High Output Alternator?
 

Hello everybody, so I have a 79 240D and I just did the Duraterm kit on it (found one brand new after a long time searching). Now every week or so it wont start. The battery is drained to the point it will only rotate the engine about once and its done. This all starting after putting the kit on. The alternator is charging at 13.8-14V at an idle. The battery has been load tested and is in good shape. Im thinking with the prolonged time that the relay runs its not charging well enough during my drive to work (5 min) and that's my problem. Is there a company that makes a good high output alternator for these cars? Any help would be appreciated. Thanks.

Hi 79'_240D, welcome to the forum.

I just upgraded my alternator to a 115 amp Bosch AL129X in this thread:

http://www.peachparts.com/shopforum/diesel-discussion/364297-diy-al129x-alternator-1978-w116-300sd.html

Squiggle Dog upgraded to a 80 amp Bosch AL69X alternator in this thread:

http://www.peachparts.com/shopforum/diesel-discussion/335086-installing-upgraded-80-amp-alternator-9-blade-fan-1980-w116-300sd.html

This forum has a lot of great information that can be accessed by the search function or by simply asking for help.

Best of luck on your upgrade. Keep us posted of your progress.:)

What are the characteristics of your Duraterm conversion? How many amps does it draw? What is the on time per cycle?

Upgrading an alternator isn't hard, but to go to something like a 115A alternator is more of problem than a solution. More than 100A, and you really should be using a serp belt rather than a V belt, and you need to upgrade the wiring between the alternator and battery.

What amperage alternator is on it now and can you test it to see if it will produce its full amperage rating? Check to see if the alternator belt is slipping, if the belt pulley on the alternator gets very hot, the belt is slipping.

Is driving it more to charge it an option?

What is the current draw when everything is off? Thinking of a shorted circuit or leaky diode...

Good luck and keep us posted!!!

Driving for 5 minutes after a cold start is not enough to charge the battery IMO , even if you upgrade to a higher output alternator. You need to drive it longer to charge the battery. Can you take a bus, a bicycle, or walk instead?

...or take the scenic route...or a motorcycle...or a Tesela...or get a battery charger...or move further away...or get a different job...

Thanks for the threads guys I will look into those options. Im not looking for a cure all. I know it probably needs to probably be driven longer but thats not really possible. This problem only happened after I put that post glow relay on. And just so ya know I dont walk in -20* temperatures. During the summer I ride my trail 90.

In -20 temps, are you plugging in your block heater?

If so, add a hardwired battery charger to your setup too. Charge your battery while your block heater is plugged in.

Couple things that haven't been mentioned so far-

If you alt is charging with correct voltage, what would getting a high output alternator do? Isn't a high output alternator for when you're running so much stuff it can't properly charge? I just did the Bosch 115 alt upgrade myself, but my alternator was dead.

Another suggestion not mentioned- a turbo timer. Whether you have a turbo or not, you could easily install a turbo timer (prices vary to very cheap to very expensive). This will let you set almost any set amount of time to leave the car on after you have pulled the key. So, you could drive for 5 minutes and then let it idle in the parking lot unattended for 10+ minutes - however long you so desired. This might be healthier for your car as well as your battery.

Did the problem exist before you put the duraterm kit on? If not, perhaps you should remove it. What was the reason for putting it on in the first place?

Careful what you do. In one of those threads, the poster replaces the pulley with one that happens to be larger. Although beatuifully executed, the alternator is under-driven. Under driving an 85 amp alternator this way would give you the performance of a 55 amp alternator.

The output of an alternator is usually quoted at 5000 RPM (alternator RPM is 2-3 times engine RPM). At low rotational speeds, an 85 amp alternator doesn't make much more power than a 55 amp alternator. I'm attaching performance curves for various Delco alternators (sorry, I don't have bosch curves) so you can see what I mean.

This is something I've been wanting to do for quite a while. The alternator in my 220D is kind of anemic with an output of only 35 amps. An 80 or 100 amp unit would be nice so I could run a good amplifier on my radio without worrying about overloading the charging system.

I take it these later Bosch units just bolt in with nothing but a modified plug?

^ Rewire signal wire and the positive wire to handle more juice. Also need to swap the metal fan blade from the current alternator to the new Bosch one (which is *slightly* too large and will foul).

Same here. I've been researching it for the day mine dies. I don't necessarily need it, but I don't want to spend a dime on a 35 amp alternator.

From what I've seen, all these newer units have a top adjusting bracket. The ear on the alternator is thick to accommodate a big bolt going through.

We have a small adjusting bolt and small ear on top. Btw, has yours broke yet? I took some flat stock and pounded away until I got the right shape. Slotted a hole in, and use i big pry bar to tighten it down.

I'm not sure how these others will fit. I've been meaning to take an old broken one I have into the repair shop and just look around at their stock. Those guys will probably know what to do with a glance

I would like to make or adapt a top bracket like that. Will see. I have a 280 motor coming eventually (unless shortsguy sees this and gets the idea). And am curious what the alternator is. The car had power windows and such, it may be more.

Let me know if you make progress on it. Curious.

I doubt the need is present for a high amp alternator... more likely yours is worn and not producing power.

"load testing" a battery is rarely a good option. how old is the battery? what is the CCA percentage on a true digital test? how new is your alt belt? you might want to put a clutched fan on from a 617 motor to reduce the loads on the belt...
in -20 temps, the starter REALLY has to work to start the car... toss in the 4 duraterms, and afterglow, and yeah it'll drain a weak battery in short order, toss in a short drive, worn belts, and a worn regulator... and in very little time, the car won't start.
you could also have a parasitic drain.
I certainly agree that the car should be plugged in, and a trickle charger or maintenance charger should be wired in to the battery to keep it full at night...