On Sun, 12 Jun 2016 18:03:43 -0500, Ignoramus13864
wrote:

On 2016-06-12, Jeff Liebermann wrote:

It was an exchange. I did not check closely when it was exchanged (my
guy went to that shop, not me).

What I know is that the pulley that I have right now is the smallest
practicable pulley.

The reason I mentioned the pulley swap is that's what happened to me
in the distant past when I bought an exchange alternator. The smaller
replacement pulley diameter was sufficiently different that the
vehicle charging system to act strangely. Over speeding the
alternator blew up the regulator several time. Then it blew up one of
the diodes, I got suspicious and checked the operating AC voltage to
the diodes. Too high. I was on my 3rd replacement alternator, all
with undersized pulleys, when I found an identical model Dodge D50
diesel and measured the pulley diameter. Swapping for the correct
pulley fixed the problems.

Incidentally, I also had oil pressure problems from the undersized
pulley. The oil pump was attached to the back end of the alternator,
resulting in excessive oil pressure. That blew out several oil
filters and one pressure regulator valve. That problem also went away
by using a larger pulley diameter.

In my days in the 2way radio business, when tube type mobile radios
drew considerable power in receive, it was imperative that
installations that spent considerable time at idle could also charge
at idle. Public safety and delivery vehicles were prime candidates.
At the time bigger alternators, with smaller pulleys were a common
solution. I wasn't involved in the conversions, but did notice a fair
number of squealing fan belts when the vehicles arrived for service.

If your alternator was an exchange, I would at least determine what is
the correct pulley diameter (and cross section for the belt).

Ummm... I know this is too obvious, but by chance did you check for a
loose and slipping fan belt? That might explain the lack of charge at
idle. Also, if the pulley wedge angle does not match the belt, it
will slip. How about the belt contact angle on the smaller pulley? My
guess(tm) is about 120 degrees minimum or it might slip.

Well, I know that it does NOT charge at idle.

Ok. You have an optical tach handy. At what RPM does the alternator
start to charge? I'm trying to determine if it's marginal or broken.

I know that by simply measuring voltage on the battery. It is about
11.76 volts when at idle. Goes up to over 13 volts if I push the gas pedal.

11.76V presumably measured between the battery terminals, is a dead
battery. Lots of SoC (state of charge) charts available:
https://www.google.com/search?q=lead+acid+battery+voltage+vs+charge+level &tbm=isch
This one looks good:
http://image.slidesharecdn.com/dscmarineelectricalsystemsseminar020311-110208132020-phpapp02/95/dsc-marine-electrical-systems-seminar-020311-44-728.jpg?cb=1297171312
11.76v is 30% of full charge. The alternator should be furiously
charging such a depleted battery. However, don't assume that it's
dead or dying. It might be that the charging system has some kind of
failure. Try charging it back up with an AC powered battery charger
and see if things start to work more normally. If you have removable
caps for a flooded lead acid battery, verify the SoC with a battery
hydrometer.

I do think that I have a good understanding of it using the
multimeter.

Assumption, the mother of all screwups. Also, test your assumptions,
which you may have noticed is my method of troubleshooting.

On a different forklift, I was able to solve it by making the pulley
diameter smaller, but here the pulley is already very small.

What problem did that solve and what problem are you trying to solve
here?

The problem was exactly the same, the other forklift also had a DD53
and the replacement alternator did not charge at idle. I was able to
make the pulley diameter smaller on a lathe and that helped.

Do you know anyone else that has a similar fork lift? There should be
some forum online where you can obtain a consensus. In other words,
are your two fork lifts the only one's with the problem? Is it a
common problem? Is it inherent in the design of the forklift? Do
other fork lifts of the same model charge at idle. Are there any
factory modifications available? I wish I could answer these, but
this type of survey is too time consuming. Googling for forklift
forums:
http://www.forkliftaction.com/forum/
http://forkliftforums.com
http://www.heavyequipmentforums.com
etc...

Here, the pulley diameter is already small and even smaller diameter
will ruin the belt.

Yep. See my comment above on the squealing fan belts in the old
vehicles which had modified pulleys.

It definitely needs to charge at idle.

How much charging current would you guess might be required at idle?
That will tell my how far up the RPM curve you will need to spin the
alternator. If you could disclose both pulley diameters, I can
calculate the required engine idle RPM. If too high, it might not be
possible. Let's use this curve until something better can be found:
http://www.thesolar.biz/Balmar%2070-SeriesDIMENSIONS.jpg

I was looking at changes in battery voltage.

Bad idea. You should see a change when revving the engine, but you
can't use the voltage as an indication of charging current. For that,
you need an ammeter. Also, the voltage does change with temperature.

At idle, the battery voltage is exactly the same as when the engine is
off.

That's a good indication that it's not charging at all.
http://www.aa1car.com/library/charging_checks.htm
At idle, most charging systems will produce 13.8 to 14.3 volts
with no lights or accessories on (although some may charge
at a slightly higher voltage depending on temperature, engine
RPM, type of battery, and the battery's state of charge).
11.76V is MUCH too low.

I just bought an ac/dc clamp ammeter, it might help me in the future,
but I do feel strongly that the DC voltmeter is telling me all I need
to know.

Many clamp on ammeters do NOT measure DC current. As I mumbled
previously, voltage is not a good indication of what's happening,
although it does offer some clues. In this case, you seem to be
ignoring an obvious clue. 11.76V is MUCH too low for proper
operation. Assuming the battery is good, something else is seriously
wrong. I can't tell from here, but my sense of smell says it's a
blown fusible link, or rotten terminal connection on the alternator.

Also, it would be very helpful if you would kindly supply numbers. By
numbers, I mean measured voltages, measured currents, the maker and
model of your clamp on ammeter, the maker and model of your
alternator, the maker, size, and model number of your battery, pulley
diameters, and so on. The quality of the answers that you get will be
directly related to the quality of the information that you provide.
Numbers always are a big help.

Good luck.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558