Electrical gremlins.... voltage related

[Caboobaroo]

So I've been having this problem where I'll only be putting out like 11.5 volts at idle when the car finally warms up. So a couple days ago, I have a car full of people coming back from Seattle (downtown in about 30 minutes from my place) and I notice my wipers are going real slow. Look down to my voltage gauge and its way below 12 volts, then look at my stereo since it has a built in voltage gauge and its only ready 11 volts at 3500 rpms. It slowly dies in about 15 miles to just over 9 volts where I can feel the car start sputtering at higher rpms so I know its time to get off the freeway and park it in a parking lot. Tried to start t couple times after shut off and its still at 9 volts, then it won't start up again. STart calling around to see if my buddy can come pick all 4 of us up, then after I getoff the phone (about 10 minutes later), I jump in the car and start it up again. 13 volts at idle. I drive home and it never goes below like 12.6 at idle. Park the car for the day because I'm pissed.

 

So this happened 2 days ago. Yesterday I go out to go to work and I start it up. 11.8 volts at idle when its cold. Decided that since I only live like 5 minutes from work, I'll make it. Had only dropped down to 11.5 volts by the time I got there. So at the end of the day, I go out, start her up, same thing, 11.7 volts or so at idle when cold. I get on my way home, have a little traffic to deal with but coming up to my place, I look down at the stereo and the voltage is slowly dropping off. Get to my place with it sputtering, make it up the hill and park it. So now I'm pissed, no Christmas lights on the dash and me going:confused: :confused: . I'm thinking it might be a battery issue since the battery is about 5 years old and its gotten a hell of a beating from being in my lowered RX.

[Quidam]

I was driving up the interstate, 1989 spfi, sedan. The voltage starts dropping. I keep driving for several miles. I'm running late and I'm going to see a relative pull with his Hemi Dodge truck.

 

I just make it to a Wallmart. Buy a new battery. Drive to the track. At two in the morning after it's over, I change the alternater in the parking lot. Had it in the trunk. The alt was bad. It had acted up before.

 

Just a story:)

[DaveT]

The gradually dropping voltage sounds like the alternator isn't putting out power. At even 1000RPM you should be over 12V. All of my alternators (like 3 cars) wore out 1 of the brushes around 140K miles, no lights on the dash to show no charging, just eventually no start, slow crank or happened to notice the low volt meter.

 

Your battery is near end of life anyway, at 5 years. Maybe use it through the summer, get a new one before cold weather.

[ScottG]

Same thing happened to me twice on my '86 GL Wagon.....the voltage indicator just starts to drop....until you suddenly notice the gauge. And BTW, my Soob has a CHARGE light on the far left of the dash. It comes on when the key is in the RUN position, just before START. After the engine starts, the light goes out.........but the 2 times the alternater failed, THE BLASTED LIGHT NEVER CAME ON!!! What's with that????? Anyone else ever have that happen on an SPFI EA82??

 

A bright red light catches your eye a whole lot faster than a slowly sinking volt gauge.

[tizzle]

Don't you have a fancy battery/alternator tester at work?

[Durania]

Sounds like your standard bad/worn out alternator.

[Alaska Style]

My 89' SPFI Wagon started fluctuating from 10~18 volts and I had to constantly monitor and switch on/off high beams, rear defrost and heater fan to maintain 12ish volts. Also, my Brake light, Charge light, and E-brake light has been on sence this started a month ago. It's had good days where it's fine and some days where it'll max out the volt guage even with all loads on high. I removed and inspected and cleaned and reinstalled the cables/wires and still no change. 3 Red dash lights on full time, even on a nice 12V day. I put in a new 140 AMP alternator and the dash lights never came on again. I still don't know why the brake light came on. They also glowed and flickered, the new alternator fix it. Weird.....

[GeneralDisorder]

Alternators fail in a multitude of ways. Each one has it's own set of symtoms. Once you understand how an alternator works, it's relatively easy to work out what failed. Here's a quick run down off the top of my head:

 

1. Bearing failure. This usually just causes noise, but the vibration can cause the brushes to arc and this will damage the regulator and rectifier.

 

2. Rectifier diode failure. This happens when one or more of the diodes in the rectifier bridge fails. This WILL result in some measure of Alternating Current to pass through to the system. AC doesn't charge batteries, and it doesn't allow the regulator circuits to work properly. This has the side effect of defeating the diode's in the warning light power circuits of the guage cluster and causes them to glow dimly or "flicker" as the half-wave rectified AC current flows backwards through the shared power circuits of many of the warning lamp bulbs. This is what people refer to as the "Christmas Tree" and is one of the more interesting, and poorly understood of the alternator failure modes.

 

3. Regulator Integrated Circuit failure. This happens usually because of heat (bearings, ect), or because some other component failed and put too much strain on the regulator circuits (usually resulting in a heat failure). This causes the alternator output to go above or below the "regulated" output (14.5v +-0.3v) - depending on what exactly failed in the circuit. This is where you see either the whole system run out of power, or the voltage spike up to 15+ volts. If the regulator fails low, then to a lesser or greater extent the "charge indicator" lamp will glow. What people fail to understand is that the charge indicator is not an all-or-nothing type of lamp. It indicates the differential between the battery output and the alternator output. If the battery is putting out 12.5, and the alternator is putting out 11.5, then you have only a 1 volt potential across the charge indicator - it will glow VERY dimly - probably so dim you can't see it in daylight. Thus the alternator is not charging the battery - as the input voltage to the regulator dies off, so does the output, and you have a situation where the battery dies, the car dies, and you are left wondering why the charge indicator didn't come on. You just have to understand what is going on, and what that lamp is reading. It illuminates when you turn the key to "on" without the engine running because there is 12.5 volts potential across it due to the alternator not spinning at all.

 

You also need to understand that any one of these failures can QUICKLY lead to any of the others - as in within seconds under the right conditions. So what you usually have is a combination of these failures.

 

GD

[Caboobaroo]

Well I kinda hoped it wasn't my alternator since I had replaced it before since it kinda went out as well (Christmas time on the dash) but I'm going to replace it with a new unit instead of a used one.

Also going to replace the battery as well with the Optima yellow top. Gotta love discounts from work.

 

Oh and Tizzle, the machine doesn't work when you can't get the car to it:-\

[robm]

I suspect either a sticky brush or a flaky regulator. Are the brushes available as separate items? Maybe jsut get a new one, more $ but better longevity.

[naru]

4.Worn brushes-subaru 495747601 about $6

Checkem before spending big $`s.

 

Eliminate the battery from the diagnostic equation by dissconnecting it.

[Caboobaroo]

Well I need to do an alternator upgrade for now since I'll eventually be going EJ with the car.

 

I could rebuild the alternator but I'll end up killing it again since I do have a pretty decent stereo in the car. I've heard about using a Nissan Maxima alternator from an '86 on it so tomorrow I'm going to get one from Napa and give it a shot.

Then an Optima Yellow Top:banana:

[The Beast I Drive]

Why the yellow top? I like the red tops myself... If I recall, the Blue ones are deep cycle for marine use, but what was special about the yellow ones? I forgot :-\

[Caboobaroo]

Yellow tops are made to handle the bigger power drains in cars with audio systems (like mine), offroad lights/winches and such or the combination of both (my Toyota). The red top is good for "better then a stock" battery but Optima doesn't like to warranty them out when they've been used in cars with massive power drains. Even though I work at Les Schwab and get a discount on them, they get a little more picky on the warranty of them:-\

[The Beast I Drive]

oohhhhh I see, I guess I should start running one of those in the Beast, my amp and my 100 watt offroad lights do draw a lot of power, especially running together. I want to do an alternator swap as well, but Im kinda lazy, and Ive only had to swap 1 alternator...

[Cougar]

Be sure to check your fusible links also. There may be a bad connection to one of them.

[Alaska Style]

oohhhhh I see, I guess I should start running one of those in the Beast, my amp and my 100 watt offroad lights do draw a lot of power, especially running together. I want to do an alternator swap as well, but Im kinda lazy, and Ive only had to swap 1 alternator...

 

I highly recommend one of theese ones, Their EXTREMELY tuff, and pretty darn easy to drop in an EA82. cheep 14O or 16Oamps, Large case, big bearing never worry last forever kinda thing. 85 bucks!!!! LEECE NEVILLE has ALOT of output options gettin in the hundreds of amps and are easily rebuildable/up-gradeable. http://cgi.ebay.com/ebaymotors/PRESTOLITE-140-AMP-LEECE-NEVILLE-110555-ALTERNATOR_W0QQitemZ180217291992QQcmdZViewItem?_trksid=p3286.m20.l1116 http://www.prestolite.com/literature/alts/PP1131_110-555.pdf

 

"ps. I have 2 belts now"

[Caboobaroo]

Well I replaced the alternator with a new one from Napa and go figure, it works:rolleyes:

 

Glad I got a lifetime warranty though so if it should fail between now and EJ time, free replacement:banana:

[Quidam]

"ps. I have 2 belts now"

 

I'm still in awe of the things I learn from board members here. I've got one of these on the shelf, but never considered throwing it on a Subaru:) It needs rebuilt.

 

Doug:Edit: Mine is 130 Amp. I have an older GM that was hopped up, fancy tag, and $180.00. I've had it for years and it was a large purchase, at the time. Hasn't been on a Subaru yet, tho. 90 Amp @ 200* F.

[Gloyale]

Eliminate the battery from the diagnostic equation by dissconnecting it.

 

Great idea if you don't like you're ECU.

[audio_file]

hi everybody!!

 

i'm resurrecting this because i know i've got and issue, i just don't know which it is after doing some searching . . .

 

on my 87 gl EA82 3AT carb'ed wagon w/118k . . .

 

my voltmeter in the car started bouncing a few days ago, and the lights (interior and exterior) started to "strobe" with the voltmeter. (a lot like the x-mas tree stories above ^^ but without the red lights) its like my car is having a party and i'm not invited any time you are not accelerating or raising rpms, the voltage meter starts to bounce not just move, bounce- like a monte carlo on 100 spokes . i plugged my multimeter into the elec. system and had these results:

 

in the morning, before turning car on, my optima red top showed just under 13v at the battery.

 

turn the car on without running any accessories and the battery starts to gain voltage, up to about 14.7 and then fluctuates like the voltage meter on the dash, rapidly going between 14.2 and 14.8 and never more or less than that.

 

turn on accessories with the car running, and the voltage kinda evens out, the same way it does when the car is accelerating . . . staying around 13v, how do i know, because the dash's voltmeter stays right in one spot, doesn't move.

 

measured the voltage from output on alternator vs. ground on batt and on car and the multimeter says 14.4 14.5 almost always. but if you measure it at the battery, there's much more fluctuation

 

my multimeter only goes up to 10amps, so i don't know how to read the amperage outputs at the alternator. the really frustrating part is that i'd just installed a new alpine cd player, and somehow- this has fried that. didn't blow the little fuse on the unit or the big one in the power line, just killed the cd player (i ran a dedicated, fused power in and dedicated ground and still get nada = toast, right?) one more thing, if you unplug the 12gauge power wire that i ran to the stereo and put a multimeter on it at the battery's end while it's still plugged in on the stereo end, the multimeter reads 2.4 to 2.6 volts, coming from the stereo that otherwise just sits there, dead!! (?)

i've been over the stereo wiring over and over again (ran dedicated speaker wires too, clear to each speaker) looked at the grounds in the engine bay, measured voltage (or lack thereof) just about everyplace i can think of.

 

so . . . is there any more info you need? is this alt related, voltage reg related or other?!!!

 

after 2 days of trying to track this down, it's really starting to fry my dome, and it seems like each person's elec problem threads are unique, i haven't found one that sounds closer to my problem than this one . . .

 

HELP

chris

[DaveT]

This sounds tricky, here are few things that come to mind:

 

I'm thinking most likley is the alternator or regulator.

 

Check for bad ground - connect one meter lead to the case of the alt. the other to the battery -. You should only see a small voltage. Try different load / no load / engine on / off.

 

The mystery voltage on the stereo power lead could be leakage from a control line - on / off or clock? Or if it has a large capacitor on the input, it would hold a couple volts for quite a while with only a meter connected.

 

I'm guessing the battery is ok - It cranks the engine, has normal (slightly high) resting voltage. A good flooded cell battery ranges from 12.0V (full discharge) top 12.6V (full charge) AFTER sitting for a number of hours with no loads. The Optima is a starved electrolyte cell, so the exact numbers might be a little different.

 

To measure high current you need a shunt.

Cheap way: get a length of wire - like 12" of #10 or #8. Look up the ohms per 1000 feet. Do a little math to figure out how many ohms you have. Connect the wire in series with the circuit to measure, connect your VOLT meter across the measured lenght of the wire. Ohm's law to get the current. As long as the shunt wire does not get warm, the reading will be accurate enough.

 

Middle cost way. Find a surplus .001 ohm 1KW resistor. It works very nice for this. I got the one I have a very long time ago, so I have no idea where to get another, unfortunately. Google/ebay??

 

Expensive way: $2000.00 Tektronix current probe. clips right onto the existing wire.

 

 

Disable / remove fuses from all circuits not needed to run the engine, see if anything is causeing weird loading?

 

Swap the alt / battery from another car?

[Ziggy]

It sounds like excessive voltage drop from the alt output wire to the batt.Volt drop should no more than .5 of a volt. Do you know how to check for a voltage drop? If not let me know.

[audio_file]

no, please explain . . .

[edrach]

I go with a faulty alternator. Drop me a call if you'll consider a used XT alternator. I have one in my "stash." Pay me after you've tried it for a week or so.