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Guest Message by DevFuse

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Voltage Regulator

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13 replies to this topic

#1 Guest_subaru1800_*

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Posted 18 October 1999 - 12:25 PM

I recently swapped in another alternator into my '86 Wagon. The old alternator never charged above 10 volts, the 'new' alternator fluctuates between 12 and 17 volts, depending on RPM. Before I buy a new voltage regulator, is there anything else that could be causing the trouble?

#2 Guest_ShawnW_*

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Posted 18 October 1999 - 04:28 PM

Well I think a poorly grounded connection, usually the ones near the battery where it screws into the body are rusted.

#3 Guest_Skip_*

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Posted 19 October 1999 - 02:53 AM

Thought the VR was internal in 86? Are you sure this new-2-you alt is for your year car? My 87's voltage varries for 12 to 15 depending on load and rpm. 17 would be alittle high.

#4 Guest_subaru1800_*

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Posted 19 October 1999 - 05:14 PM

Thanks Shawn & Skip. I rebuilt the VR and it fixed the problem. (Yes it is internal for ALL Subarus, but it is to easy solder-in new diodes. If anyone needs help doing this, let me know.) P.S. Skip, Your voltage should never fluctuate more than .5 volts at any RPM with a good electrical system. A good subaru alternator and strong battery should be able to maintain voltage at idle even with headlights/stereo/everything on. The voltmeter in the instrument cluster, however, will fluctuate drastically with the heater fan or other things that run off the same source lead. Use another voltmeter for good measurements. The rectifier circuit in the alternator is tuned to 14 volts. You should read approx. 14 volts at the battery at any RPM above idle.

#5 Guest_doctor_*

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Posted 20 October 1999 - 10:46 AM

I'm having a problem with my alternator on my 84 GL. I was wondering where you got the replacement parts to rebuilt the voltage regulator?The alternator charges ok and the voltmeter works, but the light is staying on. I isolated the problem to the alternator (by using the one from my Hatchback), the voltage going out to the lamp is too low. I also have a spare alternator that is completely dead and would like to repair that also. Thanks in advance

#6 Guest_Mike W_*

Guest_Mike W_*
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Posted 20 October 1999 - 05:14 PM

I think a new diode might be in my future as well. It's good to hear that the VR is rebuildable. I remember reading about so many guys getting new alternators due to a bad VR, I assumed it wasn't possible so fix it. If you could post a quick run down on how you did the VR rebuild it would be much appreciated. Thanks!

#7 Guest_Skip_*

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Posted 21 October 1999 - 02:57 AM

The voltmeter I am monitoring is connected to the cig liter and has a digital output. I am experiencing the fluctuations and at idle all the dash warning lites glow very dimly even though I'm showing 13.8 v on the meter. My headlites are 100 w highbeam w/ a pair of 100 w driving lites relayed to come on with the hibeams, I still maintain 14 v with them on. If I turn the heater blower on high, even without the beams on I can only get 12.5v regaurdless of the rpm. Any hints on where I'm dropping the voltage?

#8 Guest_subaru1800_*

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Posted 21 October 1999 - 05:44 PM

Skip, I think its likely that the heater blower and voltmeter use the same source lead, which might be a little insufficient (from day 1) for everything a Subaru has under the dash. As far as the Alt. rebuild-- -remove the pulley (you can use an allen and a socket/visegrip combo). -remove the four long screws from the casing. -separate the halves. The stator (middle of the casing) stays with the back half. The rotor and bearings stay with the front. -remove the nuts from the back half of the casing and unsolder the two stator leads. -remove the circuitry. You will likely have either a silver (solid state?) or a black package soldered to the frame. If you have the silver package, you likely have to replace the entire unit ($9 at a local Schucks). If you have the black package, you may not have to unsolder the entire thing. I cut open the casing and found a bad diode on the top layer. I matched the colors at Radio Shack and $.79 later had a good alternator. I would have replaced the VR but I couldn't find my part anywhere. I found plenty of the silver ones, though. -replace the circuitry and re-solder the stator. -now would be a good time for new bushings, but none were available to me in the local area. -reassemble the casing by alternatly tightening the screws. Do not overtighten them, as it will impair the movement of the rotor. Please let me know if I left anything out or can be of any help. -Nick

#9 Guest_subaru1800_*

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Posted 21 October 1999 - 07:27 PM

It might make reassembly a little easier if you do this: Before you join the two casings, push the brushes into their slots and hold them there with a pin (like a paper clip) inserted through the hole in the back of the casing. -Nick

#10 Guest_Mike W_*

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Posted 21 October 1999 - 10:41 PM

Thanks for posting that Nick. I cleaned the posts on my battery yesterday and haven't noticed the voltage jumping around since. However the irregular voltage was kinda sporatic when it happened in the past, so I may still get to look at the inside of my alternator. Say uh, suppose maybe your method could be added to the collective wisdom in the "knowledge base" section of Geoffrey's web site or archive it here on the board? It'd be great to be able to refer back to your description when rebuild time comes and it might save others from replacing the whole alt. Thanks again!

#11 Guest_ShawnW_*

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Posted 22 October 1999 - 12:29 AM

Well the archival thing is a definate good idea. When you guys are done discussing this Ill move it over 4 ya, or another moderator/BillyC could too.

#12 Guest_Skip_*

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Posted 22 October 1999 - 02:12 AM

Would not be a bad time to look at the brushes, they usually have a wear indicator mark in the longest flat side, they are also cheap and can cause an alt to go south in strange ways. Can cause a coming and going of the output. Nick, I agree that the main source feed from the fusible link might be the culprit in my case. Do you happen to know where and what color this wire is? I'd like to run another say 12g in parallel. May test the theory by running a wire to the bat and monitor the voltage there. I also believe the fusible links' spade connectors can build up corrosion and act like resistors thus dropping voltage across them.

#13 Guest_subaru1800_*

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Posted 25 October 1999 - 11:57 AM

Skip, you're right about the brushes. I would have replaced them but I couldn't find them locally. I've been lucky enough to never have to locate the main wire to the fusebox. I don't think car makers find anything wrong with using a small feed wire as I've noticed even new cars not having enough juice with everything on. My wife's 98 Suzuki Esteem does it, too. (At least Subaru never gave a car a stupid name like Esteem. I can never drive drive it in the mountains, 'cuz my esteem would be going downhill. I can't park it on the side of the road, either, 'cuz my esteem would be in the gutter.) -Nick

#14 exister99


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Posted 02 September 2003 - 09:33 AM

Time to resuscitate this thread!

I just ordered a couple of sets of brushes from partsamerica.com for $6.59 a pair.

Does anyone know if every alternator in '80s Subarus uses the same size brushes?

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