LocostUSA.com

I am building a Locost using a 1999 Miata. The car is now running well and drivable, but my instruments indicate that the car is not charging the battery. This seems to be the case, because the battery has to be recharged periodically. I have had the alternator tested and it's OK. I was told that the computer helps regulate the charging of the battery, but I don't know where to go from here.

Could it be a simple ground issue? Any help is welcome.

Thanks,

Scott

If you hacked up the wiring harness you might have screwed up the connection from the ECU to the alt. There are 2 wires from the alternator that end up back at the ECU. If I recall correctly, one of them was routed to china and back. Seriously it went from the alternator, to the back passenger side, over to the driver side back forward and then across the dash and back to the ECU. It would be pretty easy to screw up that connection. Especially since it was in multilpe the wiring harnesses (engine, rear and front I think).

Don't rely on ther light. check the voltage at the battery with the engine running. It should be over 13 vdc. If it is, then the alternator and regulator are working.

The regulator appears to be built into the pcm.

The charging bulb has 2 connections. For current to flow across the filament, there must be a difference of potential/voltage across the bulb. One side connects to the battery, the other connects to the alternator output. If the alternator is charging but the battery side is not well connected, the light will have a difference of potential and still come on.

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Miata UBJ: ES-2074R('70s maz pickup)
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LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Thanks guys. I'll let you know if I make progress.

Problem Solved! After running several connectivity tests, I found that the Gray/Red wire running from the alternator was dead. After reconnecting to the computer, the battery is again receiving charge. I'm getting about 14.2 volts at the terminals.

Thanks for the help!

Scott