Voltage Drop?

[grayt]

Driving home last night and got into the long skinny pedal and noticed at first the headlights got real bright(because of the volt blaster i imagine) but then the went dim and the motor kind of bucked. I tried it again and flipped the scanmaster to volts and watched it and after about 2-3seconds of 14-15 volts it dropped to 11.5-11.8 then bucked. Is my alternator punched or is it the internal regulator taking over?

 

[garyk1970]

check you battery terminals,make sure they are clean/tight.check alt output post and check for the same.check ground from batt neg to block,batt neg to fender,pos batt to starter.if all is good,have alt checked,dont forget to test alt hot and cold.then load test batt.if all else fails,disconect volt booster and see if its culprit.test these first and let us know the results.

 

[my1stgn]

Holy crap the same thing is happening to my GTP, I was going to lunch then all of a sudden the car was wanting to die and the dummy lights came on prematuraly like when you have the key in position two and the engine off, except the engine was running. 99% of the time its either the alternator or the volt regulator (if you could get it seperate)....... but not with my luck. I bought a new alt. and threw it in about half an hour ago. Volts are still @ 11.5-11.8 and when I unplug the volt. reg. they drop to 10.5-10.8. I would have thought it would have jumped to 14-14.5 with it unplugged
Oh well, I guess Ill do some further diag tomorrow. Voltage from Batt. Negative to chassis ground is only .05v and alt voltage and voltage at terminals is the same so there really isnt any type of voltage drop accross the cables........

 

[garyk1970]

my1stgn, start car and then unhook pos battery term and see if voltage goes up- i had a car last week that a bad cell in battery was pulling the voltage down.

 

[mikestertwo]

I still haven't figured out why guys run volt boosters unless they like eating alternators, ruining batteries, robbing horsepower, and causing a host of other electrical problems. If your fuel pump can't deliver enough fuel at 13.8 volts, get a bigger pump. The stock ignition puts cars in the 9's on 13.8 volts. It takes horsepower to raise that voltage above where it belongs.

 

[my1stgn]

my1stgn, start car and then unhook pos battery term and see if voltage goes up- i had a car last week that a bad cell in battery was pulling the voltage down.

Thats what I was thinking too (after talking to a few buddies of mine at work) Im going to put a new Optima battery in there tonight, my friend will be bringing it by and its free so fvck it. I was going to take the battery out the GN and put it in the GP but since Ill be getting a new battery for it, ill just swap them out tonight. Ive heard about pulling the battery post before (old school method I used to do as did everyone else to check the alt.) but with all these dam computers in the cars I dont want to cause a voltage spike and fry another PCM. Ill just replace the battery for now and if that dont fix it, Ill have to really diagnose the car!

 

[my1stgn]

Well there goes that. Installed new battery with 12.25v (uninstalled) then once I installed it, I started the car up....... to see the voltage drop from 12.1......12.0.....11.8.......11.6........11.3.....11.0.......10.8......10.5......10.3.......10.8.......11.2.....10.8......... So now I have to actuall diagnoses the problem. Somthing somewhere is causing a lot of current draw and I will start isolating things..... tomorrow, Im tired today!

 

[garyk1970]

still sounds like alt,ive bought bad ones right off the shelf....dont forget to check alt HOT & COLD.diodes going bad in alt will have the same symtoms (bad electronics will do better cold)that you describe too.when diodes go bad,it will short out alt and pull alot of power.have it tested by a tester that covers all the bases.if you had a drain/short/pull in car,most likely it will be a consistant pull.keep us posted.

 

[zeus87gn]

I was going to say battery too, but that has been eliminated.

I will vote for rectifier going south in the regulator. If you have an automotive electrical shop nearby they can let you know for sure, and probably install better quality parts at that. I have seen bad alternators off the shelf as well. I won't trust Auto Zoo alternators anymore, had too many of them go bad too soon for my liking.

 

[Sinister CO]

Have you checked the trigger wire that plugs into the alternator? With the key on, that wire should be hot. If you don't have power there, the alternator won't charge.

 

[my1stgn]

I havent checked power going to the field in the alternator yet, but I find it hard to believe my alt took a crap, then I replaced it with a bad alt. and got the same results. Dont get me wrong, this is believable and possible, but I just think thats weird........Ill do some further tests tonight and let you guys know!