Help with alarm and alternator

[Zink357]

I have a 2010 Volvo penta 4.3GL serial# A104925. product# 3869391. After having the intake manifold off and doing some work, put it all back together and the alarm is going off nonstop. Not a beep but continuous alarm while running. I pulled off the leads to the exhaust temp sensors, the oil pressure sensor, and the engine temp sensor and still have the alarm. Only way I can stop it is to pull the brown lead off the back of the alternator. I’m curious what that alternator lead if for and what voltage it should have while running. I’m only getting about 7.5v from it and wondering if it should be 12v? My next test will be to check for continuity to ground on those four sensor leads next time I get to it. Anyone know what I can do to figure this out? Also, anyone tell me what the brown lead on back of the alternator is for and what voltage I should have there? I’m assuming it goes to the ignition switch but not sure. Thank you for any help you can give me!

 

[alldodge]

Only way I can stop it is to pull the brown lead off the back of the alternator.

You sure it's Brown and not Purple?
Finding GL-J

Pulling the intake off check that the Tan/Black wire was not pinched some where. You should see 12V from the ALT Purple wire

 

[Zink357]

You sure it's Brown and not Purple?
Finding GL-J

Pulling the intake off check that the Tan/Black wire was not pinched some where. You should see 12V from the ALT Purple wire

Here’s a pic. White arrow is the brown wire I was talking about. It’s actually brown with black stripe. Maybe the tan/black you’re talking about?? Purple arrow is the green and purple wires coming from the alternator. Not seeing any wires pinched anywhere.

 

[alldodge]

I don't have the GL-J, only up to E model. On the ones I have the ALT feeds power to one side of the alarm and the Tan/Black is used to apply ground to turn alarm ON when one of the sensors is activated.

Your ALT having the wire attached to the ALT now, might mean that ALT now applies a ground also to advise when its not working correctly. With the motor running the main output post should show 14+V

 

[Zink357]

I don't have the GL-J, only up to E model. On the ones I have the ALT feeds power to one side of the alarm and the Tan/Black is used to apply ground to turn alarm ON when one of the sensors is activated.

Your ALT having the wire attached to the ALT now, might mean that ALT now applies a ground also to advise when its not working correctly. With the motor running the main output post should show 14+V

So do you think the alternator is possibly bad? Or is there another possible problem?

 

[alldodge]

So do you think the alternator is possibly bad? Or is there another possible problem?

That is a Maybe
Measure the output voltage to verify the voltage is 14 to 14.7V
The measurement should be after the motor revs at least once to about 1500 rpm. If before the first rev increase it may read lower. Many motors auto rev and then come back down after start

 

[dwco5051]

Don't know about your motor or wiring but things have changed since I was a kid. My truck controls the solid state regulator in the alternator by a signal from the powertrain control module (PCM) That signal comes from the PCM as a clipped signal and the charging rate is controlled by the frequency of the signal. Normal operation for my unit is around 7.5 volts on the signal wire.

As others have said check your voltage on your battery with the motor off and then when running. 12.8 off 14 or so running means no problem with the alternator.

 

[Zink357]

I don't have the GL-J, only up to E model. On the ones I have the ALT feeds power to one side of the alarm and the Tan/Black is used to apply ground to turn alarm ON when one of the sensors is activated.

Your ALT having the wire attached to the ALT now, might mean that ALT now applies a ground also to advise when its not working correctly. With the motor running the main output post should show 14+V

My motor is a GL-J? How do you tell that? I assumed it was GL-A because of the A in the serial number...

 

[alldodge]

Can look your serial number up on this link
https://www.volvopentashop.com/epc/en-US

In top left select Orange color "apply filters"
The drop down put in the serial number

 

[Zink357]

Awesome. Thank you!

 

[Zink357]

Checked all the leads for continuity to ground and the only one showing ground is the wire to the water temp sensor. I don’t see anywhere that it got pinched or damaged in any way. What’s my next step to finding the problem?

 

[alldodge]

That is a Maybe
Measure the output voltage to verify the voltage is 14 to 14.7V
The measurement should be after the motor revs at least once to about 1500 rpm. If before the first rev increase it may read lower. Many motors auto rev and then come back down after start

Has the output been measured?