Losing Voltage

My '90 Acura Legend is losing power while the car is running. My volt meter reads 14 at the beginning, and about 2 minutes later, it reads under 13. I tested my alternator and it passed at auto zone. Any
suggestions?
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Are you turning on A/C or other accessories? MZ
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You don't mention the mileage, but guessing it's around 150K miles or so the alternator brushes are probably worn out. Often they are worse when warm, but mostly that is a marginal difference. Brush trouble shows up in the early stages as intermittent charging, and a '90 might be early enough that the warning light won't tell you anything is wrong. More recent Hondas use a separate sensing circuit.
If you are seeing the voltage pop up and down, gradually becoming more down than up, you are probably seeing the brushes make their last stand. Replacing the brushes, assuming you can obtain them, is a cost-effective approach. See Elle's web page on that at http://home.earthlink.net/~honda.lioness/id13.html - her site is tailored more for Civics but the principles are the same.
Avoid aftermarket rebuilt alternators. They have earned a reputation for poor reliability.
Mike
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It's bad. Replace the alternator. Voltage at idle should be 14.4V.
If you choose an aftermarket reman, it WILL fail in just over a year. Guaranteed. It does not matter where you buy it, NAPA, AutoZone, Kragen, they're all lousy.
If you spend twice the money to get a genuine Honda reman, you can install it and forget about it.
There is a slight chance the brushes are worn, but this normally manifests itself as a flickering charge light.
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RandyCamp wrote:

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Any time the alternator circuit is discussed, it's probably a good idea to SEARCH google and understand the Honda ELD, since it affects any measurements and might fool the AutoZone people, or yourself.
'Curly'
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I confess I don't understand the ELD. Do you have a good link for it?
Mike
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I'm not sure I understand it either. Found this link: http://www.asaaz.org/canyonauto/techtips.htm
See item six, "Honda Information".
The factory service manual is devoid of info on the ELD, strangely enough.
I'm also not sure the Legend uses an ELD. Too old, no? I have a Helm manual for the '91 Legend. No ELD is shown.
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