help tracking down voltage drop @ idle

[donkey_punch]

when i'm idling, say at a light, i get a voltage drop after about 10-15 seconds of idling. the problems begin after i idle for some time cause the volts keep dropping. so if i get stuck in a crawling traffic jam i'm ****ed my battery will drain. cause i have to almost rev to 1800 rpms before it charges. with the exhaust i have i can't keep reving it, it's way too loud plus annoying to sit there and keep reving just to keep the battery charged.
also once the volts get low the car will stall if i don't rev it.
so my first thought was the alternator. which is a powermaster one wire(i beleive 200 amp) not even 2 years old with not even 4000 driving miles on it. my mechanic friend suggested it was the regulator or diodes inside, and he knew of a place to get it tested and fixed. i got a call today, the alt. is perfectly fine it passed all the tests and i even found out that it starts to charge @450rpms.

so i asked my friend if it could be the U/D pullies and or the fact that i put the original pulley back onto the alt. but the rest are u/d. he didn't think so. he was suggesting that it could be the battery light on the dash that is suppose to trigger the alt. ( this is what i gather from our conversation)

anyone here have any suggestions.

Thanks
Joe

 

[Fopar]

battery light on the dash that triggers the alt?... uhhh no.

It's your underdrive crank pulley, live with it....

 

[Stanger007]

I'd double check the engine grounds to make sure they are tight and not corroded.

 

[badstang123]

I have similar issues. I'd say it's the underdrive pulleys too.
- Justin

 

[Blackened302]

curious... do you have a tune to run w/ your cam?

reason i ask: thought my electrical system was crapping out on me (don't have underdrive pulleys installed yet), but when i finally did some real tuning, the symptoms went away.

just throwing it out there...

 

[HISSIN50]

Your friend was right about the switch circuit but wrong for your application I think. The switch circuit is what excites the alt in stock form. The I terminal sees 12 volts come from the ignition switch (via the battery light and a 500 ohm resistor in parallel) and knows you wanna go. When the alt functions properly and excites, the I terminal becomes ungrounded and the light goes off. When the alt is not charging properly (like when you turn the key on but dont start the car), the I terminal remains grounded, which makes your idiot light stay on. Cool?

Now if you have a true one-wire alt (just a charge cable, and the alternator is self exciting, where you need to rev it to some given engine RPM [like 1500 engine RPM] for it to start charging), you dont even use the switch circuit anymore. It's moot.

If you did reuse this circuit (it's an option, and a wise one at that, on many one wire alternators), then we can diagnose the circuit further.

It sounds like your one wire alt (if a true one wire) is not staying excited. Place a little blue pill on top of the alternator..........

Seriously, when it was tested, was this a bench test? Did they just use a charge cable or did they hook up regulator plug to the alt as well? If the latter, they did something that isn't done on your car, which could account for the difference (and give us a direction to go).

With one wire alts, it's super important that the charge cable is in awesome shape. For your 200 amp alt, you should have 0 or 2 AWG cable (2 is insufficient, but kinda popular). Ensure the cable connections are tight and clean and that the in-line fuse connection is in good shape too. Also check the PDC connection. See if the cable feels exceptionally hot (be careful and all) when the alt starts acting up (you can turn the car off to test this - we're looking for for a resistive cable, which makes heat. The cable will seem hotter than it should be).

Random thoughts.
Good luck.

 

[donkey_punch]

i've been thinking about swapping the stock pullies on just to rule the U/D pullies out. we'll see how things go today.

Paul - no tune, i've had that cam for almost three years now, never had a problem like this before. it's nothing crazy, very mild Crane 2031 cam, kind of wish i went bigger.

Hissin - funny you mentioned about the gauge of the wire. the wire that was provided with the alt. i think is like an 8 gauge. i've been wanting to up the gauge of the that wire and the main battery + wire for some time now.
also it's advertised as a one wire alt but in the instructions they had me tap into one of the three wires that is on the original alt harness that is then connected to a small terminal on the alt. i wish i could find the instructions now. dammit

excuse my stupidness but whats PDC connection?

and thanks for everyone's suggestions, usually i get no where with my tech questions.

Thanks
Joe

 

[HISSIN50]

i've been thinking about swapping the stock pullies on just to rule the U/D pullies out. we'll see how things go today.

Paul - no tune, i've had that cam for almost three years now, never had a problem like this before. it's nothing crazy, very mild Crane 2031 cam, kind of wish i went bigger.

Hissin - funny you mentioned about the gauge of the wire. the wire that was provided with the alt. i think is like an 8 gauge. i've been wanting to up the gauge of the that wire and the main battery + wire for some time now.
also it's advertised as a one wire alt but in the instructions they had me tap into one of the three wires that is on the original alt harness that is then connected to a small terminal on the alt. i wish i could find the instructions now. dammit

excuse my stupidness but whats PDC connection?

and thanks for everyone's suggestions, usually i get no where with my tech questions.

Thanks
Joe

Joe, 8 gauge wire is rated for about 50 amps. Our stock wire is 6 gauge as I recall, and we only have a 130 amp alt stock. Redo that cable (don't run both in parallel - that's a fire hazard). 1/0 is the only thing rated for 200 amps. That said, if you use 2 AWG and simply fuse the circuit for the rating of the weak link (your cable), that should work ok.

The PDC is the bolt connection on the side of the underhood fusebox where the alternator cable and battery cable join. That connection is arguably the most important on the car and it corrodes.

If you can look at the color of the wire (the one on the car) you tapped into, that might shed some light. If it was lt grn/red, that's the switch circuit. If you use this feature on your alternator and the circuit failed, the alt would not turn on.

Good luck.

 

[MisterCMK]

The wire size depends on the current load as well as the distance. A #8 would be fine if you are only going a couple of inches where as you wouldn't want to use it to go from the front to the back of the car. (Just an example)

 

[final5-0]

I would like to share some findings after a lot of data gathering
on how our Stangs deal with batt voltage during many different
kinds of driving conditions

I can't find the data at this time
but
let me give you what I can remember

I will say I got ALL ud pulleys in place on my little GT
and
I run an idle speed of about 850 to 900 rpm

Also ... I run no big sound system ... just the OEM Mach 460

I never saw the batt volts dip as you describe

At night I do see the head lights dim just a tiny amount
but
I can add like just 100 rpm and they go to full brightness

Joe ... sounds like you got more going on than what pulleys would cause

Grady

 

[HISSIN50]

The wire size depends on the current load as well as the distance. A #8 would be fine if you are only going a couple of inches where as you wouldn't want to use it to go from the front to the back of the car. (Just an example)

Let us know how that works out for ya. I dont see how 8 AWG (in any length) would handle continuous 200 amps. Post pics after the fire.

Just messin man. I'd never post anything remotely close to suggesting that 8 AWG is capable of this task - posts can be misinterpreted (and that was my point here). Some newb might think 8 AWG is ok for 200 amps.

 

[donkey_punch]

well it is tapped into the green wire with red stripe from the original harness. i even put in a new tap with a new wire to the alt, just to rule out the other wire and connections.
the place i went to today, of course didn't have 2 awg so i got 1 awg wire.
so now i have this monster of a wire, the 1 gauge from the alt to the battery.
i couldn't change the PDC wire to a 4 gauge like i wanted to. i put in an aftermarket battery clamp View attachment 366406 but the 1 gauge alt wire took the 1 gauge spot and the starter wire took the 4 gauge spot. so i had to keep the PDC wire and use it in one of the two 8 gauge holes.
i was thinking of taking two 8 gauge and putting them in the 2 slot left on the clamp and then connecting them together to a 4 gauge wire and then the 4 gauge to the PDC? anyone have any thoughts on this. my original alt wire split into 2 smaller gauge wires that were then connected to the same ring terminal on the PDC.

so i go take here for a spin and man did she start right up. it was like i didn't even have to crank it. i barely turned the key and it started. but now she doesn't want to idle. but it doesn't seem to be from a voltage drop. the volts drop as the car is stalling not the other way around like before. i wish i had time to mess with the idle but it's late.
so i won't say i fixed the probelm as i'm not sure. the car won't idle long enough to see the any voltage drop except while it's stalling. but i did notice a big difference just starting it.
one thing i did notice today, was if i put the key in the ON postion i don't see the battery light. could this be the root to my problem?
hopefully tomorrow i will have some pic

thanks
joe

 

[donkey_punch]

i forgot the most important thing. the son of a bitch started to throw the check engine light.
all the parts store around here look at me like i landed from another planet when i ask them to pull codes on a car with OBD1. so i have to get that done also.

 

[HISSIN50]

Hey Joe, that's about how my projects go.

Let's see. I got kinda lost on the cable thing but I'm glad you upgraded (please ensure you get a fuse on the cable as well, if you don't already).

When I've looked at stereo battery cables, I've run into similar logistics quandries. I have a distribution block that I'm going to end up using instead (they work well for simply giving you extra ports to work with in a situation like yours).

I am thinking that you could put the starter cable on the PDC lug if you wanted too. I dont see why that wont work. Then that port is freed up.

I'm thinking that there could be an adaptive issue going on and/or something got knocked loose while you've been working on this. Once you get the code we can figure it out. You might not be good lookin enough to get codes pulled. Parts stores never have for me, yet a female family member (also with an OBD-I EEC-IV vehicle) can get her codes read at the part store. I'd just use the paperclip method or get one of the LCD-display readers from CSK.

Not seeing the battery light could be a real issue. However if that was the case, I am not sure if your alt would even charge. I have once seen a regulator burn in such a way that the reg never grounded that circuit (the light never came on) but the alt worked fine. I dont know about the differences in one-wire alts vs a conventional alt to say anything more informative.

 

[badstang123]

I'm wouldn't even begin to make the claim that your issues is related to this, but I would also upgrade your ground wires as well. In a cars electrical system the ground cable is near as important as the power. I put a link below to what I did. Again I'm not saying in any way that this is your problem, but I would recommend it to reduce resistance within your electrical system. And get your pulley's switched just to isolate where the issue could be. I'm just giving you my recommendations from a lot of playing with wiring and electrical issues I've had with my car. Good luck

http://www.cardomain.com/ride/2327549/3

 

[donkey_punch]

as you can see in the first pic the balck wire was the original wire on the car before i did the one wire alt. and you can see the end that was split down with smaller gauage wire, but still connected to the same ring terminal.
you can also notice the bull**** wire (red one) that was suppied with the higher output alt. it's smaller than the original.

the second one speaks for itself. it just shows the new clamp with the wires installed

badstang123 - 2 years ago i put a 1gauge ground wire from the battery right to the frame rail under the battery. i also put a new one from the motor mount to something else ( i forgot where it went). but i used this flat braided wire that's about 1 1/2 inch wide. Saturday i'm going over those connection to make sure there isn't any corrosion. i still want to route a 1 gauge ground wire to where the original ground wire goes, but thats another project. btw nice system

Hissin - i bought a 200 amp fuse with a holder to go inline on the alt wire, but i didn't put it in yet. of course the day i need to use my wire stripper and crimper i cou;dn't find them. even though they have been in my face for the last 12 years yesterday they walked of on their own. so i had to cut the 1 gauge with a razor blade . i also have to find a place fo this monster fuse, and since the holder is plastic i don't want it sitting on the enigine itself. so i'll have to find a way to mount it on the inside fender, but still keeping the length of the wire as short as possible. as you can tell in the pics i don't have much room to work with.
as for connecting the starter wire to the pdc, i thought of it. but once i upgrade the wire jumper wire from the PDC i lose that wide, long , flat terminal. and then having two 4 gauge wires with ring terminal on top of each other. i won't be able to put the PDC cover back on.
Also do you think i should put a fuse on the 4 gauge going from the battery to the PDC?

thanks again for all the help guys
Joe

 

[HISSIN50]

Joe, the OEM cable splits into two fusible links. That's the OEM circuit protection. It's normal.

You're a better man than I am - I actually use a razor blade and a set of dykes to strip huge cable. My cutters wont accept those huge cables.

I personally see no need for a fuse between the battery and PDC. Others may feel different (there isn't one OEM so I dont see why we need one).

Justin, what do you think about his lack of hook ups? Is there a power distribution block you know of that could help him? How about using a couple of them? Or can the holes be drilled out to accept larger cables? I use real cheap blocks (5 bucks each) so I am not well versed in the nice stuff that is available.

One solution I have used, though not pretty, is to use a power distribution stud. It's just a stud that you can connect a bunch of terminals too. You insulate it and then mount it where you want. Some cars have them OEM (like 4th gen Camaros, right behind the battery).

Good luck Joe.

 

[donkey_punch]

well i just took the car to the family mechanic, he was able to pull codes for OBD1. my CEL turned out to be my O2s being bad. i thought it was running pig rich cause i have no cats
i don't have that serious voltage drop anymore, the volt needle pretty much stay on R in NORMAL. just have to play with the idle alittle, i bumped it up to 1000rpms, cause while they were trying to pull codes in the running test it would keep stalling. and i told the tech if it starts getting quiet she's going to stall you have to rev it alittle. he was too busy looking at the scanner, he caught it a few times. but i made it easier for him, just to bump it up.

Hissin - i was thinking, while waiting at the mechanic shop about hooking up the starter wire and the jumper at the PDC. i have an extra ring terminal for a 1 gauge wire. i'm going to try and see if i can put both starter wire and PDC jumper in one ring terminal. i was think sodering it all together and then crimping it? it might work out.

but i still don't get the battery light when i put the key in the ON position. any thoughts on that?

 

[HISSIN50]

I'll let the other guys comment on having two cables in one terminal. I try not to do that kind of thing because it's hard to marry the strands so you have good connectivity with the terminal with respect to an air-tight connection.

Just to rehash the alternator light: If you have your I terminal (the green and red wire) connected to your new alternator, ensure it shows voltage when the key is turned on. If not, we have to trace that wire (or I have a quick work-around for you for diagnostics. You'll need to spend a buck at Radio shack though). If you have this, the battery light circuit should be functional. But like I said, I *once* ran across an alt where the regulator never grounded the I (switching) circuit. The alt worked fine. You just had to watch the voltmeter.

Also, because of all of this, I'd install your DMM in the car (or get a cheap voltmeter gauge and set it somewhere in the car) so you can keep tabs on things.

The stock gauge is no where near accurate enough to interpolate for purposes here (I.e. there's a huge difference between 12.0 volts and 12.6 volts). The stock gauges have a lot of hystersis built into them (new car owners find gauges that twitch a lot to be disconcerting so they take the car to the dealer unnecessarily).

Also, when you choose your power source (for the DMM), measure the voltage at that location and compare it to battery voltage (at the battery). You will probably read 1/4-1/2 volt higher at the battery. Knowing the amount of voltage drop you have allows you to take that into consideration. You can get DMM's on sale at Harbor Freigt for under 5 bucks. They work just fine.

 

[donkey_punch]

well after picking up the car then going back to work the car work fine as i stated above. but on my ride from work to home it start to do the same **** again. so at this point i'm lost as to where to go from here. at one stop light it will idle steady no votage drop, at the next it will idle for 6-7 seconds then jump up alittle and on the way back down never recover and stall. at the next light idle for a while jump up recover jumps again but then never recovers and stalls. then at the next stop it wants to stall as soon as i come to a stop.

Hissin - i hope i don't confuse you but here i go. that wire tap into the green and red wire goes to a connection on the alt. but there are two connection to choose from they are right next to each other. i have been using the one on the far outside cause this is the one the instruction said to connect the tap too.
but i put the wire tap on the other one today, just to try it out. even thought while driving, the car wanted to stall more when coming to a stop. the volts would drop more than before while it idle for the short time that it did. the battery light would come on after it stalled and if i put the key in the on position. i also tested the green/red wire for volts while the tap wire was on this connection, with the key in the ON position. it read .633v
i put the tap wire to the far outside connection and the green/red wire read 12.13v
i'm wondering if this helps in any way.
cause at this point i ready to put the stock pulleys back on. if that doean't help i'm buying a stock replacement alt. if that doesn't do it i'm stripping it and making it dissappear

ahhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh