New Alternator Question

[Levinz11]

My boat was running very rough, intermittently, the last few trips out. All would be fine for 30 mins or so then it would start bogging and not getting any revs going. So I did a full tune up per the FSM. Went out again and it ran well for 10 mins then dies and wouldn't start. Check voltage and had 9 at the battery. Charged it up and when running only had 11 or so volts. I bought a new alternator and installed it.

So my questions is.....Now I have 15.5 volts at the battery while the engine is running. Is that OK?? Seems high.

The battery is 2 months old.

Thanks

 

[Levinz11]

Re: New Alternator Question

This is the alternator I ordered. http://www.amazon.com/gp/product/B00027GZ7S/ref=oh_details_o01_s00_i00 The actual model I received is Mando 51 amps.

Am I frying my battery?

 

[Levinz11]

Re: New Alternator Question

Also the PO put this wire from the B+ post on the alternator straight to the battery. The regular orange harness wire is also attached to the same post.

 

[bruceb58]

Re: New Alternator Question

B+ is the ouput of the alternator. Its fine for it to go to the battery terminal. It sure doesn't look like a big enough wire though. I take it the original orange wire stiil goes down to the starter? If that's the case, the two wires are essentially in parallel.

Did you measure the voltage with a meter?

 

[Levinz11]

Re: New Alternator Question

B+ is the ouput of the alternator. Its fine for it to go to the battery terminal. It sure doesn't look like a big enough wire though. I take it the original orange wire stiil goes down to the starter? If that's the case, the two wires are essentially in parallel.

Did you measure the voltage with a meter?

Yes, sir used a multimeter. The dash gauge still shows 12.1 - 12.5 volts while running. But with my meter at the battery while running I'm getting 15.5. Not running I'm getting 12.8 ish. Do you think the external regulator on the alt. is bad?

 

[bruceb58]

Re: New Alternator Question

The alternator should have an internal regulator. Or maybe yours and my definition of an external regulator are different.

15.5 is too high.

There should be a sense terminal on the alternator. How is it wired?

 

[Don S]

Re: New Alternator Question

Yes, 15 volts will damage your batteries, you would be boiling the water out of them.
Please answer all three questions below.

1. Would you please post a picture of the back of the alternator you received?

2. Is the orange wire from the alternator hooked up to the starter?

3. Are purple and the red/purple wires hooked to the correct terminals of the starter?

 

[Levinz11]

Re: New Alternator Question

The alternator should have an internal regulator. Or maybe yours and my definition of an external regulator are different.

15.5 is too high.

There should be a sense terminal on the alternator. How is it wired?

Yea, the regulator is internal on the alt. My bad.

Purple wire to Sense post. Red w/purple stripe to exciter.

I just read this on a car forum...
"I solved the problem. I have a 3 wire alternator and had connected the main post to the battery and the two oem wires to the pigtail. Technically it was wired correctly. I read something tonight on another forum about being able to boost the voltage output of a alternator by putting a resistor inline with the exciter. So I got to thinking and previously when I testing some wires in the cab for a keyed on power source there was a volt drop. I am not sure if I just have a dirty ignition or what. So since the alternators eciter was triggered by the key on it basically had the resistance inline and wasn't truely sensing the battery voltage.

I just clipped my eciter wire and tied it off and did like others have done by just connecting the exciter straight to the main output terminal effectively making it a one wire style alternator. Fired up the engine and got my 14.5 volts. Stayed nice and constance with accesories turned on too where the other way would jump a half volt or so. Problem solved. "

Maybe I'll try that tomorrow.

 

[Don S]

Re: New Alternator Question

That resistor trick is what is used to up the output when using a battery isolator when charging two batteries. The isolators are made with diodes that take almost a volt to operate. To get that volt back you use the resistor.

 

[Levinz11]

Re: New Alternator Question

That resistor trick is what is used to up the output when using a battery isolator when charging two batteries. The isolators are made with diodes that take almost a volt to operate. To get that volt back you use the resistor.

Well I'm at a loss then. Guess I'll run her this weekend and keep checking battery temp, voltage and water level....and see what happens. The new alt is wired up according to the FSM and just like the old one was.

My dash gauge showing 12v while running means its useless and I guess I got a rebuilt alternator that is simply putting out too much juice.

 

[bruceb58]

Re: New Alternator Question

Just for a sanity check, can you measure the voltage at the sense and excitor terminals while the engine is running? They all should be the same as the alternator output.

Your 12V at the dash is worisome to me. That is also where the sense voltage is coming from so maybe you have a bad connection somewhere. It sounds like a similar issue that you read on that car forum. I wouldn't do what they suggested though.

If the voltage measures low, time to track down where the voltage drop is. Could be a bad ignition switch or engine main connector.

 

[Levinz11]

Re: New Alternator Question

Yes, 15 volts will damage your batteries, you would be boiling the water out of them.
Please answer all three questions below.

1. Would you please post a picture of the back of the alternator you received?

2. Is the orange wire from the alternator hooked up to the starter?

3. Are purple and the red/purple wires hooked to the correct terminals of the starter?

This is the alternator I received.

I'll have to check where the orange wire goes. To be honest I never followed it back.

FSM says purple lead to "S" terminal, red w/purple stripe to "ecs" terminal....which if you'll notice is backwards from how you receive the alternator.

 

[Levinz11]

Re: New Alternator Question

Just for a sanity check, can you measure the voltage at the sense and excitor terminals while the engine is running? They all should be the same as the alternator output.

Your 12V at the dash is worisome to me. That is also where the sense voltage is coming from so maybe you have a bad connection somewhere. It sounds like a similar issue that you read on that car forum. I wouldn't do what they suggested though.

If the voltage measures low, time to track down where the voltage drop is. Could be a bad ignition switch or engine main connector.

Bruce, I'll get on this recommendation when I'm home from work tonight and report back. The dash gauge is bugging me too.

 

[bruceb58]

Re: New Alternator Question

FSM says purple lead to "S" terminal, red w/purple stripe to "ecs" terminal....which if you'll notice is backwards from how you receive the alternator.

Which doesn't really matter since they are connected together eventually anyway.

 

[Don S]

Re: New Alternator Question

FSM says purple lead to "S" terminal, red w/purple stripe to "ecs" terminal....which if you'll notice is backwards from how you receive the alternator.

The red and the purple wires shown in your picture are in the correct location. What FSM do you have? Is it Seloc or Clymers?

Here is how Volvo wired that alternator.

 

[Levinz11]

Re: New Alternator Question

Here is a screen shot from the manual i am using. I found it on this board. I thought it was the factory manual.

 

[Levinz11]

Re: New Alternator Question

The red and the purple wires shown in your picture are in the correct location. What FSM do you have? Is it Seloc or Clymers?

Here is how Volvo wired that alternator.

View attachment 152325

Hmmm.....maybe i just need to switch the wires around then. Because that picture you posted Don is exactly the opposite of what my manual says to do.

 

[Don S]

Re: New Alternator Question

Yes, you need to switch them. That looks like an OEM manual, but don't forget, manuals do have errors in them, and dealers get service bulletins and changes about errors in manuals. But not all manuals are owned by dealers so they don't get the updates and changes.

 

[bruceb58]

Re: New Alternator Question

My Cobra factory manual shows the two wires joining each other in the harness. I also have a Volvo "LK" manual that shows the EXC and Sense wire joined on the alternator and one wire going back to the ignition switch.

There is definitely no reason to not have the sense line on the output as shown in DonS's picture. In fact, that is a way better place to sense the voltage. If you wanted to be more precise you would have it on the battery to account for voltage drops in the orange wire.

Only the EXC wire really needs to be switched.

 

[Levinz11]

Re: New Alternator Question

My Cobra factory manual shows the two wires joining each other in the harness. I also have a Volvo "LK" manual that shows the EXC and Sense wire joined on the alternator and one wire going back to the ignition switch.

There is definitely no reason to not have the sense line on the output as shown in DonS's picture. In fact, that is a way better place to sense the voltage. If you wanted to be more precise you would have it on the battery to account for voltage drops in the orange wire.

Only the EXC wire really needs to be switched.

So I couldn't do anything last night due to rain. Tonight however I am going to switch up the wires. Soooo if I have this straight I am going to connect :

-Red w/purple stripe ton "S"-Sense
-Purple to EXC-Exciter
-Orange to B+

I don't have as many wires as Don's pic shows. Let me know if I got it right.