why the battery discharge light is on occasionally?

[surfun]

This is for my 91 MR2: Just as the title says...my discharge light comes on...maybe 2/3 of the time to be exact, but it flickers off and on. The odd part is that the volts are always the same, and there is no effect to this...headlights, backlighting, etc are all stable while this is on and also during flickering.
Normally I would just assume I need a new alternator, and slap a cheap reman on (if it were a 5 minute job like my previous RX7), but since it is not exactly an easy swap, I thought I would ask if anyone knew of any other possiblities first...experience is power!
Any help is highly appreciated!

[OEMonkey]

first check connections at the battery and alternator. load test the batt. then monitor charging v and see if it does go lower when the light flickers on.

[surfun]

I have cleaned the battery connections to perfection so I know it isn't that. However, I have not done anything to the connections at the alternator...
As I mentioned above, the voltage doesn't move a bit when the light comes on...but I will try it again tomorrow with my DMM to be sure.
I guess I could also pull the battery off and drag it to Advance...it is one of their store batteries. I didn't suspect the battery because it is quite strong...but I guess anything is possible.
Anyway, if it does come to having to remove the alternator, and at least have it tested, what is the procedure, or is there a sticky somewhere telling me how.
Naturally, as I said already, the lack of access to it is the reason I didn't simply pull it off in the first place and take it for testing, but will if nobody has any other ideas.

[el niño]

how much is the alternator charging?, start the car and put the voltmeter across the battery posts, it should read between 13.9-14.2, anything below is a sign of an altenator going bad.

[Tercel GTS]

the voltage regulator could be intermitting, or the brushes may be wearing out
there is a sticky in the tech section explaining how to replace the brushes if so.

[91MR2NASTL]

The same thing happened to me with the battery light flickering on and off, i made the mistake of ignoring it thinking it was battery terminals. the alternator finially went out and i was stuck with a lifeless mr2 in rush hour traffic in the middle of an intersection. you dont want that lol check the alternator

[surfun]

Yes, I agree, but the funny thing is that the previous owner said it had been doing this for a couple years with no ill affects. Heck, I have put roughly 1000 miles on it like that so far. You are right however, and I would hate to get stuck somewhere when I was too far from home to drive back with no alternator.
Also, after pricing alternators for this car, plus considering how difficult it looks to remove from this car, I was hoping there might be another alternative!

[91MR2NASTL]

removing the alternator is the biggest pain in the ass ever. you have to have someone try to pry the engine up as you yank it out, or just get so pissed after you ahve been standing in the rain for 2 hours and just pull as hard as you can lol.

[surfun]

The last alternator I changed was in an 89 RX7. If you have ever seen the engine bay, you know the alternator is the top front / center item. There are 2 bolts and it comes off. The actual time to remove it and reinstall another one was roughly 5 minutes, and that counted taking my time and adjusting the belt tension a couple times. But I fear this job already -
Before I start removing the alternator however, let me ask a couple questions...
When you say you had the same problem, was the light that was coming on with your car the discharge light, or the alternator light. If I am not mistaken, the car has both...
My problem is the "battery discharge" light comes on, but no other light. Question two is did your car have cruise control? If you ask why I would ask such a question, someone told me on another forum that MR2's without CC (like mine) are easier to remove the alternator. I have no idea what that has to do with anything, but this is what I was told...possibly a bunch of BS...but I thought I would ask.

[surfun]

By the way, I checked the voltage today, and it is virtually the same (13.5 I believe) when the light is on or off. Anyone have any ideas?

[91MR2NASTL]

lol cruise or not, the alternator is on the bottom of the engine. thus a major pain in the ass to get out.

[OEMonkey]

Originally Posted by surfun

By the way, I checked the voltage today, and it is virtually the same (13.5 I believe) when the light is on or off. Anyone have any ideas?

If charging system is normal at idle and under load, then the wire leading up to the dash light might be getting grounded intermittently on the chassis or wherever causing it to light up prematurely. I have an aftermarket voltmeter gauge so I can monitor and notice any charging system abnormalities. How's belt tension and alt pulley?

[jackcannibal]

Bah, this is old school stuff. Mazda and older Toyota cars all did this when the alternator was going out. Get yerself an alternator and be done with it.



Also, 13.5v is not that great. Should be 14.6v.

[jackcannibal]

Oh yeah, use a block of wood and floor jack to move the engine up from underneath. Really not that nasty.

[MitchB]

Some people like to remove the alternator from the top. Without cruise control, it's possible. Cruise control makes it impossible unless you remove the cruise assembly.