Charging Problems

tulsan87 · Mar 15, 2012

Hey all I'm new to this forum. I also have an account at another mustang forum but I can't seem to get any definite help on my problem (nothing against them I just thought I'd try here too). I have a 1987 Gt convertible 5spd. My problem is this... I can charge the battery, start the car & it's good. I let it run 10 - 15 min, turn it off then try to start again & nothing happens. I believe the battery is not being charged. With the car running the battery meter on the dash is above halfway, when I try to restart it's low. Here's what I've done so far... I got a 3g alternator from a '94 mustang w/ a regulator plug, post for power to battery, & a single plug. Here's how I hooked it up... Battery cable wire (4 ga) from positive side on starter terminal to 175amp mega fuse. Ran another battery cable wire from that to the back of the alternator. On the regulator plug I wired the white back to original white, green to original green, & yellow to alternator post. The wires from the old rectifier plug I took the 2 or/bl wires & put them to the alternator post & the original white wire to the single D shaped plug on the alternator. That leaves just the factory yellow wire to the regulator unused. I've also had the battery tested at an auto parts store & it tested good (could it still be just bad enough not to accept a charge? What about the starter? If it's going bad can heat prevent from starting? When I try to start it doesn't do anything, which is why I think it's a charging issue. The meter on the dash goes up a little when I put the key in but I can tell from the reading that it's low. Now I'm just rambling cause I'm frustrated haha. I'd appreciate any help! ~Q

jrichker · Mar 15, 2012

Alternator is wired incorrectly.

3G alternator installation:
Do not disconnect the black/orange wires from the starter solenoid. If you do, the yellow regulator/field current wire will not have a voltage sense source for the regulator or alternator field windings.

Alternator wiring