charging issue

[wheeeedr1]

need help,i have done and checked everything i think, this started when i put a 350 in it, was a v6 car, i am running a v8 alternator, here is my problem, when i start my car cold all is good but i start driving it and about 6 blocks down the road my alternator quits charging, i have a brand new battery, and alternator, i know it is not my gauge, i have checked the alternator and it is not putting out 14v, my wiring is as follows, from my bat post on alternator to starter solenoid, (put in a ford remote starter solenoid to keep out of heat, from here battery cable goes to the battery, one wire runs back to the alternator to the plug in and the other runs to a fuse i believe on the firewall on the other side of the fuse is a wire that runs to the plug in to the fuse box, i have ohmed it out and resistance is normal, this is the 2nd alternator i have put in it. i have run a ground wire from the alternator to the battery and this did not help. the next day this will all start again. all wiring looks correct to me, could really use some help i can't find my problem.

[cjbiagi]

Is this a one wire alternator or a traditional one with 3 wires?

[monzabill]

and did you replace harness the V8 from monza?

[wheeeedr1]

traditional 3 wire, no did not replace harness

[cjbiagi]

What voltage are you getting out of the alternator? may have to wait for Spencer, I am sure he will shed some light. I assume you checked the belt tension?

[wheeeedr1]

getting about 14.2 when i start it but when i lose charging it just shows battery voltage, did check the belt tension. need to correct something, the wires running from the starter solenoid one goes back to the alternator plug, one runs into the firewall, not the fuse i originally said it went to and of course the one goes back to the battery. my fuseable link on the positive battery cable is the one that runs to that fuse on the firewall. thanks for the help so far

[monzabill]

im thinking somethings wired wrong in dash guages or just a light? i have seen this with idiot lights before

[monzabill]

if its a light does the charging lamp light up when cranking?

[cjbiagi]

You may have a resistance issue within the harness or at the connectors. If it is charging normally when cold and drops off when it gets hot I would check all your connections for corrosion or poor joint connections. Assuming it's wired correctly since it charges normally at first. How are all your grounds, specifically the engine ground and chassis ground? Since this was a swap you may have left off some grounding wires or straps....just thinking out loud. I ran a heavy braided cable from the engine to the chassis to make sure I have a good chassis ground.

[zeke]

Check your light circuit. Small tan wire at the two pin alternator plug. With it unplugged from the alt. ground it, with the key on, the bulb should light up brite.

Check the sense circuit - Measure the voltage on the other pin with the large red wire, should be same as battery voltage.

Check the alternator output wire terminal and make sure it runs to battery positive on your solenoid.

Check belt tension, should not be able to turn alt fan with your thumb.

Load test battery, some auto part supply places do it for free.

[spencerforhire]

Everything Chris just said. lol
Plus check all ground wires; Battery to block, battery to body and make sure the alternator is bolted TIGHTLY to it's brackets and the brackets tightly to the motor.
You also state that you've tried two alternators; was the symptom exactly the same with both? Were they new or used? Are you driving around with a multimeter in the car or are you looking at the OEM gauge?
If you put the meter right on the alternator does it read any different than if it's at the battery? If you start it and just let it idle, does the voltage slowly drop from 14.2 to 12.5? Or does it cut out quickly only if you're driving?

[firebird77clone]

It's the alternator. Did you keep the receipt?

[wheeeedr1]

same thing has happened with both alternators, yes i am reading the voltage with a multimeter off the alternator, i am using the ground strap that was in the car, goes from firewall to block, also have checked grounds, even ran a ground from alternator to battery, only thing i could think it would be maybe is to small of wiring run from alternator to solenoid, it is a 10 gauge, do i need bigger?

[wheeeedr1]

both alternators were new, also my circuit has a factory gauge not lite. alternator that i put in is a 62 amp

[zeke]

The alternator still needs to be excited (turned on) with the small gauge wire on the 2 pin plug. Check for switched 12volts then.

Charge or output wire should be at least #8 wire or two #10's. If you are not using the factory charge wire, your amp gauge won't read right.

Should be a 10 or 8 gauge wire from battery negative to the body as well as the large #2 to the block.

Edit: Don't rem if they had ammeters or voltmeters. lol