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SI-ACR Aux battery setup - alternator light issues
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lwillis
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PostPosted: Wed Jul 10, 2019 6:47 am    Post subject: SI-ACR Aux battery setup - alternator light issues Reply with quote

Hello,

Last summer I installed a Blue Sea SI-ACR in order to add a 110 AH deep cycle battery to my van. The setup is simple: SI-ACR between both positive terminals through a 4ga wire, fused both sides of the relay. Fused ground wire from relay to chassis. There is a battery charger connected to the aux battery that ends up charging both batteries though the relay when connected to shore power.

Everything has been going great with this setup. However, as of recently, my alternator warning light stays on when starting the engine. It started slowly: it would stay on but would quickly go off once i very mildly revved the engine. Now, it stays on even when I rev the engine beyond 3000 RPM. It has even stayed on while driving a few times, which is obviously a major problem. I tested the starting battery with the engine running and it does not seem to be getting a charge, as it is below 12.7 volts. Once the light comes off, it does get to 13.6 volts.

This is a fairly recent alternator, roughly 2 ou 3 years old.

Does anyone else have a setup with the SI-ACR? Should I have connected the SI-ACR ground through a relay with the blue alternator wire so that it only joins the battery once the alternator has been "excited"?

Any ideas and/or suggestions would be greatly appreciated!
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PostPosted: Wed Jul 10, 2019 7:19 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

I don't think the ground on your relay will make a difference. I assume you added a wire from the starter to the si acr. You make sure everything is tight around there? Maybe clean the connections there.

Have you tried disconnecting the ground of the si acr to see if the problem still exists? I'd disconnect it, then go to auto parts store and ask to test battery and alternator.
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lwillis
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PostPosted: Wed Jul 10, 2019 7:32 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Thanks for the reply.

Actually, I hooked up the SI-ACR to the positive terminal of the main battery, not to the starter. When doing my research, this seemed to be a setup used by many. Could this be a problem?

When I disconnect the ground from the aux battery, thus disabling the SI-ACR, my alternator light behaves normally...
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PostPosted: Wed Jul 10, 2019 7:52 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Its a relay charge splitter as opposed to a diode type splitter, your batteries have become unbalanced as they are very un similar the current has chosen the easiest route.
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PostPosted: Wed Jul 10, 2019 8:15 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Sounds like most likely an alternator problem.

One test is to start the engine and make sure the warning light stays on.
Then use a piece of wire to momentarily connect the blue wire small stud on the back of the alternator to the red wire large stud. Just a less than 1 second touch. Does the dash warning light turn off?

Either way, now measure the voltage between the red wire stud and the alternator case. Is it over 13.5 volts? What do you get?

Mark
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PostPosted: Wed Jul 10, 2019 8:46 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Pull your regulator and inspect the brushes. I would advise you buy the adjustable regulator from aircooled.net and adjust to get 14.4 at your batteries while charging. Stock is closer to 13.7.

https://vwparts.aircooled.net/Adjustable-Voltage-R...ulator.htm

s
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PostPosted: Wed Jul 10, 2019 9:43 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Thanks so much for the replies!

The van was with my mechanic. After a few tests, he suspects there may be a problem with my instrument cluster, as it has been causing problems with other functions (the oil pressure buzzer, among others). My 14-pin connector is indeed in pretty bad shape. I'll verify the state of the alternator connector once I get the van back...

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Wed Jul 10, 2019 9:45 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

crazyvwvanman wrote:
Sounds like most likely an alternator problem.

One test is to start the engine and make sure the warning light stays on.
Then use a piece of wire to momentarily connect the blue wire small stud on the back of the alternator to the red wire large stud. Just a less than 1 second touch. Does the dash warning light turn off?

Either way, now measure the voltage between the red wire stud and the alternator case. Is it over 13.5 volts? What do you get?

Mark


I'll be trying this as soon as I get the van back. Should the light still stay on, would that mean the blue field wire is disconnected somewhere?
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PostPosted: Wed Jul 10, 2019 11:36 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

General question for the peanut gallery to confirm since I don't have my bentley in front of me: assuming a "stock" Vanagon wiring setup with only a starter battery (no house battery or ACR) the alternator light functionality is an indicator of only charging circuit voltage right? Like if I had a starter battery with dead cells that will never take a charge but have the van running with a good alternator, the charging circuit would have ~14.2V anyway and the alternator light would not be on correct?

Backing up for a second to troubleshoot this specific instance: Having the ACR installed is very useful background and could certainly be related to the root cause for why this is happening, but my guess is that the issue is simpler.

Based on your install info, I can't think of a way the ACR could be a factor in this symptom "right then at the moment" once the engine is running (whether it could have led to premature failure of an alternator component over time is above my pay grade). Follow my logic here and see if I got anything wrong: if everything were working perfectly in your *stock* charging circuit, then your alternator is pumping out some amps to the positive post of the alternator, and that post is connected via a wire to the positive terminal of your starter battery from the factory. From your description your ACR/house battery setup is that you have a wire coming off the positive terminal of the starter battery and going to the positive terminal of the house battery with the ACR in between, correct?

So if that is correct, even if the ACR itself is totally broken or was installed wildly incorrectly, the only possible outcomes would be that the circuit between the positive terminals of your two batteries never connects, is always connected or intermittently connects... I cannot think of any other failure mode for the ACR. As far as I can figure none of these modes of failure would cause your alternator light issue. But, that hypothesis should be easy to test:
1) disconnect the ACR/house circuit. You can do this by disconnecting the ground side of the house battery or even disconnect the wire going to the ACR from the starter battery at the starter battery post (but be sure to do this properly, disconnect starter battery ground first, then reconnect after the ACR circuit is removed)
2) see if your issue persists by starting up the van and seeing if the light comes on AND backing that up with a voltage reading using a multimeter both at the starter battery itself and at the positive post of the alternator.

If the issue is still there (light is on or no charging voltage seen), then the issue is definitively in the "stock" charging configuration and is probably an issue with the alternator itself (I would look at the voltage regulator).

Hope that is helpful.
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PostPosted: Wed Jul 10, 2019 11:53 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

SyncroButter wrote:
General question for the peanut gallery to confirm since I don't have my bentley in front of me: assuming a "stock" Vanagon wiring setup with only a starter battery (no house battery or ACR) the alternator light functionality is an indicator of only charging circuit voltage right? Like if I had a starter battery with dead cells that will never take a charge but have the van running with a good alternator, the charging circuit would have ~14.2V anyway and the alternator light would not be on correct?

No - the alternator tally lamp has 12V from the battery on one side. When the engine is started, current flows through the lamp towards the alternator along the blue wire. This is an 'exciter' current for the alternator, which will then start producing current itself. Now you have ~14V on the output to the battery AND on the alternator end of the blue wire. The tally lamp has battery on one side and working alternator voltage via the blue wire on the other, so remains unlit, as there's no (or very little) voltage across it.

If the battery has a shorted cell or two there might not be enough current to get the alternator going so the lamp remains on and the battery never gets charged.
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PostPosted: Wed Jul 10, 2019 12:24 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Yes, you are generally correct. The dash led charging indicator tells us nothing about whether any amperage or charging voltage is actually reaching the battery, only that the alternator itself is turning and generating something. But because various models have can unrelated items wired to the blue wire circuit the exact behavior of the dash led is open to normal variations that may make a side by side comparison of the behavior appear slightly different in 2 different vans of even the same year.

Also you are right that the ACR should not be playing any role in the OP problem since it shouldn't be turning on until it sees a charging voltage which supposedly isn't present during this problem.


In my opinion people who are relying on their aux battery in a serious way should have permanently wired in voltmeters for both the starter battery and aux battery circuits so they can see what is going on at a glance.

Mark


SyncroButter wrote:
General question for the peanut gallery to confirm since I don't have my bentley in front of me: assuming a "stock" Vanagon wiring setup with only a starter battery (no house battery or ACR) the alternator light functionality is an indicator of only charging circuit voltage right? Like if I had a starter battery with dead cells that will never take a charge but have the van running with a good alternator, the charging circuit would have ~14.2V anyway and the alternator light would not be on correct? .......
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PostPosted: Wed Jul 10, 2019 12:43 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

fxr wrote:

No - the alternator tally lamp has 12V from the battery on one side. When the engine is started, current flows through the lamp towards the alternator along the blue wire. This is an 'exciter' current for the alternator, which will then start producing current itself. Now you have ~14V on the output to the battery AND on the alternator end of the blue wire. The tally lamp has battery on one side and working alternator voltage via the blue wire on the other, so remains unlit, as there's no (or very little) voltage across it.

If the battery has a shorted cell or two there might not be enough current to get the alternator going so the lamp remains on and the battery never gets charged.


Ah, thanks for the clarification... so the lamp is both path for the initial exciter voltage path as well as indicator of any delta in V between V at the exciter and V at the battery post. Cool!

Coming at this from another angle: Assuming a state where the engine is running and alternator is pumping out the correct voltage/amps (meaning the exciter already did its thing) there would be little chance for the light to illuminate right? i.e. if I understand your explanation correctly you would need some sort of strange situation where the voltage seen at the voltage regulator/exciter has delta with the voltage seen at the charging circuit at the battery... assuming the volts and amps are correct at the alternator that situation seems possible but pretty unlikely.

Poor choice on my part to use the bad cell analogy... what I was really trying to get at is that the alternator/voltage regulator is where I would concentrate my attention since the battery itself could be in fairly poor shape and still not trigger this set of symptoms, but I missed the possible failure mode with the exciter voltage where root cause is in the battery itself so thanks for calling that out. OP states that V at the battery when light is on/not charging is "below 12.7 volts" but assuming that is not code for "8 volts" or something (and knowing that the starter battery is healthy enough to start the van... unless the ACR also has the wiring added where it connects both batteries during start, which is an option with the Blue Seas ACR) then it would seem unlikely that the battery is so toasted that it cannot get the exciter field up and running, and we can probably assume from the lamp functioning that the exciter circuit itself is OK. So, my money is still on voltage regulator.
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PostPosted: Wed Jul 10, 2019 12:53 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

In VW instrument clusters of our van's time period the dash led itself is not a critical path for the alternator exciter current. VW installed a bypass resistor in parallel to the led and the majority of the exciter current goes around the led passing through that resistor path. So even if the led was burned out or missing there would still be most of the exciter current flowing. In later years VW increased the current through the bypass resistor to I assume help the alternator begin charging without the driver needing to tap the throttle.

The dash led is critical for warning the driver that something is wrong, so he STOPS RIGHT NOW and looks at things. The same belt drives both the alternator and the water pump so it is extremely important to inspect IMMEDIATELY if the alternator warning light comes on while driving or stays on after starting the engine.

Mark
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PostPosted: Wed Jul 10, 2019 1:11 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Thanks all for the great replies, they all provide much needed insight. I'm still waiting for my van and will be doing some testing as soon as it's back.

In the meantime, a few precisions:

- Starting battery is new and is always above 12.3 V.
- Alternator is a few years old, and I would expect it to still be in top shape.
- I have a voltmeter set up for the aux battery, and will be putting one in for the main battery as I now see this as extremely valuable.

I also do not believe the SI-ACR is part of the problem, as everything has been fine for several months. The relay functions perfectly and, when the alternator does kick in, both batteries are getting charge.

Since I have recently needed to rev the engine up to 4000RPM to get the light to go off, it is my understanding that the exciter circuit is absolutely at fault -- at 4000RPM, from what I understand, the alternator will self-excite on its own, although not always (and this is pretty much what I have been getting).

The ONLY thing changed recently, i.e. right before this problem started, is that I took the 12V wire feeding the Dometic fridge out of the original fuse box behind the driver's seat and plugged it in directly to my aux fuse panel -- my aim was to no longer need to start up the LP mode each and every time I stop to eat while on the road. Because the relay that feeds this wire is triggered by the blue alt wire, I am wondering if this could have something to do with the whole thing. I'll be testing this by putting the fridge wire back in its original place and starting up the van...

Otherwise, can anyone point me toward the best way of finding out if/where my blue wire is going to ground?
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PostPosted: Wed Jul 10, 2019 1:17 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

crazyvwvanman wrote:
In VW instrument clusters of our van's time period the dash led itself is not a critical path for the alternator exciter current. VW installed a bypass resistor in parallel to the led and the majority of the exciter current goes around the led passing through that resistor path. So even if the led was burned out or missing there would still be most of the exciter current flowing. In later years VW increased the current through the bypass resistor to I assume help the alternator begin charging without the driver needing to tap the throttle.

GW even have a add-on kit (which is just a resistor) to eliminate the 'LED stays on until revved' situation.
Quote:

The dash led is critical for warning the driver that something is wrong, so he STOPS RIGHT NOW and looks at things. The same belt drives both the alternator and the water pump so it is extremely important to inspect IMMEDIATELY if the alternator warning light comes on while driving or stays on after starting the engine.

Mark

^^^^ This!
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PostPosted: Wed Jul 10, 2019 1:22 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

By far the most common cause of the light staying on is the blue wire loosing it's connection at the alternator. I would always start there.

Even when you turn off the engine the alternator retains some residual magnetism for a period of time. But if you leave it parked long enough this magnetism will slowly fade and may be completely gone. At that point you need the blue wire to get things going again. If you drive it every day it could start charging each day even if the blue wire has fallen off or broken inside the insulation, using just the residual magnetism and higher rpms to get things started. Since the engine moves around while running these things happen, mostly right at the alternator or within a few inches up the blue wire.


There is a connection point along the blue wire path inside the engine compartment wiring box. That is another place where the blue wire sometimes looses connection to the alternator. It is also a place where you can test the blue wire.

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PostPosted: Wed Jul 10, 2019 7:18 pm    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

OK, update and a question:

When my mechanic pulled the blue wire from the D terminal on the alternator, the indicator light stayed on, indicating that the wire was grounding somewhere along its path.

When I got the van back, I started my explorations with the relay beneath the driver's seat (the one where the blue wire triggers a 12V supply to the fridge). The relay was no longer in use, as I hooked the fridge up directly to the aux battery recently (for sporadic use when stopping during a drive). When trying to pry the blue wire from the relay, the whole thing kinda fell appart. With the blue wire unhooked from that relay, there was no longer any grounding. When I got back to the alternator and disconnected the blue wire, the charge indicator light in the instrument cluster no longer lit, either with KOEO or with KOER.

My alternator is no longer producing any charge, even at 3000-4000 RPM, and even when tripping the D terminal. So I'll be changing this somewhat recent alternator in a few days.

My question: could the obviously faulty fridge relay have contributed to my alternator dying so soon? I now recall the the 16A fuse behind the driver's seat kept blowing, and I never could figure out why.

Or, could the 110AH aux battery through the SI-ACR be too much for my alternator? (I doubt this, as I have seen many using a similar setup)...

Any help would be greatly appreciated, as I hope this won't be a recurrent thing.
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PostPosted: Thu Jul 11, 2019 7:09 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

And another question:

I pulled the blue wire from the D terminal on the alternator in order to measure its voltage once engine is running. It measures in at roughly 11.5 V. Is this normal, or is there a voltage drop somewhere? Will 11.5V be enough to excite the new alternator once it is installed?
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PostPosted: Thu Jul 11, 2019 8:12 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Why don't you pull the brush/regulator assembly out? It takes 1 minute and is a cheap and easy part to replace compared to changing the alternator. If the brushes are worn and not contacting it won't charge.
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PostPosted: Thu Jul 11, 2019 8:34 am    Post subject: Re: SI-ACR Aux battery setup - alternator light issues Reply with quote

Yes, try changing that part alone and see if it does it. You can get a new regulator/brush assembly for less than $20 and I consider it an essential spare part to carry, along with an ignition switch, and alternator belt etc.

I buy new ones that have a higher voltage set point of 14.5v or so.

Mark



Steve Arndt wrote:
Why don't you pull the brush/regulator assembly out? It takes 1 minute and is a cheap and easy part to replace compared to changing the alternator. If the brushes are worn and not contacting it won't charge.
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