Electrics problem

[shiftless]

Before I head out to my friendly neighborhood shop and ask them to fix a problem I am experiencing (and then right after to the bank next door to take out a new loan when I'm told all the electrics need to be replaced), I wanted to tap the experience on this forum to maybe get an idea of what the problem may actually be.

I own a '91 normally aspirated MR2 with about 80K on the clock. Just recently I've been seeing the battery indicator light up and when this happens the volt meter also pegs out at the top. At night when this happens the headlights get noticeably brighter also. This situation happens intermittently and when it happens all of the above takes place, after a short period of time the battery indicator goes off and everything returns to normal. There doesn't seem to be any pattern as to when it occurs.

The car starts right up so I don't think it's the battery getting weak. I'm thinking that it might be the alternator or voltage regulator (hopefully it's limited to one of those).

Am I right in thinking that it's likely the alternator or voltage regulator or is this likely something more serious?

I appreciate any pointers regarding this.

[Ben]

Its probably the alternator. When the battery light turns on and the volt meter tops out, that is the alternator going to full output, hence the reasons why the lights get brighter.

I would still get you battery tested, its free at a lot of parts stores.

[Gairloch]

If you have a Sears around you I know they've got the ability to check the entire charging system.

[shiftless]

I'm a bit relieved to know it's probably just the alternator, although I will have the battery checked out first just to make sure it's not that.

You would think though that when an alternator fails it would show a lower voltage output not a temporary high voltage output. But I know as much about electrics as I know about nuclear physics.

Also, I wonder if keeping the battery on a battery tender most the time has an effect on the life of the battery. The car doesn't get ridden all that much so I tend to keep on on a battery tender. I guess though it's better then letting the battery run down on it's own though.

Anyway, thanks for the info.

[HeartbreakMR2]

Originally Posted by Gairloch

If you have a Sears around you I know they've got the ability to check the entire charging system.

I have seen times when people would take their cars to a parts store for testing and pass the test. Then go to sears, and find that there was a problem with the test performed at Sears.

Side note: I hate Sears so this is not a promo for Sears, but did work their for a short time and wanted to pass on my exp.

Purchased a new alternator for a parts store, installed it (while working) at Sears. Tested bad. Had a terrible time returning the part do to it testing good at the parts store. Ended up having the old alt. rebuilt and it has worked great ever since.

Oh note: (On the bad new part) I noticed the dash reading was lower then I felt it should have been when I pulled it out. It was not tested completely until I made that observation. So if that is the route you take just ck your readings before you leave. Some managers push the tech to push cars out resulting in cut corners.

[Ben]

Originally Posted by shiftless

You would think though that when an alternator fails it would show a lower voltage output not a temporary high voltage output. But I know as much about electrics as I know about nuclear physics.

The reason that it is spiking high is probably because the battery is failing, not so much the alternator. But as mentioned above, Sears will test it all for you.