200 amp alternator not what i had expected...

davesexplorer · December 21, 2004

superedge88 said:
davesexplorer said:

how does the battery make a difference since batt = 12v and alt = 13.5-14v

you are not getting any power from the battery unless you are overdrawing the alternator... a new battery will not solve your alternator problem...
=QUOTE]

He is overdrawing the alt at idle, that is why his old battery is probably dying since I assume it has been deep cycled too many times and is not charging to it's fullest capacity. Obviously it is hard to diagnose without actually checking out the vehicle, but I would definitely suspect that the battery is on it's last legs because of weak output of the alt at idle.

Click to expand...

yes all correct but why buy a new battery, which wont help the dimming much at all, and have it fail because of constant discharging...

The problem therefore lies in the alternator or its wiring, the dimming you see comes from all your accessories running at ~14v from the alternator, when you overdraw the alternator your accessories must then run off the battery, 12v that 2 volt difference is what makes your lights dim, your accessories are taking power away from your lights, and taking power from the batt.

So everything you said is right, but you didn't address where the problem lies, the alternator system...

davesexplorer · December 21, 2004

Fish Man said:
i really dont want to live with the dimming...i mean i know that yes with all the stuff running i should get some dimming and thats fine. what bothers me is that with nothing running i get alot of dimming. thats not cool at all. the battery gauge dances around more than it ever did with that crappy old 95 amp. i think ill get the battery checked out and see what that alt is putting out at idle. dunno the specs on the alternator. dunno if the belt is slipping...i would think id hear that though? would be something to look at. so dave are you saying that a new battery wont help? i'll have to try some bigger wire...

yea definitely check the alternator, could be something wrong with it too?

The battery will only help when your voltage drops to its voltage range, the battery cannot supply above its charged voltage state, if its 12.9v resting, It cannot supply your components @ 14v. Bigger batt will help if your voltage is dropping below the batts resting voltage though..

Fish Man · December 21, 2004

ill get the alt checked out...dunno if something could be wrong with it but i woudl think it should be doing better than it is now. i just dont see how this thing would not be able to power my stock head lights. thats pretty rediculous to me...

davesexplorer · December 21, 2004

I agree with you, if it cant power the stock headlights.. tsk tsk...

97BlackX5.0 · December 22, 2004

okay... im having the same problem with my stock alternator at idle running my headlights (silverstars) my heater and the rear heater full blast with the fogs on and having a 200watt amp hooked up but not pounding.... in my opinion its almost always the battery....do this for me.... somplace that you have a vehicle to jump your car or a battery charger... turn all your crap on without the car running.... leave it run for maybe say 10 minutes at the max.... then turn it off.... and immediately try to start your truck... if it wont or its really really slow then its your battery.... it has lost the resiliency that it once had.... it will still hold a charge and start your truck but the power out put is way down and isnt much good other than just starting the truck.... this happens alot to older batterys.... no matter how big they are this can still happen to.... im also assuming that you have a maintenance free battery.... if you can open the indivdiual cells you might want to get a cell tester..... try it again but instead of starting the truck after using the battery for ten minutes ... test the cells.... ill bet you have at least one or two bad....

i had this exact problem and i replaced the battery and bingo it was gone.... i kept the old one around to jumpstart lawntractors and stuff like that cause it still works for that... just cant put a load for any lenth of time on it or its kaput...and needs to be charged by a battery charger....

superedge88 · December 22, 2004

davesexplorer said:
yea definitely check the alternator, could be something wrong with it too?

The battery will only help when your voltage drops to its voltage range, the battery cannot supply above its charged voltage state, if its 12.9v resting, It cannot supply your components @ 14v. Bigger batt will help if your voltage is dropping below the batts resting voltage though..

That's my point, he should get a hybrid battery that can take large discharges if he is going to stick with this alternator. I suspect that his current battery has already been damaged by this alternator, I am assuming it is a normal starting battery. I realize getting a new battery will not fix the problem, but with a hybrid battery it will be able to handle deep cycling caused when the car is at idle sucking juice from the battery, instead of a normal starting battery being killed by this deep cycling. This will not help much with the dimming, only on a small scale.

CDW6212R · December 23, 2004

Has any basic check been done on the alternator, or battery? First, check the voltage with the engine cold and off, before starting it. Second, check the voltage while running, without loads, and then with loads.

Under normal usage, the cold battery voltage should be over 12 volts, and actually more than 12.5 volts. The charging voltage should be in a range of about 13.5 to 14.5 volts. If not, then one of them is bad.

If those basic tests pass, then remove the alternator, and ask a generator shop how many amps it makes at idle, etc.

I just bought a 160 amp alternator for my 99 Limited mail vehicle. It is supposed to make 85-95 amps at idle. That will be plenty for me.

I suspect that the alternator is not making enough power at idle. "Explative" the battery, take it out with the vehicle running. Unless the battery is dead, or noticeably bad, it will have no affect on the running of the truck.
Good luck,
DW

Makahveli · December 25, 2004

I had the same problem, yellow top, and 200 AMP alternator with new cables. What fix the problem was when I removed the negative cable from the frame and sanded it down to a smooth shiny surface, after doing that it was like a brand new truck. still little dimming when bumpin cause my amp is 2400watts, a capasitor can help but I don't believe will elimanate the problem.

Mbrooks420 · December 25, 2004

I would guess that Terdrocket has the best answer. I was going to upgrade to a larger alt. and my mechanic said not to even bother if I wasn't having a lot of problems with the stocker. e said all the high wattage alternators he had seen were piss poor at low rpms, and often would thow a check guage light while sitting at idle because it couldn't keep the voltage where it belonged at 1,000 rpms. I looked on the internet and found other people complaining of the same thing. You may need a battery, but I would guess that the 200 wat alt sucks at low rpms.

jordan23 · December 26, 2004

Makahbeli has it on the head...upgrade your alt to ground wire with 0 or 2 guage and sand down the ground location WELL! I had major dimming in my truck until I upgraded ALL grounds to larger wire than my amp required...you can't go wrong with 0 guage!!

Also, I have heard many instances of high amp alternators not performing at idle speed...they need at least 1500 rpms to perform properly.

Good Luck!

Jordan23

Makahveli · December 26, 2004

so if your one of those peeps with the BBK throttle body, is there a way to adjust it to idle at 1500 RPM? And would it be fine from there?

Makahveli · December 26, 2004

By the way my ex is manual, I know that it can be a problem with automatics

taxx · December 27, 2004

davesexplorer said:
yes all correct but why buy a new battery, which wont help the dimming much at all, and have it fail because of constant discharging...

The problem therefore lies in the alternator or its wiring, the dimming you see comes from all your accessories running at ~14v from the alternator, when you overdraw the alternator your accessories must then run off the battery, 12v that 2 volt difference is what makes your lights dim, your accessories are taking power away from your lights, and taking power from the batt.

So everything you said is right, but you didn't address where the problem lies, the alternator system...

NO! A dual purpose battery like said by a couple of us will help. It can be cycled without ruining it. And a battery puts out the 14v not 12. Thats not the difference that causes the dimming. True the problem is the alternator not putting out much juice at idle, but a dual purpose battery will keep up much better than that stock battery and can handle the cycling. It won't help completely, but will make a big difference. Unless you spend a fortune on one that puts out alot at idle thats the best alternative. Honestly I don't know if I would want one that puts out a ton of juice at idle, thats going to be harder on the battery than anything else as much as I idle my vehicles.

There is no one answer for this problem, as you can see from all the responses. You need to do some research and decide how you want it to act. If it was me I would put a better battery in (dual purpose) and let it go. I know a lot of people with that setup, it still dims a bit but the batteries last a long time and everything seems to work well. There are always going to be trade offs. The perfect setup is going to require you to put a good amount of time and money in the power system.

Nasty350LT1 · December 27, 2004

Go for an Optima Yellow Top

Fish Man said:
taxxman-thanks for the info. maybe i should upgrade my battery? i really dont care about running all my crap at idle...but i would think that i should be able to stop at a stop light without my headlight dimming. thats just rediculous. so this recovery time thing...if i run it for awhile technically that would bring the battery up to normal right? i drove it for 5 or 10 miles today, stop and go...how much does it take to get it back up? since its so cold ive had the heat way up and even the friggen heater fan slows way down when i stop at a light. and now its been doing this rediculous shudder thing at lights too. kinda pissed about this...wish you could give me a magic answer!

I put the same alternator in my 99 X and put a 4 gauge wire from the alternator to my OPTIMA YELLOW TOP battery. I then put a 5 Farad Block of Capacitors before my MTX 81000, which is driving my 3 Infinity 12" Subs connected at 2.7 OHMs in a custom box. My lights never dim at idle or in DRIVE with my foot on the brake with everything running "HARD & NASTY" with the A/C on , Highbeams on, rear defroster on, wipers on High, in stop & go traffic. My voltage never drops below 13.7 volts... :exp:

davesexplorer · December 28, 2004

taxxman2k said:
NO! A dual purpose battery like said by a couple of us will help. It can be cycled without ruining it. And a battery puts out the 14v not 12. Thats not the difference that causes the dimming. True the problem is the alternator not putting out much juice at idle, but a dual purpose battery will keep up much better than that stock battery and can handle the cycling. It won't help completely, but will make a big difference. Unless you spend a fortune on one that puts out alot at idle thats the best alternative. Honestly I don't know if I would want one that puts out a ton of juice at idle, thats going to be harder on the battery than anything else as much as I idle my vehicles.

youre telling me a 12v battery will put out 14v

CDW6212R · December 28, 2004

The Alternator will make 13.5 volts or so, less under a full load, and more if the battery is low and there is nothing else on. Night,
Don

hunterdan · December 29, 2004

CDW6212R said:
I suspect that the alternator is not making enough power at idle. "Explative" the battery, take it out with the vehicle running. Unless the battery is dead, or noticeably bad, it will have no affect on the running of the truck.
Good luck,
DW

I can not stress how much this is a bad idea. Alternators are regulated by the battery and the loads. If you remove that battery, the alternator can and will send a huge spike of several hundred volts through the system. Yes, the alternator should run everything, but it still keeps an eye on the battery to keep it charged. If that battery suddenly disappears, it sends massive amounts of power to recharge a battery that isnt there. Just take the car to autozone or advance or a place like that and have them test the battery and the alternator. Not the most accurate tests, but if the guy knows what hes doing, it can be accurate. When I hear of people saying, just pull the cable off the battery, I cringe because it can lead to some serious damage and very expensive repairs. These arent the older externally regulated alternators of the past, these are some highend very complex units. I might be wrong how the regulator works, but still removing the main power source from a vehicle is bad.

Dan

taxx · December 29, 2004

davesexplorer said:
youre telling me a 12v battery will put out 14v

Yup. any good 12v car battery puts out more like 13 - 14 volts. Thats why there are voltage regulators.

CDW6212R · December 29, 2004

Dan, I hope you read the whole thread. If you did, you might have seen that my comment was in context of the suggestions by others. No one had yet suggested making sure that the basic conditions of the battery and alternator were good. Every suggestion was a guess based on no basic evidence. My comment was simply that the battery was not the problem. If the battery is not sucking more power than the alternator can make, then the alternator can power the battery and everything else fine.

12V batteries do not "put out" 13-14 volts, ever. At full charge they will be in the high 12V range. As I did mention, alternators put out about 13.5 to 14.5 volts, all of the time.
Regards,
DonW

davesexplorer · December 29, 2004

CDW6212R said:
Dan, I hope you read the whole thread. If you did, you might have seen that my comment was in context of the suggestions by others. No one had yet suggested making sure that the basic conditions of the battery and alternator were good. Every suggestion was a guess based on no basic evidence. My comment was simply that the battery was not the problem. If the battery is not sucking more power than the alternator can make, then the alternator can power the battery and everything else fine.

12V batteries do not "put out" 13-14 volts, ever. At full charge they will be in the high 12V range. As I did mention, alternators put out about 13.5 to 14.5 volts, all of the time.
Regards,
DonW

Ahh someone agree's with common sense.

200 amp alternator not what i had expected...

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