has not been connected to anything. I have replaced the alternators and am sure they are good.
What im trying to do now is figure out how to wire this correctly.

 

[Nevada_TDI]

Have you thought about going old school and use external regulators?
You could set the voltage you want to feed the exciter wire.
These do not seem to be adjustable in any way, but here is an idea:https://www.amazon.com/Goodeal-Elec...dp/B073XJNCWY/ref=psdc_15719901_t1_B07Z816LR9

EDIT: it is easy to remove and bypass the factory regulator and use an external regulator. This may not be your first choice of solution, but it should help to eliminate some of the variables.

 

[Mozambiquer]

Have you thought about going old school and use external regulators?
You could set the voltage you want to feed the exciter wire.
These do not seem to be adjustable in any way, but here is an idea:https://www.amazon.com/Goodeal-Elec...dp/B073XJNCWY/ref=psdc_15719901_t1_B07Z816LR9

EDIT: it is easy to remove and bypass the factory regulator and use an external regulator. This may not be your first choice of solution, but it should help to eliminate some of the variables.

Doing that would be fairly easy, using the brush holder for a dodge with the Bosch alternator, it'll bolt right on the VW unit, and I've gotten an external regulator for conversions. I can also get one that will make it one wire, no need for an activation wire, all with oem Bosch parts.

 

[JimInPB]

I have a Jetta with a charging problem & am running into a similar issue. The blue wire has no voltage, but when I put voltage to the post where the blue wire goes, the alternator still does not charge. The battery light has never worked, but the car charged for years. I am wondering if the blue wire is really needed to excite the alternator. Since my light never came on, I'm wondering if the blue wire never had power. I'm wondering if the blue wire is just there to light the dash light & warn you of a charging problem, but does not actually cause charging. I would love to find some authoritative information on that detail. It looks like that "bulb" (actually an LED) is not easy to change.

Also, I do a fair amount of fooling around with sailboats. I'm curious how the cat guy in Key Largo made out. I'm just a couple of hours from there.

Edit:
A test light (incandescent bulb type) does not show voltage at the blue wire when the key is on with motor off, but a digital volt meter does show 12vdc there. The battery light on my dash still does not come on when the test light is put on the blue wire with the key on & motor off.

 

[JimInPB]

Can anyone point me to a diagram that shows the blue wire feeding signal power to the alternator?

 

[Mozambiquer]

Here's the wiring diagram that shows the wiring of the alternator. It shows power coming from fuse 11, going through the LED on the instrument cluster, then going to the alternator.
If that is grounded, it should light up the charge light. I'd look at fuse 11 and go from there.

Can anyone point me to a diagram that shows the blue wire feeding signal power to the alternator?

 

[JimInPB]

View attachment 117904
Here's the wiring diagram that shows the wiring of the alternator. It shows power coming from fuse 11, going through the LED on the instrument cluster, then going to the alternator.
If that is grounded, it should light up the charge light. I'd look at fuse 11 and go from there.

Thank you for the drawing. That is a huge step forward for me. My test light glows bright on both sides of fuse 11, so I'm good there. I guess that the next step is to find connector T32 & check for voltage at pins 1 & 12. I'm going to assume that I'll have to pull the cluster for that.

 

[Mozambiquer]

Thank you for the drawing. That is a huge step forward for me. My test light glows bright on both sides of fuse 11, so I'm good there. I guess that the next step is to find connector T32 & check for voltage at pins 1 & 12. I'm going to assume that I'll have to pull the cluster for that.

Did you check at the plug above the starter? I don't think it needs to carry a load, as it's passing through the LED on the dash. It should just show 12 volts with key on.

 

[JimInPB]

I found the same story at the plug above the starter. It would read 12v with a DVM but it would not make my test light glow. The new alternator is in & working normally. That means one of two things. Either that wire is really just going to an idiot light & not needed to make the alternator charge, or else it takes very little current to start the alternator charging. There is enough leakage current in the system to read on a meter, but not enough to light a bulb. My idiot light is not working. For now, I have an aftermarket indicator plugged into the cigarette lighter, so I'll just have to rely on that for my charge system indicator.