lookin4astang

Ok, I've been working on this charging issue for a couple of weeks now with no luck on my 87 GT. I started by replacing the alternator and battery with new ones. Both were bench tested before hand and are fully operational. I then bought a new plug for it since my plug was missing its clips. Made all the new connections and am reading the correct voltage at the plug when the car is idling. But it isn't charging. So it's getting out of the alternator, but stopping somewhere before it reaches the battery.

I've went through the wiring harness following each wire from the alternator, and so far have fixed any wires that have been bad. The voltage regulator is built into the alternator btw. I honestly have no clue where to go from here.

In my wiring diagram, it does show the two black/orange wires merging into one single dark green wire which is connected to the relay. Mine didn't have a green wire connected to the relay, so I found one in the wiring harness that was cut off right at what appears to be a 14 ga. fusible link. So, I put an end back on it and reconnected it to the relay to test it. Nothing happened.


Here is the diagram I am using. Does anyone have any idea where I can go next? I'm all out of options at this point.



I really need to get this issue fixed so I can move on to other issues. My truck might be down for a while, so I'm gonna need to make this thing my DD within the next few weeks. Anyone happen to have pics of all of this and had this problem before? This is on a carbed 351W that the wiring harness was butchered on. I've gotten a lot back together, but this is the main problem I have left. The charging system is the same as the 5.0 on mine, so shouldn't be an issue there. I've been told to check the fusible links, but how can I tell if they are bad? Just looks like a piece of rubber to me. None are burnt looking or broken either.

hammeron

i would be interested in knowing what voltages you
have at points a & b. have someone rev the car up to
say 2000 rpms while measuring (i'm not sure your idle
rpm is high enough for charging).




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lookin4astang

I cant tell my idle. My tach doesnt work. Where is the best two places to check and I can let you know tomorrow. My damned multimeter is one of the cheap analog ones.... Not real sure how to use it correctly.

hammeron

your volt meter will work just fine. just put the black lead
on the negative post of the battery and put the red
on point a (rev engine) take reading.

do the same thing for point b.

make sure the meter is set for DC volts and the range switch might
be something like 0-30

you can use a 9v battery to set up your meter, before
getting it close to the engine bay

93must

Are you sure your belt tensioner is good and the belt is tite enough. Sometimes when the belt is loose at high rpm it will slip and not turn the alt fast enough? MY .02

lookin4astang

Yep. No tensioner on this one. The alt is on an adjustablebracket. And its good and tight.

lookin4astang

Ok just got in from checking everything. It's odd. I must have cranked this car 50 times and let it run since I swapped alternators. It still fires up just fine like there's no charging issues. I put the meter on the battery and no matter what setting I had it on, it didn't read anything. Battery is good, and if it's switched to ohms, it pegs out.

I also have a tester that checks the battery and alternator. The battery (when car is off) shows it's fully charged. The alternator (when running) shows nothing whatsoever. (I stuck the positive end in both black/orange wires and also every other wire) I checked this tester on my truck and it works perfectly.

I dunno what to do next. My voltage gauge in the dash reads just above the red like it isn't charging. There is an aftermarket voltage gauge in the dash and it reads nothing. So I'm not sure where to go next. I'm still not absolutely sure what the green wire with the 14 ga. fusible link goes to. I connected it to the starter relay (saw one on the diagram like it) and nothing happened.

Any more suggestions? BTW.... the only other gauges that work in the dash is the speedo and fuel gauge. I'm fairly sure the stock gauge is working because it comes up when I turn the key over. Oil pressure, and water temp are monitored via aftermarket gauges in the dash.

IF the old saying is right on oil pressure being 10psi per 100 rpms, then I am idling about 600 rpms (60 psi). It started idling up once the car warmed up to about 75 psi (Im assuming 750 rpms if all is correct.)

hammeron

it sounds like the multi-meter might have an internal
fuse that's blown.

it's difficult to troubleshoot electrical issues, without
a working voltmeter. it may be worthwhile to
get a cheap one, from radio shack or other
electronic parts store.

lookin4astang

I did some reading up last night on my issue. The forum I was reading at said you are supposed to have the white/black wire connected on the starter relay to the post with the I on it. My relay has 4 posts. Two on the side like normal, and two facing the engine. One has the red/green wire from the disty on it, and the other just has an I above it and nothing hooked up to it at all. I=ignition according to that thread, but my car cranks fine, and everything works fine outside of that.

I also checked my voltmeter, and all the fuses inside of it are in perfect working order. As I said it works when it's flipped over to ohms. I've never been able to use one of those damn things right, so I dunno. Im getting ready to go out of town, so no time to go get a new one until I get back.

vt89gtvert

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