alternator confusion

[njl]

I'm trying to fix the alternator wiring on my Volvo Penta md11c - it hasn't been working since I bought the boat, and I've been recharging my batteries with shore power. The alternator should be charging two 80Ah Sears DieHard deep cycle wet cell batteries.

The alternator is a Delco 63 amp alternator (#1103091) with built in regulator that was wired to something called an Automac alternator controller. I believe the Automac fakes out the voltage sensor on the alternator in order to charge the batteries at a faster rate.

The alternator was connected to the automac via two wires, a 4-guage cable connected to the "bat" terminal on the alternator, and another 12 awg wire that mysteriously comes out of the alternator between the terminal posts labelled 1 & 2. There was nothing connected to 1 & 2 previously. The 12 awg wire was connected to the on/off switch on the Automac, but I believe also gets fed a variable voltage based on a dial you can turn on the Automac.

According to the former owner, the current wiring set up was initially working, but became finicky and then stopped all together at some point. Today, I removed the Automac and tried connecting the alternator directly to the battery, but wasn't sure what to connect the sensor wire to. So I tried to leave the sensor wire unconnected, but the alternator didn't produce any charge. (Should it?)

I then tried to get the alternator tested at PepBoys, but the technician couldn't figure out how to work the testing machine they have.

Tomorrow, I plan to reinstall it and wire the sensor to the ignition key switch and see if that makes a difference. If not, I have a "spare" alternator (possibly also broken) that I will try in the same way. If those both fail, then I'll try to find another auto shop that can test the alternator.

Could anyone with experience in this sort of thing tell me if I'm on the right track or way off base? Also, should I be concerned that there is no ground on the alternator?

 

[anchorclanker]

When an employee of an auto store doesnt know how to test a Delco alternator, you need to go to a different store. You already have it out, it would be unwise not to test it. Then check the wiring, its possibly wired wrong and failed because of it.

 

[sailaway78]

Find you another store

Find yourself another auto supply, or better yet, an alternator shop.

 

[alexco38]

That is not a sensor wire. Don't hook it to the ignition switch. It'll blow the regulator.

There are 4 terminals on a alternator for a diesel engine:

(1) B+ goes to the battery terminal or combiner diodes. Never to a A-B switch.
(2) W goes to the tachometer because diesel don't have ignition pulses
(3) 61 is the Alt fault light on the instrument panel. It provides exciter voltage to get charging started.
(4) B- is the ground should be connected to the engine ground. Don't count on the mounting to ground the alternator. It may have resistance.

If the Prepboy guy can't operate the machine, go somewhere else. Better find a local automotive electric shop. They know what they are doing. Prepboy is just a retailer.

 

[njl]

I ended up just buying a new alternator which I just wired in according to an engine diagram in my Volvo Penta manual and everything seems to be working at the moment.

One of the things I did was to connect the #2 (sensor) wire to the Batt terminal post as suggested at the following link: http://www.hartin.com/alternator.htm. Is this a bad idea?

Also, my engine manual's wiring diagram states that the alternator Bat terminal should connect to the starter which feeds through to the battery. Since Alexco38 says I should be connecting that directly to the battery, I don't know which advice to follow.

Should any of these wires be fused? I'm using the wires that came with the engine which is from the 80s. Not sure if best practice has changed since then.

Thanks for any replies!

 

[heritage]

It shouldn't be a problem either way. By connecting directly to the starter, you can get by with a shorter wire with less possibility of chafing. You are simply using the starter stud as a connection point to the battery.

If you have an on/off switch between the starter and starter battery, then there is the possibility that you could fry the alternator by turning the switch to off while the engine is running. If you have a starter switch, then it would be prudent to run the B+ wire directly to the start battery.

 

[Stu Jackson]

Are you fully conversant with boat wiring and switching for alternator outputs (AO)?

The choice between wiring the AO direct to the house bank vs. to the boat's 1-2-B switch C post and linking the AO to the starter and then to the C post is a really basic choice you have to make and understand.

Here's why and also some design choices you have.

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html [added 9/21/11]

[added 1/31/2012] This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

You'll also have to determine where you run your sense wire, best to the house bank.

Here's what I did with mine, but you have an internal regulator. http://c34.org/bbs/index.php/topic,4548.0.html

I suggest you do before (if you can, now) and after wiring diagrams and at least do the after diagram before you install anything.

There's a really neat "Alternator Handbook" PDF floating around the internet, if I find a link I'll let you know.

OK, here it is: see the link below.

Good luck.

 

[njl]

Thanks for all the information! I'll read through and see if I should make adjustments.