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Alternator died upgrade options

2163 Views 8 Replies 6 Participants Last post by  CELICA XX
Alternator died upgrade options

Ok so I'm on my way home the other night stopped at jack in the box at about 2 am. While I'm sitting in the drive thru the charge light and e-brake light come on. I'm like "great I know what that means" dead alt.
So I manage to get home the warning lights flickering off and on the whole way home.

So her is my dilemma I have the alt from my old 85 but was hoping not to have to use it. I want to upgrade the alt (65 amps is just not enough). I've done a search and come up with the following
1. I could use the 80 amp alt from the mkIII if I modify the mounting bracket its a direct fit
2. The 100 alt from a mkiv will work all that need changing is the bracket mod and switching of the alt plug.
3. The mrII early 90 model 100 amp alt could be used and since its a direct swap to the mkIII i would think that with the bracket mod would be a direct fit into the mkII

I am leaning twords replacing the alt with the 100amp mrII model. 100 amps and no need to change the plug. What I need to confirm is that the mrII alt will fit.

Any one here using the mrII alt?

Comments suggestions welcome


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Ok I broke down and just put the one I had lying around in. The supra is my only car and I live out in the boonies.

I'm not deterred I WILL put in a better alt. With every accessory on I still get voltage reading under 12 volts. With a 700-watt amp and the toons cranked she gets really low.

Help anyone used the 100apm alts?

Someone else would have to chim in but I didn't know about the MR2 one. I am using the MKIII unit with the 5M pulley on it.
I took my 84 alt to a place here in Eugene called J&S Alternator and Starter Supply and had them rebuild it to 100 amps. It works great and was $150. All my accessories and 400W of PIAAs on at a 700 rpm idle volts drop to about 12 between 700 and 1000 it jumps up to ~14.4. So still not full 100 amp at idle, of course, but I don't know how the mk3/MR2 alternators are at idle either.

I got a 135 amp alt. for $195 shipped. Works great with all my extra lights and stereo equipment. I'm running a 150 watt 6 x channel amp. With no cap on it. New 135 amp alt. powers everthing just fine. Check out their website here
I've herd that if you build a alt for higher off idle amps that your at idle voltage and amps suffer is this true?

If I do end up using a 7m alt how hard is it to just switch the pullys?

Thanks all


If you want to use the 5m pulley on the 7m alternator you will have to find a machinist to hog out the shaft hole on the 5m pulley as the 7m is larger diameter. My machinist friend is in Arizina for next 4 months or else I would have him do yours. HTH
supra_toy said:
I've herd that if you build a alt for higher off idle amps that your at idle voltage and amps suffer is this true?

Mine is better at idle then the stocker used to be....way better, but still not full output, of course. Neither was the stocker at idle. I don't have to rev hardly at all before the volt meter jumps to the right. 800 - 1000 rpm is full output range.
The mechanic I have been taking my car to, apparently is putting the cheapest quality alternators in. It has been replaced 5 times in the past 3 years. Voltage Regulators, dioads, and other various problems. I would have been better off with a Toyota part.
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