hey guys... my alternator is not charging my battery. ( both brand new) anyways i checked the two white/black striped wires from the harness that goes into the alternator from the back (w/ a test light) anyways one of them is good and the other one i hear a weird noise and dont get power with the ignition on. anyways i heard somewhere they both shoudl have 12 volts coming out and that each have a fuse. well guys were are these fuses? any clues? also is my info i got correct?

 

please guys thanx!

 

The only fuse for the alt is the 80 or 90 or 100 amp main fuse in the underhood fuse box.

The other two wires on the alt are the voltage referance and alt output wires. Putting a test light in them can blow out the internal diodes depending on how you hooked the test light up. If you blew the diodes, go get the alt rebuilt.

 

i just gto it yesterday and today i got it checked and it read 15 amps... if my 80 amp fuse was blown wouldnt teh car nto start at all?

 

On the S4's, the upper black/white wire is fed by the 15A "engine" fuse, and should be powered with the key on...

The white/black wire on the bottom is powered by the 7.5A "meter" fuse, but the voltage may be less than 12 due to the resistor in the alt warning light relay, which is part of the circuit...

 

thanx wayne u da man... i did check the 15a fuse it seemed fine though... umm if is not the fuses... then why isnt it charging any clue?

 

First of all, how have you proved to yourself that she's not charging?

Put a meter on the battery posts while idling. Anything over 13.5v or so is considered good.

If all you're getting is battery voltage at the battery while running, remove the rubber boot on the top alt terminal, and read it for voltage, to ground. If you all of a sudden have good voltage now, then you have an open between that alt terminal and the splice-in to the positive batt cable near the fuse box...

If you're not getting anything over batt voltage at that alt terminal while running, then the alt may be bad...

 

well earlier today... it read 12.4 volts from the alternator ... and my gauge indicated 12 volts ( i have no radio) i went to test the alternator.. i took it off the car and it read 15 amps... in the advance auto parts tester... my battery gauge use to indicate 14 volts all the time then all of asudden it died whe i installed a radio ( i took it off now but maybe i blew something) ( also at advacne auto parts when they tested it they told me they werent getting a reading from the alternator to the battery meaning it wasent charging the battery

 

Next question has to be which circuits did you use for the radio?

Usually guys blow the "illum" fuse when installing new decks...

 

If it's not obvious, there is no fuse in between the alternator and the battery.


-Ted

 

Yes there is, it's the 80A or 100A MAIN fuse.

 

tru tru... I went to some rx7 specialist (LOL) and he said it was the alternator and that even though its 2 days old i might of blew it out since my other battery had 8 volts... u guys think thats podssible?

 

Do you have a pic of the schematic?
I swear my '87 does not.
I had to redo the wiring due my battery relocation, and I swear the smaller gauge wire went from the + positive battery terminal straight to the alternator post.


-Ted

 

Here's a genuine, error free, Mazda 1987 FSM diagram.

 

it was the alternator... i replaced it and now its right at 14... maybe alil very tiny bit above it... yet im still scared to install my cd receiver because i think is gonna drained it again... anyone knows how to wire the power source for the fc?

 

Anywhere from 14.0-14.5V means the alternator is charging is fine. You will have no problem installing a stereo, because there'll be little to no difference in power draw compared to the stock stereo. I'm running a 200W amp on a stock charging system with zero problems.

 

do i have to conect the power wire and join it with the constant 12 volts wire? other wise it wont power up the cd reciever...

 

Head units need two power supplies, a constant supply from the battery and a switched supply that's live when the key is in the ACC or ON position. These need to be connected to the appropriate wires in the stock stereo loom. This wiring info has been posted many times before so do a search for it.