Voltage spikes!!!!

[Blindedlegacy]

Brakes, turn signals, blower motor, electric fans, all of it is causing a sudden voltage spike and I don't even know where to begin it check for it.

[Blindedlegacy]

Originally Posted by Blindedlegacy

Brakes, turn signals, blower motor, electric fans, all of it is causing a sudden voltage spike and I don't even know where to begin it check for it.

Didnt mean to say spike. Its more of a drop. Could this be a bad voltage regulator?

[CanadianBak'inSupra]

test it with a multimeter aswell as your alternator.
a high output alternator may be the answer.

[CanadianBak'inSupra]

test your battery as well.

[Blindedlegacy]

Originally Posted by CanadianBak'inSupra

test your battery as well.

It tested good too
Also the starter

[CanadianBak'inSupra]

i cant even remember where the regulator is and i cant find it in the manual.
did you test the alternator??

[Blindedlegacy]

Originally Posted by CanadianBak'inSupra

i cant even remember where the regulator is and i cant find it in the manual.
did you test the alternator??

Its on the back of the alternator. And the alternator is putting out 14v

[cre]

Voltage isn't an absolute diagnosis. I'd pull the alternator apart, check the collars for excess wear and replace the brushes. At idle the electrical system may run at a deficit due to the small size of the alternator and age of the overall system... It's a fairly common complaint and the battery should compensate for the most part. Some people swap in an alternator from a turbo MR-2 which is 100A or 110A... I think it's just 100A (I'd go look at mine but it's hell to get at on the MR-2.

Another thing which can cause headache is old style, wire type fusible which have begun to degrade. These were used regularly up until 87 or 88 and then intermittently (until Toyota ran out I guess) into even 90's models. If you look in the engine compartment fuse box and the 100A fusible link doesn't look like a large plastic fuse but rather just a large piece of wire you should try replacing it with a new one (you can use a sealed style one, it bolts right in).

Then just start pulling and cleaning all of the major cable connections.

[Blindedlegacy]

Originally Posted by cre

Voltage isn't an absolute diagnosis. I'd pull the alternator apart, check the collars for excess wear and replace the brushes. At idle the electrical system may run at a deficit due to the small size of the alternator and age of the overall system... It's a fairly common complaint and the battery should compensate for the most part. Some people swap in an alternator from a turbo MR-2 which is 100A or 110A... I think it's just 100A (I'd go look at mine but it's hell to get at on the MR-2.

Another thing which can cause headache is old style, wire type fusible which have begun to degrade. These were used regularly up until 87 or 88 and then intermittently (until Toyota ran out I guess) into even 90's models. If you look in the engine compartment fuse box and the 100A fusible link doesn't look like a large plastic fuse but rather just a large piece of wire you should try replacing it with a new one (you can use a sealed style one, it bolts right in).

Then just start pulling and cleaning all of the major cable connections.

there you are to save the day. i have a little bit more info. when i press the brakes it goes down to 12v but after that initial drop if i were to press it again it BARELY moves. every other electrical load is similar. now if i do swap in that alternator will it fit in or do i have to do some fabrications and what year mr2

[cre]

The swap would be a bandaid, nothing more... You still wouldn't have fixed the real problem. Unless you've got the heater running on full and the headlights on you shouldn't see it dim significantly when you step on the brakes... a little isn't surprising. Start with the basics first (It's MUCH cheaper too). Regardless of the voltage you're seeing you should take the battery to a shop for a complete battery test (charge/discharge); It takes about an hour so you'll need to drop it off. There are home chargers which have testers built in, the method and accuracy with which they test varies significantly so I would read reviews and don't cheap out. IMPORTANT!!! If you have an AGM (Absorbed Glass Mat) battery do NOT connect it to any charger which does not specifically have a setting for AGM!

The only time I really recommend a larger alternator is if the electrical load has been significantly increased placing demands on the charging system well beyond the original specs; Huge amplifier, electrical fan conversion, electrical cabin heater or an old battery with a bad cell or two. The only other time I'd consider it is if it's a city car where it sees lots of short trips and the battery probably isn't charging enough.... My wife goes through about a battery a year if I don't keep on it with a charger every few weeks.

No, the MR-2 isn't a straight swap in but I think it was close... Something like swapping the pulleys, maybe the wiring pigtail and a washer.

I highly suggest you fix the real problem though. A larger alternator still may not remedy the symptoms.