Alternator issues

Red-Dv

Member
Joined
Apr 2, 2019
Location
Key Largo
TDI
2001
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

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta TDI
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

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis (where it's safe)
TDI
There are just too many to list....
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

Member
Joined
Apr 2, 2019
Location
Key Largo
TDI
2001
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

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta 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

Member
Joined
Apr 2, 2019
Location
Key Largo
TDI
2001
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

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta 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.
 
Last edited:

Mozambiquer

Vendor , w/Business number
Joined
Mar 21, 2015
Location
Versailles Missouri
TDI
1998 VW Jetta TDI. 1982 VW Rabbit pickup, 2001 VW Jetta 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.
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.
 
Top