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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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 Posted: Fri Oct 03, 2014 7:58 pm Post subject: fluctuating voltage while driving |
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So i started the van up after sitting for a while, and it was a bit tough to crank. Then i drove around for 10-15 mins, and for some reason i was flipping through the scangauge (connected to subaru 2.5) and saw the voltage behaving strangely. What should it read? I was gettting sporadic readings between 11 and 16V. this seems high? There wasnt really any draw on the alternator, no headlights, fans, etc. All electrical systems worked fine when i switched them on and off.
Is it possible the alternator or voltage regulator is on the fritz? Or is there some variation in this voltage normally>? Does this reading come from the alt or from the battery? Is it possible that it is measuring battery voltage and this was going crazy as the alternator switched between charging primary and aux battery?
I havent driven the van since and am a bit worried about frying something if the voltage is wack? And advice is appreciated. |
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Dampcamper
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Joined: October 07, 2013
Posts: 788
Location: Rainy Portland, Oregon
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| Posted: Fri Oct 03, 2014 9:59 pm Post subject: |
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So do you have a Subaru conversion, then? Lots of electrical problems on stock VW have to do with bad grounds, I know nothing about Subaru grounding (or problems with grounds) but that would be a starting point - and one chronic problem place that you will still have is the braided ground strap between the nose of the transmission and the body. You can check that all you want, it might check good but be bad when you try to stuff a bunch of amps through it and it is shaking. Take it off, go down to any auto parts store and get a similar replacement. It isn't "just a VW part". Something close will work.
Also a known VW problem is alternator brushes wearing down, any chance that could be the case with yours? It doesn't hurt to run a heavy (#10 or larger) ground wire from the alternator to the engine block. Otherwise the ground return for the alternator is through the mounting bolts.
Clean and retighten your battery connections.
If you turn your headlights on does this change the voltage fluctuations?
Normal charge voltage will be in the 14.2-14.6 or so range. |
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Dampcamper
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Joined: October 07, 2013
Posts: 788
Location: Rainy Portland, Oregon
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| Posted: Sat Oct 04, 2014 12:33 am Post subject: One other thing to check: |
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While you're driving, have the headlights on, maybe the dome light in the cabin, too. Watch them to see if they are flickering at the same time as the gauge (voltage reads higher, lights get brighter). If the lamps flicker along with the meter jumping then the meter is a valid measurement instrument.
If the lamps do not flicker at the same time as the voltage changes, then the problem may well be in your instrumentation!
If this is a possibiliity, then I would suspect first the ground trees under the dash, left-hand side. It could be that the instrument's ground is bad, causing jumping readings.
Most aux battery systems nowadays use a form of combiner relay which ties both batteries to the alternator when it is making juice. They do not cycle between one battery and the other. There may be the exception out there... |
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vanagonjon
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Joined: July 17, 2006
Posts: 230
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| Posted: Sat Oct 04, 2014 4:08 am Post subject: |
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One easy check, get a male plug that goes into your lighter socket. I used one off of an old 12V accessory that was dead anyway. Then hook up your multimeter to it and plug it in and watch it at idle and while driving. You can then see if they agree, if so you have a voltage regulator issue, if not the wiring leading up to your scan gauge is faulty.
John |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Sat Oct 04, 2014 3:46 pm Post subject: Re: One other thing to check: |
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| Dampcamper wrote: |
While you're driving, have the headlights on, maybe the dome light in the cabin, too. Watch them to see if they are flickering at the same time as the gauge (voltage reads higher, lights get brighter). If the lamps flicker along with the meter jumping then the meter is a valid measurement instrument.
If the lamps do not flicker at the same time as the voltage changes, then the problem may well be in your instrumentation!
If this is a possibiliity, then I would suspect first the ground trees under the dash, left-hand side. It could be that the instrument's ground is bad, causing jumping readings.
Most aux battery systems nowadays use a form of combiner relay which ties both batteries to the alternator when it is making juice. They do not cycle between one battery and the other. There may be the exception out there... |
I will try with the lights on to see how the lights react. As for the instrumentation, the scangauge is an OBDII reader plugged into the OBDII port on the subaru engine, so no connection to the ground trees up front.
As for the battery combiner, this is what I have
https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A
I just checked and cleaned the ground from the transmission to the frame. Thought all was good but then the bolt spun in the frame. So maybe this is my problem>? I will buy a new ground strap (whats the recommended gauge?) and try and drill a new hole in the chassis if the existing one is stripped |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Sat Oct 04, 2014 3:49 pm Post subject: |
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| vanagonjon wrote: |
One easy check, get a male plug that goes into your lighter socket. I used one off of an old 12V accessory that was dead anyway. Then hook up your multimeter to it and plug it in and watch it at idle and while driving. You can then see if they agree, if so you have a voltage regulator issue, if not the wiring leading up to your scan gauge is faulty.
John |
Thanks, i will try that as well. As for the voltage regulator, this is a dumb question perhaps, but is this part of the alternator? Or a separate part? |
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vanagonjon
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Joined: July 17, 2006
Posts: 230
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| Posted: Sun Oct 05, 2014 5:37 am Post subject: |
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| It is a part of the alternator |
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jobenaus
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Joined: March 27, 2014
Posts: 100
Location: Yukon
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| Posted: Sun Oct 05, 2014 9:55 am Post subject: |
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| Mine does a similar thing. I've tracked it down to having a different rated and older battery as a house battery and the relay jumps back and forth trying to keep both batteries topped up. The marine battery quite a bit bigger and getting older so it seems to need more "attention" from the alternator. Don't know if this could be your issue? |
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Dampcamper
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Joined: October 07, 2013
Posts: 788
Location: Rainy Portland, Oregon
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| Posted: Sun Oct 05, 2014 4:22 pm Post subject: Re: One other thing to check: |
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| rfoubi wrote: |
As for the battery combiner, this is what I have
https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A
I just checked and cleaned the ground from the transmission to the frame. Thought all was good but then the bolt spun in the frame. So maybe this is my problem>? I will buy a new ground strap (whats the recommended gauge?) and try and drill a new hole in the chassis if the existing one is stripped |
That's the same relay I have. Make sure the relay has a good dedicated ground connection, not just tied into some brown wire somewhere. It senses voltage and connects the batteries together if within a valid charge range. A bad ground here could cause all kinds of havoc. As I recall that relay is set up to work on 12 or 24 volt systems, sensing the proper voltage for either...I wonder if it sensed 16.5 volts it would think, "Ah, too low for a 24 volt system" and then shut off the connection? This would make things jump.
I'd use a #4 or larger (#2?) jumper. [Edit: This would be the jumper on the front of the transaxle. For the Blue Seas ACR a piece of #16 or #18 will work fine!] My local Interstate Battery store has braided bonding cables for sale, not too much money. It doesn't have to be a specific cable, just flexible and lots of copper.
Also - there is no problem with installing a second, heavy-duty ground connection between, say, the engine and a good chassis ground point. This is not rocket science, go from a good engine bolt point to a chassis bolt, do the star-lockwasher, scraped paint and dielectric grease thing here, too. |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Mon Oct 06, 2014 3:40 pm Post subject: Re: One other thing to check: |
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| Dampcamper wrote: |
| rfoubi wrote: |
As for the battery combiner, this is what I have
https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A
I just checked and cleaned the ground from the transmission to the frame. Thought all was good but then the bolt spun in the frame. So maybe this is my problem>? I will buy a new ground strap (whats the recommended gauge?) and try and drill a new hole in the chassis if the existing one is stripped |
That's the same relay I have. Make sure the relay has a good dedicated ground connection, not just tied into some brown wire somewhere. It senses voltage and connects the batteries together if within a valid charge range. A bad ground here could cause all kinds of havoc. As I recall that relay is set up to work on 12 or 24 volt systems, sensing the proper voltage for either...I wonder if it sensed 16.5 volts it would think, "Ah, too low for a 24 volt system" and then shut off the connection? This would make things jump.
I'd use a #4 or larger (#2?) jumper. [Edit: This would be the jumper on the front of the transaxle. For the Blue Seas ACR a piece of #16 or #18 will work fine!] My local Interstate Battery store has braided bonding cables for sale, not too much money. It doesn't have to be a specific cable, just flexible and lots of copper.
Also - there is no problem with installing a second, heavy-duty ground connection between, say, the engine and a good chassis ground point. This is not rocket science, go from a good engine bolt point to a chassis bolt, do the star-lockwasher, scraped paint and dielectric grease thing here, too. |
Awesome, thanks. The more i read, the more I realize how important good grounds are, and how problems with grounding sometimes manifest in very strange ways. Will fix up tranny ground and probably add engine and starter grounds. Seems like a good idea. |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Fri Jan 09, 2015 3:14 pm Post subject: Update |
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Hey Guys
I havent been able to work on the van for months, but now that i have some time, here is what I have done:
New Ignition Switch
New Ground Strap from tranny to clean ground on chassis
New Ground Strap from starter battery to ground bolt under passenger seat
New 4Ga wire from alternator to starter. This should maybe help with my problems, and at the least help the alternator pump more juice to my dual battery setup.
In the process of redoing the alt-starter wiring, I have been a bit confused.
The subaru (mitsubishi electric actually) alternator, in addition to the main 4 (used to be 8Ga) wire to the starter post, has a plug with 3 wires in it. From my understanding, one plug is not used with this system. (the wire was taped up and did not connect to anything. )
The other two wires are the field current wire, and the voltage sensing wire. Correct?
Field current being the one that connects to the blue wire that eventually goes to the idiot light.
The other wire is presumably the voltage sensing wire. Which in my van, has been spliced into the main alt to starter wire.
From reading on this site
http://www.pirate4x4.com/tech/billavista/Wiring/Part2/
which has been super informative, by the way,
it seems like this current sensing wire could/should actually be run up the van to the main fuse block or distribution point. My question is, is this necessary, and if so, where exactly do i run it? I have a blue seas ACR and aux battery fuse block located adjacent to the starter battery, and then everything else is run off the stock VW fuse block/wiring.
Also, in relation to the fluctuating voltage, the coolant warning light comes on sporadically. Seems like when i mash the throttle, coolant warning goes on, and then when i throttle back, it goes off. Probably related to the voltage? Coolant is fine and sensor/wiring new.
Final question. I have heard people having good results grounding the starter and/or alternator with a wire, rather than just through the bolts. SHould i ground them together and run the wire to the tranny ground point, or do i just ground them with a short wire to the nearest ground/frame. And finally, since these are high current items, i assume i should ground with something like 8Ga or larger (I have lots of 4Ga left, is this overkill?)
SOrry for the extremely long winded post, and i will wire it all up and take it for a test drive on the weekend to keep you posted. Thanks again  |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Fri Jan 09, 2015 5:28 pm Post subject: |
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| latest: havent run around the block, and havent grounded alt or starter, but redid all wires, and connected current sense wire to alt terminal for now, and it fires up super good and strong. Think I am making progress. |
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rfoubi
Samba Member
Joined: March 21, 2004
Posts: 224
Location: Rossland BC
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| Posted: Mon Jan 12, 2015 12:43 pm Post subject: |
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I'm still wondering where to hook the alternator sense wire to. The main power to the fuse block at the starter battery post? Or at the fuse block itself? Or elseswhere?
I am now in the process of grounding the starter and alternator, and upgrading my alternator while I'm at it. Starter seems great now that the wiring has been upgraded, so i will just keep the new starter as a spare. |
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Syncro Jael
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Joined: December 19, 2013
Posts: 2204
Location: Utah
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| Posted: Mon Jan 12, 2015 5:11 pm Post subject: |
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| rfoubi wrote: |
I'm still wondering where to hook the alternator sense wire to. The main power to the fuse block at the starter battery post? Or at the fuse block itself? Or elseswhere?
I am now in the process of grounding the starter and alternator, and upgrading my alternator while I'm at it. Starter seems great now that the wiring has been upgraded, so i will just keep the new starter as a spare. |
From what I have read the alternator sense wire should go to the battery terminal. Use a heavier gauge wire so there will be less resistance. That is what you are trying to do is let the alternator be looking at the battery voltage and not the voltage from the resistance drop in the old wiring.
Here is a diagram I got off another thread that lets you understand.
Here is some information on the sense wire and its proper function. This is for Toyota, but the sense wire hookup is identical. Some of the other information doesn't apply, as the Toyota uses a third IG wire that the Subaru does not.
http://wilbo666.pbworks.com/w/page/39441708/Toyota%20Alternators#AlternatorRegulatorSTerminal
_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat) |
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