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Low voltage

I had an issue pop up the other day where my voltage gauge started to read low and would bounce down whenever I'd hit the brakes or less so with the turn signals. I was reading through some threads that said it could be only the Voltage Regulator, so I swapped them between my cars since I know there aren't any issues in the 84.

Afterwards I was still getting a low reading, but put my battery on a charger overnight so I can still get around in the meantime. This morning the gauge was reading around 13, but did go back down to the 12ish area after I got to work. I realize now that it may have been the correct voltage from being charged, but I wanted to get some other opinions first.

Should I be preparing to take the alternator off again to replace?

P.S. The alternator is a huge pain in the butt on the Turbos which I figured out yesterday.

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Old 04-18-2016, 02:57 PM
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Recommend you check your battery first:

Battery Checks

If the battery is good then you need to check your alternator. The voltage regulator is part of the alternator. Also check your battery cables.

You could also have a slow drain that is discharging your battery overnight.

Have Fun!
Old 04-18-2016, 03:57 PM
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+1 on checking the cables. Likely too much voltage drop to fully charge the battery.
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Old 04-18-2016, 04:38 PM
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Right:

1. Check battery
2. Check cables
3. Check for slow drain
4. Check alternator belt for slipping
5. Then check alternator...
Old 04-18-2016, 04:42 PM
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Sorry, I should have mentioned that I got a new battery this week. The other might not have been bad but I had killed it before so I wasn't sure if that was what left me stranded the other day.

The cable ends on the terminals look good, and the alternator belt was tightened after putting it back in. While the car is idling the battery is being drained slowly, but doesn't appear to be charging at all.

What is the best way to check the alternator itself?
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Old 04-18-2016, 05:27 PM
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When the car is running, put a voltmeter on the battery terminals. If it's not reading 12.5 or more, it's not charging. Especially if you're getting a reading of less than 12 volts..

If you put a new regulator in it and it's still not charging, it very well could be the alternator. Those Bosch units are pretty robust and don't fail that often. However, that doesn't mean it can't happen..
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Whenever I checked the battery while the car was on, it started at 12.7 and was slowly going down. I didn't keep the voltmeter on long but it went down to 12.69 almost right away and to 12.68 before I took it off to check the gauge on the dash.

I guess I'll look for another alternator. Is Bosch reman the way to go or are other brands ok?
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Old 04-18-2016, 07:01 PM
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regulator... Buy an universal remote adjustable one.
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Old 04-18-2016, 11:34 PM
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I'd take it off and have it tested first. I'd go with a used Bosch unit from a seller here. The only issues I've ever had out of them is the voltage regulator brushes getting worn down. Oh, and one time a gravel got in somehow and wedged against one of the brushes keeping it from making contact. It fell out as I was removing the regulator. I put the same regulator back in and it lasted another 10 years.. I'd do all I could to rule out the alternator before getting another one, they really are almost bulletproof.
Old 04-19-2016, 04:42 AM
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I guess I'll check everything again. I did take a working regulator and put on to the alternator in question but still wasn't getting any power. With my luck it will be the cables on the starter itself not completing the circuit.
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Old 04-19-2016, 01:45 PM
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Before you do that what is your volt gauge reading when engine is off, when engine is idling, when engine is idling with all accessories turned on, and at 2000 RPM?
Old 04-19-2016, 02:12 PM
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Engine off - around the 10v/lowest point

Engine on - A little above 12

Engine on w/ accessories - right about 12, unless I hit the brake pedal then it dips

All on at 2000 RPM - hovers just below 12


I'm going to head out now and check the cables again and test with the voltmeter.


Edit: Somewhat frustratingly, the voltage looks good today. With the car off the voltmeter was reading 12.7 and with the car running and all the lights on it was steadily at 13.4.

Anyone know off the top of their head if one of the ribbons on the gauge cluster is specifically for the voltage gauge? I'll check that eventually but I can live with it for now if the battery is actually charging.
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Last edited by MPitt; 04-20-2016 at 02:36 PM..
Old 04-20-2016, 02:11 PM
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If your engine off reading is only 10 volts, check it with a separate volt meter on the battery. Your gauge could be off a couple of volts. If it is really only 10 volts you could have a phantom battery drain (eg stuck relay or alarm or stereo drain)

But I would say your alternator and voltage regulator are fine. If your voltage regulator was bad you would see a major dip at step 3, down to 10 or 11 volts or lower.

If it is really 10V with engine off, check for a phantom battery drain. Clark's has a procedure...

Last edited by djnolan; 04-20-2016 at 03:13 PM..
Old 04-20-2016, 02:49 PM
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When I have an extra set of hands I'll check the voltage again with someone turning everything on, but I feel like at this point it could have either been the old voltage regulator that left me stranded or the old battery being bad, and that the voltage meter on the dash being inconsistent.

Thanks for all the advice though everyone.

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Old 04-20-2016, 04:00 PM
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