Recently, my car's charging system can't seem to keep up with the load. When first started it seems normal going to between 13.5 and 14 volts. However after driving a while it will drop to about 13.2-13.4, which is also normal. However, when i start adding load it just can't keep up anymore. If i run my headlights, A/C fan on high, cooling fans running, etc, the voltage will drop below 12 volts when stopped at a light, and will only get to 12.0-12.3 when the rpms are up above 1600. Then if i shed load (drop the A/C & headlights for instance) the voltage doesn't seem to climb back up.....it might get to 12.2 at idle and 12.5 at rpm. So something is wrong. I had the Alt check out and it was putting out 108 amps (on the bench...cold), and checked out normal. I replaced my battery....no help. Cleaned all my grounds (at least those that i know of)...also no help. So now i'm thinking that my Alt gets weak when put under a load and heats up *** OR *** i need more than 100 amp capacity. I'm thinking of getting a new alternator and considering a 140 amp (same price as the 100). Is there any downside to getting an oversized alternator? Has anyone else had this problem & and how did you repair? Has anyone else gone to a 140 Alt????

 

you could also benefit by changing out to 2 or 4 ga cables this will help as well besides if you do the bigger alt you must do this otherwise the wire will get fried due to the extra amperage!! havent done this to my vette yet but have on my jeep and yes the wire got fried

 

Ralph,

The large red wire that comes off of the alternator goes back to a 12 guage fusible link behind the battery inside of some of that black wiring harness covering stuff. It might be worth checking out if the fusible link is partially burned through.

 

thanks guys.....does anyone think i need a 140 amp unit? Is anyone having simialr issues with the 100 amp unit.

I'm guessing that the 100 amp unit is enough as adding the individual loads gets no where near 100 amps. If that's the case, mine must just be getting weak as it is just not able to maintain voltage under load......however if there's no down side to a 140 amp unit (other than beefing up the main wire back to the battery), why not go oversized?

 

I don't see much of a downside to it, but I still think your current one SHOULD be able to handle the loads you're putting on it. I've noticed my alt gets affectet by ambient heat bigtime. On 90* days running down the highway mine drops to 13.4v. After sitting for a while or if the temps drop back into the 80s its back up to 13.8-14.0.

 

I threw a 140 in my 90. nothing really changed here. I did it as a rebuid option. I also rebuilt the grounds and positives.

my voltage gauge blips when I put the turn signals on so I thought about doing this. didnt fix it.

BTW, I have no idea what the actual readout is since the 90s gauges suck.

 

I got tired of failing alternators and bought a GM Kool-Charger
(Model #: 7935S.) from Tuff Stuff. http://www.tuffstuffperformance.com/

No problems so far, idle is around 14.2 while driving stays at around 13.7.

 

Ralph,

I used to have a 140 amp on my car. I ran it for about 3 months before ripping the one whole side of the case off it! It wasn't the alternators fault, but rather the lack of the one alternator brace. I was caught without a replacement so I opted for the lesser one, stock, so I could race that day. Haven't gone back and doubt I will. As now I have no charging issues and can't see spending the extra money for one.

Sounds to me like you need one though. I would not get it from a local NAPA or AutoZone though. I would order it through Jegs or Summit and get a good quality one. I know what your going to be doing with you electric water pump and fans so you will be taxing that alternator at each event pretty hard.

I have my druthers about rebuilt units not being up to snuff with your requirements, and the reason I say spend a little more through summit or jegs for top of the line. I'm sure they have a good warranty program.

Also as a side note, Try running a "New" heavy duty ground wire to from your batteries negative to the chassis. My new walbro pump contained an additional ground wire, and in reading they said that over time the stock grounding wires sometimes deteriorates. So even though you checked all grounds, the wire itself might be corroded or weak.

Hope you figure it out. You might want to run a temporary new ground wire for starters before spending the money on a new alternator.

Good luck! :cheers:

 

Scorp and Magoo, are those voltages quoted with all the accessories running?

Magoo, what was the voltage before the Tuff Stuff alternator? How long have you had it installed? And did you have to modify anything else?......oh yeah....how much did it cost?

After reading the manual this morning, i see there is a way to bypass the regulator to test the alternator....i'll have to try that tonight.

When i start the car, the voltage gets up to near 14 and will come down to mid 13s aftewr a little while as the battery charges.....it has always been like this, but as i add these loads, i see the following voltage drops:

Cooling fan: .5-6
A/C & Fan Hi: .5-6
Headlights: .5 (w/ Fogs lights .6-7)
Brake lights: .1-2
Wipers: .1-2
Aux fan: .3-4

So if i'm sitting at a stop light with the headlights on, the A/C on hi, with a hot car so the fans are running, brake lights on, in the rain with the wipers going......I've got problems.

Jesse, the guy at the alternator shop also suggested i ck out my grounds. The smaller black wire that goes to the frame looks OK visually. I wanted to put a gold end on it, but couldn't find any yesterday. I did pull off all the ground wires and clean the terminals and the frame. The Elec pump draws about 8-9 amps and knocks the voltage down about .3-4 volts. But even if i pull the fuse on it, i'm still only about 12.0-12.2 volts with everything else going. Do you still have the broken Alt? I wonder if it's guts would fit inside my case?

I just hate to spend another $150-200 and find out it's not the alternator :mad


[Modified by ralph, 9:39 AM 8/4/2003]

 

Everything except for AC as mine isn't working. :)

 

Scorp, how about the vent fan? Mine seems to draw quite a bit and pulls the voltage down a lot more than i would have expected.

 

Hmm... I'll have to go and play with that this afternoon and get back to you. I can't ever remember it pulling a large amount though.

 

I put in a 140 amp last fall...I went for the real thing..A/C Delco..$199.00...since then I've had no problems and cruising with no access. on I'm at a steady 14.3V...with the A/C on and the fans running, stopped at a light I'm at 13.9V to 14.1V....the other plus is you can add "neons" if you care to... :jester ..good luck

 

Ralph,

Nahhh unfortunately I don't have it anymore. I know the guy at the store and he returned it as a defective unit, even though he and I know it was a result of the "lack of bracing". I since added the brace back on.

If I had it I would surely send it out to you, but I think its a little bigger by the looks of it.

I would definately run a new ground wire, for all it would take, you might find that is your problem. Walbro was very adiment on using a "new" or secondary ground. Probably because as you already know your fuel pumps output is directly related to the power it recieves.

If your whole system is down, so if your FP. Just another reason to run another one, even if its not the solution to your problem. :cheers:

Keep us all posted on what you find. I would test mine for you also, but as you know I have no car back yet.

 

Before I changed the alternator my Vette would idle at about 13.4 then dip to to around 11.8/12.1 while driving. This is without the AC on (My AC has never worked), My lights would dim big time. I went through 4 stock units in just 3 years. I did find a power drain though and can probably blame that for all those failing alternators along with a few batteries. My engine was also running very hot at the time due to cooling problems that I since fixed, Again another reason for my poor luck with alternators.
BTW I do have the Air Pump Eliminator kit too.

I bought the Tuff Stuff Alternator last May and have had great luck with it. I've only put around 2,000 miles on it so far but have yet to see a drop in power.

I can't remember how much I payed for it but I did pay extra for a chrome unit. :D

 

Ralph - No input from me on this, but I have the same issues. Now you know why I have had dead batteries at the track twice in the last 2 years.

Vic

 

I've been using a 140 altenator on my '84 for about a year now.
Bought it online from Tuff Stuff, in chrome.
Works great with my march pulleys on keeping my Idle volts cold at 14.7, and once warmed up 13.8.
Just my thoughts
tony
:chevy :cool: :chevy

 

I can pretty much thank you for influencing me into purchasing one. I love it........Thank you. :cheers:

 

Your right...but the real problem is the 105 Amp unit when new is barely capable of producing sufficient current at low engine speeds without dropping voltage. So, by upgrading to the bigger unit, your really getting more low rpm voltage/current capability.

Go for it...I did my 87 a few years ago. Its been the best money I have spent on the car to date!

As for MAX current...remember, the current supplied will only be that necessary to keep the voltage from falling off...or in short, it only supplies what your car needs at any given time. I doubt if the full load reaches 100 Amps, but its nice to have a little reserve power built in.



[Modified by BBA, 12:45 PM 8/4/2003]

 

Asside from C4396, have any of you guys run a new wire from the Alt to the battery or are you using the stock wiring?

FWIW, i was able to shoe horn in the next larger size battery. I had to cut the tray a bit and cut the handle off the battery, but i got it in there. I hoping the extra capacity will help at the track, especially with the electric water pump.