Alternator options? - PeachParts Mercedes-Benz Forum

RichardLSU · #1 09-25-2010, 04:58 PM

I recently got the a/c in my car working again and have since had a dead battery problem. I replaced the alternator because I knew my old one was on its way out. The battery is a Red top Optima, less than a year old.

The new alternator didn't help. I've been driving with my fan on low with the a/c on and sometimes cut it off about a half mile from my destination, this seems to be working. Occassionally though its still not enough and I end up calling someone to give me a jump.

Has anybody else had this problem? Are there any solutions? The biggest alternator I could find was a 60kw one from Oriellys.

Gonna try to find a smaller pully or something!

sixto · #2 09-25-2010, 05:18 PM

60kw or 60 amps? 60kw is a lot!

http://www.peachparts.com/shopforum/showthread.php?t=93569

http://www.peachparts.com/shopforum/showthread.php?t=53236

[edit] But I don't think you have an alternator problem.

Sixto
87 300D

Diesel911 · #3 09-25-2010, 05:41 PM

Please note this comment from the Link below:
"My Pantera has an Optima battery, which needs a charging voltage between 13.8V and 15V."
http://www.detomaso.nu/~thomast/alternator/

At idle you are lucky of you get something like 13.4-13.5 volts; and this is without any excessories running.
If the Link is correct this is below what an Optima Battery needs to charge.

RichardLSU · #4 09-25-2010, 07:18 PM

Whoops! 65 amps!

69shovlhed · #5 09-25-2010, 08:36 PM

optima battery in my chevelle w/ a small crank pulley; it will discharge at idle. never needs a jump unless it sits for more than 2 months without starting it. alternator must not be charging at all for some reason, or there is a short or wiring problem. first, i'd check the quiescent current draw at rest. should be no more than 30mA. then check charging voltage at idle and 2000 rpm. should be >13v. check all the ground straps and cables to verify engine, battery, alternator, etc are all properly grounded together.

RichardLSU · #6 09-25-2010, 09:17 PM

At idle Im getting about 13v, which is just about breaking even. With the compressor, fan, lights, radio etc... on its not charging anything. When I get out and drive around it charges, but like I said, sometimes its not enough.

Im thinking about calling some auto electric shops to see if they can modify it to put out more.

micalk · #7 09-25-2010, 09:38 PM

look for alternator threads in the forum. alot of people put in a Bosch AL129X which is a 115A alternator, more than enough power for most, and should boost your voltage at idle.

However, I agree with sixto that a good 65A alternator shouldn't have a problem with a stock electrical system and should deal with the a/c without the battery going dead. You need to check out your system and find the source of the discharge problem.

Diesel911 · #8 09-25-2010, 11:37 PM

Quote:

Originally Posted by RichardLSU

At idle Im getting about 13v, which is just about breaking even. With the compressor, fan, lights, radio etc... on its not charging anything. When I get out and drive around it charges, but like I said, sometimes its not enough.

Im thinking about calling some auto electric shops to see if they can modify it to put out more.

If all the links work in the below thread you will see how a Regulator can be modified by adding a Diode to the circuit to increase the Voltage output.
http://www.peachparts.com/shopforum/showthread.php?p=2427184#post2427184

As previously stated the real cure is to update with a more modren Alternator that has more output to begin with.

In the mean time the Electrical shop my have an Oscilloscope that could tell if you have some bad Diodes inside of the Alternator. They also might have a smaller Pulley.

pimpernell · #9 09-26-2010, 09:10 AM

Quote:

Originally Posted by RichardLSU

I recently got the a/c in my car working again and have since had a dead battery problem. I replaced the alternator because I knew my old one was on its way out. The battery is a Red top Optima, less than a year old.

The new alternator didn't help. I've been driving with my fan on low with the a/c on and sometimes cut it off about a half mile from my destination, this seems to be working. Occassionally though its still not enough and I end up calling someone to give me a jump.

Has anybody else had this problem? Are there any solutions? The biggest alternator I could find was a 60kw one from Oriellys.

Gonna try to find a smaller pully or something!

My alternator bit the dust last year, and after checking around, I purchased a "new" NSA one from Ebay. The price was about the same as a rebuilt, came with its own pulley, and was brand new. The only thing I had to do prior to instillation was change out the pulley. My old alternator had what is called a "free wheel clutch pulley" which is designed to even out the rotation of the alternator, taking into account the power stroke of the engine. With the glow plug relay engaged when first starting, it puts out about 12 volts. Once the glow cycle is complete, it jumps up to 13.5-13.8. With everything running, lights, ac etc. it holds steady at 13.4-13.6.

http://www.nsaproducts.com/products.html

RichardLSU · #10 09-26-2010, 09:49 AM

Yeah, I just replaced my alternator with a new "rebuilt" one, got the lifetime warranty too. I did have to switch out my pulley as well.

69shovlhed · #11 09-26-2010, 11:32 AM

Quote:

Originally Posted by RichardLSU

At idle Im getting about 13v, which is just about breaking even. With the compressor, fan, lights, radio etc... on its not charging anything. When I get out and drive around it charges, but like I said, sometimes its not enough.

Im thinking about calling some auto electric shops to see if they can modify it to put out more.

13v is that w/ everything turned on or off? if its w/ all your accessories running, thats not great but it's still charging a little. and how much voltage at 2000 rpm? you need to know if the voltage increases w/ rpm. turn everything on and check the voltage at idle and at 2000+. you won't know anything until you check it at cruising rpm w/ all loads on.