Matt B
Matt B Dork
1/30/12 10:45 a.m.

Hey everybody, I'm having a somewhat weird issue that I think may be a failing alternator. Although feel free to correct me or brainstorm with me if I am wrong. I'm just looking for a little confirmation before I start buying up parts.

The car in question is my 86 MR2 and it has the original 16V 4AGE. Under hard braking and sometimes sitting & idling, the brake, battery charge, and cooling fan warning lights will come on briefly and go back out again. This does seem to effect my battery charge gauge while it's happening (needle gauge, separate from the warning light).

I've checked for the usual culprits, loose wires around the alt, battery, etc. but no dice. The alternator was used when I installed it a couple of years ago, so it wouldn't surprise me if it was finally on it's way out. I remember having a similar situation with the dash lights at that time, but I thought there were more of them the first time the alt went out. I think I described it as "Christmas on the dash".

Anyway, thanks in advance for the input.

Dr. Hess
Dr. Hess SuperDork
1/30/12 10:49 a.m.

Alternator. The brake and charge light are hooked together on Toyotas of that vintage. I dunno about new ones.

mad_machine
mad_machine SuperDork
1/30/12 10:57 a.m.

I like the fact that it has a cooling fan light.. I may have to add one of those to my cars (they have electric fans)

Otherwise, I either agree with you about the alternator.. or you have a bad ground somewhere

Matt B
Matt B Dork
1/30/12 11:25 a.m.

Thanks for the quick response guys. Alt is looking like the culprit, but I appreciate the tip on the bad ground, as I haven't checked that yet. That might also explain why it's affected by inertia.

Anybody have luck with reman'd alternators? Rockauto carries a Denso model at a reasonable price.

Matt B
Matt B Dork
1/30/12 12:52 p.m.
mad_machine wrote: I like the fact that it has a cooling fan light.. I may have to add one of those to my cars (they have electric fans)

The mk1 mr2 seems to have a couple of gauges-n-lights you don't see on many cars these days, including a oil-pressure gauge and the aforementioned battery charge gauge.

Dr. Hess
Dr. Hess SuperDork
1/30/12 1:27 p.m.

I dunno. My AE92 haz those.

I've had OK luck with reman alternators. My professional wrench friends say NAPA >> O'Reilley's >> Autozone. Dunno where RockAuto fits in there. You take your chances. Might also look on Amazon. I've had good luck with auto parts on there lately.

Matt B
Matt B Dork
1/30/12 1:33 p.m.

Well, the AE92 is still pretty close to the AW11 in build and vintage. I'm not surprised they had those gauges too. Not a big deal either way, just a passing observation.

Turns out I can get a reman'd Toyota alt for about the same price as the Rockauto stuff at Lithia Toyota of Springfield. They have the best online prices for oem Toyota stuff that I've ever seen personally. Plus Aaron over there has a AW11 and can identify many weird and/or discontinued bits that are hard to explain to the average parts guy. HUGE thumbs up all around for his help and advice.

That said, I may replace the brushes before I buy a whole new unit.

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