19rxseven87

Hi guys,

So my alternator wasn't holding a charge before (after i installed an aftermarket stepper motor boost gauge) and thus I changed the alternator.

The alternator seemed to help the problem only a little.

The alternator will charge, but the battery will only stay at 12 volts when running.

When I shut off the car and re-start the car, the battery will read 8-9 volts until I step on the gas then it bumps up to 12.5 volts.

I have regrounded the wires to the main negative to chassis and to the strut tower ground as well as grounded a new wire to the alternator. I've changed the battery terminals to different ones (since the negative ground broke off)

I have no idea at this point what to do?

I've also re-soldered the cpu as well as the idiot light cluster and wiper switch cluster (shouldn't have affected anything). I've also added an aftermarket alarm and aftermarket dash.

Any suggestions as to what to do? I don't think that any of the aftermarket stuff that I have added contributed to the alternator not charging properly.

mazdaverx713b

iTrader: (91)

first off, the alternator does not hold a charge. it supplies the necessary voltage for the vehicle when running and keeps the battery charged. at this point, i would pull the battery and the alternator and have them tested at your local auto parts store. sounds to me like the battery has taken a turn for the worse. i would also check your battery cables and make sure they are good. test for continuity of each, inspect them for splits or corrosion, and ensure your grounds are clean and secure (see link in the FAQ at teh top of the tech page).

the aftermarket alarm, if installed improperly can cause a battery drain. did you install it or did you have a reputable company install it?

19rxseven87

i understand that the alternator doesnt hold a charge, and only charges the battery for it to hold a charge.

i installed the aftermarket alarm, but i know it isn't causing a battery drain (because before i installed the gauge, and new terminals the alternator was charing just fine)

as for the ground, i used 8 gauge thick (rockford fosgate) wiring and grounded to oem ground points, to the main chassis ground and to the shock tower ground as well as to the alternator.

I have had the alternator and battery tested at autozone, and it read that the alternator was good as well as the battery. i even replaced the battery and the problem was still there. the battery cables are good because of the fact that i added a new 8 gauge wire to the stock grounding points thus the stock wires should have no negative effect if it was the culprit.

as for a battery drain suggestion, the battery doesn't charge at 14 volts while driving, so that rules out the battery drain suggestion.

do you guys think a bad ecu ground would be the culprit or just bad ground and positive terminals (they aren't the best...)

i'm going to go to walmart right now and buy some new terminals and lets see how that goes.

any more suggestions? (thanks for inputmazdadaverx713b)

mazdaverx713b

iTrader: (91)

maybe the voltmeter is faulty. have you tested the alternator output with the engine running using a multimeter? same for the battery. put a multimeter on it with the engine running?

19rxseven87

i havent checked that, but i will.

mazdaverx713b

iTrader: (91)

hopefully it wil lhelp. you know, 20+ year old gauges can go bad. the oil pressure gauge on my 10AE has a mind of its own.

satch

iTrader: (1)

Read post #8 in the following link but disregard the last sentence.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/help-i-have-no-power-anything-904245/