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Alternator will not charge??

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Old 01-05-11, 10:21 PM
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Alternator will not charge??

So my brother has a 1988 convertible with a microtec. it has a s5 alternator. The only way it seems to bump the voltage is if he revs his car up to 3.5k right on start up. We were wondering if anyone knows how to wire up the alternator so we won't have to rev the engine right when it turns on.
Old 01-06-11, 10:11 AM
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Check the 2nd gen FAQ for the FD alternator wiring diagram. S5 wires up in the same way. Your issue is that the 2 pin connector at the back isn't receiving voltage on the appropriate pins.
Old 01-06-11, 12:23 PM
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https://www.rx7club.com/showthread.p...=fd+alternator

Originally Posted by me
There's also a nice diagram in the FAQ: https://www.rx7club.com/showthread.ph...72#post5131072

1) The wire that used to run to the R terminal of the S4 alternator gets capped off, and a fused constant 12V power wire is run to the new S terminal on the S6 alt.
2) The L terminal wire stays the same.
3) The B-posts can be swapped to match the S4 ring terminal, or a new one can be soldered on.
4) The pulley has to be replaced with a v-belt pulley intended for the S6 alt. An S4/S5 pulley can be milled out to accept the larger shaft, or an aftermarket pulley can be sourced. Correct pulley size is approx 45mm ID.
5) If you get an oversized pulley, the belt size needed will increase.
6) A new bolt & nut will be needed for the tensioner bracket, since the S6 alt does not have threads in this location.
Ignore 3 through 6. That's for an FD alternator.
Old 01-06-11, 04:06 PM
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dude check your battery cause my battery was bad and my alt was good and we thought it was the alt but tested good.. i had it charged i could start car and everything but wouldnt stay charged.. so i took it to the auto store and they tested both for free so yeah thats my input what it could be never know could be a bad battery...
Old 01-08-11, 06:53 PM
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Originally Posted by JDMFC3S TII
So my brother has a 1988 convertible with a microtec. it has a s5 alternator. The only way it seems to bump the voltage is if he revs his car up to 3.5k right on start up. We were wondering if anyone knows how to wire up the alternator so we won't have to rev the engine right when it turns on.
One thing that Pops out is that the alternator does not Charge until 3500rpm..Have you checked the Belts to see if the pulley is just slipping?.
If you just recently changed to an S5 alternator then you need to Feed one of the Connector Pins on the alternator with 12volts.
The other wire goes to the Gauge,and that is white black(i think) on the harness.(please confirm before wiring this up)
Do a search on Forum..look for S5 alt Swap..they will have a diagram with ALL the alternators and woring schematics of them..It shows HOW to hook up the s5 alt to the S4 harness.
Old 01-08-11, 09:02 PM
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If the regulator isn't being powered properly, the alternator will need to self-excite to begin charging. That means spinning at a high enough RPM. That was my take, and it sounds like what Aaron was thinking too.
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