Ok. I'm having difficulty diagnosing this and a search shows no one with problems that can aid me in fixing this. Here's the deal, my car is having charging problems. I've had the battery, alternator, and starter tested by 3 different stores and they all check out fine. This is good, since they are all less than a year old. Starter is 6 months, alternator 9 months, battery is 2 months. All puchased as new, not rebuilt.

What my car is doing: When I start my car, it's hard to start, acting like it doesn't get gas at first. Once it fires it's fine. It may take 20-30 seconds to start, which I do in 5-10sec intervals. Once started, it shows just under 13 volts on the dash, the moment I touch the accelerator, or change gears, it drops to just under 12 volts.

If the ambient outside temperature is cooler (around 50-60) it will act as if it's running off the battery, and yet will run fine until I shut the car off. Once I go to restart, it shows just under 12, and the next will be almost in the red on the dash, and frequently won't start by the 3rd time I've started it after a full charge.

If the ambient outside temperature is in the 70's (I love Florida sometimes), it will slowly creep up to just under 13 volts as the temperature of the engine reaches normal operating temp. It's not sudden, but gradual. When it's acting this way, I can start it 5 or 6 times before the battery starts to get weak, up to 10 before it's dead.

If it's dead, and I get a jump start from someone, it will stay almost exactly where the needle was when our cars were connected. I use the chassis as a ground, not the neg terminal, as it states in the Chiltons.

As per service codes, none have been set. The only other thing I've noticed is that when it's warm outside, I can notice a decent change in the needle when the engine is at different RPM's, yet when it's cold, it doesn't show the same response.

As per what's new: alternator, starter, gas pump, water pump, power steering pump, plugs and wires, battery and bolts, TPS sensor, fuel pump relay, fan, fan relay, IAC valve, MAF sensor, and many other parts, mostly mechanical. The only modifications done is that someone that had the car before me removed the clean air intake and associated pumps/valves, and removed all stereo equipment. (Which I plan on getting should I ever fix my charging issues.) I also had a problem with the old alternator not charging, and replaced it with the new one, when I still had nothing, I took it to a specialist that went through, at my request and while I was present, and replaced all the ... the word is escaping me right now....... small wires that act as fuses.... well I'm sure you understand what I mean. They all appear to be in good condition still. I've also noticed a very significant drop in voltage when the headlights are on, which isn't present when the parking lights alone are one. (Just under 13 volts becomes just under 11ish, yet the alternator seems fine. Once the engine has warmed up, this difference goes away, and becomes the normal small drop of the needle.)

If anyone can point me in the right direction, I'd be most appreciative, as this is pretty much my final problem with getting my car in good working order. I've traced wire after wire, and cannot find any that show signs of being 'the one'. Since I don't see any spikes or drops in voltage that show a loose wire, and can't find anything actually wrong, I'm at wits end.

edit:
1985 IROC TPI Auto PS/PW/PL 5.0 Engine 'F'

 

Does your "Choke" light come on when you turn your key on with the engine off? (Not that you have a choke - but don't get me started)

If not, try replacing its light bulb.

 

if the choke light comes on replace the alternator (if u have a choke light) i had the same problem and my alternator was bad but tested good some people test it reaterdedly with a volt meter i could do that at home

 

The situation I described was if the "Choke" light does not come on with the key on & engine off. The circuit that carries ignition current to the alternator goes through the bulb; so if the bulb is out, the alternator won't "know" that the ignition is on, and it won't "know" to charge.

If the "Choke" light comes on with the key on and the engine running, then it's telling you the alternator is bad.

 

get a multimeter and check your wires resistance.
check the Baterie negative to the engine, check the postive from bat to alternator...

it's not charging enough that for sure.

I had a car this week for an alternator that Charged too much (a chrysler) anyway, it had 2 broken "Fuse wire", and 1 was the wire that tell the baterie voltage to the Ecm... so it made the alt charge too much. Then after we checked the negative bat to the intake and it had WWAAYY to much resistance, it was coroded in the tips (could not visually with it installed).

 

Unfortunately the choke light never comes on, engine running or not, key in all position, I checked and the bulb is good. Any suggestions?

 

when you car is running you should read 13.9-14.6volts
when its off you should read 11.30-12.6volts. in rare case it will be higher or lower, i think its you alternator. check the wiing to the alternator, the alternator might be fine, just the wiring is shot.

 

Then use your meter to test the output voltage directly at the alternator output stud and case ground, with the engine running, of course. If it doesn't agree with the dash instrument, you have a wiring/connection problem somewhere. Don't overlook the mounting bolts for the alternator, since the grounding for the alternator is through its mounting.