I am having a battery charging failure from my alternator on my 99. I have been eliminating everything on the wiring diagram found here:

http://www.mellens.net/mazda/mazda_m...999_wiring.pdf

This diagram im noticing is a little different than my car not sure why but it says the ecu is on the right side of the dash, no where does it list the ground in front of the diff. and a few other deviations.

I have tested for continuity on all wires except
(i have not been able to find in my car based off of my schematic)

1. to the ecu from the alternator
2. to the alternator from the ecu

In my car at least one of these wires trace back to the fuse box in the engine bay and not straight to the ecu like the diagram would suggest.

I have done the following already:

brand new battery

new belt

reman alternator that has been bench tested properly

all grounds have been taken apart and cleaned

I have a newer megasquirt pnp 2 that i hope is not the culprit of my alternator failing and would like to rule out everything else first before purchasing a new one. (unless there is a better way to bypass the ecu regulator)

Is there a better diagram i should be using for my car to track down voltage drops in the line or do i need to bite the bullet and start looking into a new ecu?

Any help would be awesome i have an event coming up in a few weeks and need to get this motor broken in asap

 

That wiring diagram does not show all the connectors in the car. Find one from a factory service manual. There is a connector built into that fuse block and one of the alternator wires runs through that connector. IIRC, the other wire runs all the way to the back of the car and then comes back down the driver's side to the ECU. Never understood why.

 

that makes sense thanks!

 

There's a connector behind the passenger seat, under the carpet. I disconnected that when I installed my rollbar and didn't properly reconnect it. No charging condition resulted. Took me half a day to find.
Did you take a voltmeter to the output from the MSPNP (I think it's 1O)? This should read a positive voltage. If you're not charging, it should try and peg the alternator, so you should either see 12V or 5V, depending on what it's using for a pull-up.

 

I'll check that connection. I'll also check the ms pnp out voltage see what I'm getting. I just assumed since the alt. Tested fine and new battery and belt it had to be something in the wiring or ecu.