13,8 V idling charging voltage ok ?

#11

"franz47" <roskakori (AT) gmx (DOT) net> wrote

Quote:

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h74shv$qcn$2 (AT) news (DOT) eternal-september.org...

Also are you checking the voltage on the output terminal of the
alternator? There may be a bad connection somewhere if it is low
elsewhere.

As usual James is right!

I took the time now to have a closer look. The voltage at the alternator
terminal was 14-14,1 Volts, exactly as it should be according to the
regulator specs. There is a 0,3 V voltage drop between the alternator
terminal and the cable terminal at the battery.

Although I removed the cable from the alternator terminal, sprayed it with
electrical contact spray, cleaned it with fine sandpaper, the same with
the surface of the nut pressing the cable terminal to the alternator
terminal - nothing changed. The cable terminal on the alternator is
connected with the cable in a way I cannot do much about. Maybe there is a
resistance. On the battery side the cable turns into a terminal without
much to do either. The voltage drop is already at the battery cable
terminal. There is no more voltage drop between cable terminal and battery
terminal. The cable disappears form the alternator into the depth of the
space - is there a connection at the starter which could be the culprit?

Franz47

There will always be a voltage drop over a length of conductor when there
is current flowing, The drop (V) depend on the current (A) and the
resistance (Ohm).
Do not forget the negative part of the cirquit.
I am not familiar with all Volvo solutions at the alternator end, but at the
battery end we have the cable from the negative battery terminal to the
ground (chassis or transmission). That should be checked at both ends.
And for the positive part you probably could run an additional cable
directly from the alternator to the battery terminals, that is what the
experts did on my Toyota.
Any comments James ?

Asbjørn

#12

"Asbjørn" <asbjust (AT) frisurf (DOT) no> schrieb im Newsbeitrag
news:h799sg$s2j$1 (AT) news (DOT) eternal-september.org...

Quote:

There will always be a voltage drop over a length of conductor when there is
current flowing, The drop (V) depend on the current (A) and the resistance
(Ohm).

I did not measure current to the battery plus, then I could calculate the
resistance. 0,3 V voltage drop still eems to be quite a lot for a thick copper
cable connection of such a short distance. I will measure on another car.

Quote:

Do not forget the negative part of the cirquit.
I am not familiar with all Volvo solutions at the alternator end, but at the
battery end we have the cable from the negative battery terminal to the ground
(chassis or transmission). That should be checked at both ends.

I could measure a voltage of 0,3 Volts between positive alternator terminal and
positive cable/battery terminal at the battery. Any resistance on the negative
side of the circuit cannot influence this result.

Quote:

And for the positive part you probably could run an additional cable directly
from the alternator to the battery terminals, that is what the experts did on
my Toyota.

I think I will have a look at a possible connection at the starter between
alternator and battery, if it is accessible from above.

Franz47

#13

franz47 wrote:

Quote:

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h74shv$qcn$2 (AT) news (DOT) eternal-september.org...

Also are you checking the voltage on the output terminal of the
alternator? There may be a bad connection somewhere if it is low
elsewhere.

Good idea. Quite difficult to get there. I had a look today, no nut
visible at the alternator terminal, everything insulated. How would I
get access there to the terminal? BTW is it necessary to remove the
whole alternator to change the regulatur-brushes unit?
Franz47

There's a black cap that pops off the back of the output terminal where
the big red wire attaches.

Depends on the car, 740 you can easily change the brush pack/regulator
with the alternator in place. Most 240s you can too, but the turbos are
a lot tighter down there.

I've never had to replace the alternator itself, they're quite dependable.

#14

franz47 wrote:

Quote:

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h74shv$qcn$2 (AT) news (DOT) eternal-september.org...

Also are you checking the voltage on the output terminal of the
alternator? There may be a bad connection somewhere if it is low
elsewhere.

As usual James is right!

I took the time now to have a closer look. The voltage at the alternator
terminal was 14-14,1 Volts, exactly as it should be according to the
regulator specs. There is a 0,3 V voltage drop between the alternator
terminal and the cable terminal at the battery.

Although I removed the cable from the alternator terminal, sprayed it
with electrical contact spray, cleaned it with fine sandpaper, the same
with the surface of the nut pressing the cable terminal to the
alternator terminal - nothing changed. The cable terminal on the
alternator is connected with the cable in a way I cannot do much about.
Maybe there is a resistance. On the battery side the cable turns into a
terminal without much to do either. The voltage drop is already at the
battery cable terminal. There is no more voltage drop between cable
terminal and battery terminal. The cable disappears form the alternator
into the depth of the space - is there a connection at the starter which
could be the culprit?

Franz47

0.3V is not very much given the current potentially involved. The wire
does connect to the starter, along with another wire that goes to the
battery.

#15

franz47 wrote:

Quote:

"Asbjørn" <asbjust (AT) frisurf (DOT) no> schrieb im Newsbeitrag
news:h799sg$s2j$1 (AT) news (DOT) eternal-september.org...

There will always be a voltage drop over a length of conductor when
there is current flowing, The drop (V) depend on the current (A) and
the resistance (Ohm).

I did not measure current to the battery plus, then I could calculate
the resistance. 0,3 V voltage drop still eems to be quite a lot for a
thick copper cable connection of such a short distance. I will measure
on another car.

Do not forget the negative part of the cirquit.
I am not familiar with all Volvo solutions at the alternator end, but
at the battery end we have the cable from the negative battery
terminal to the ground (chassis or transmission). That should be
checked at both ends.

I could measure a voltage of 0,3 Volts between positive alternator
terminal and positive cable/battery terminal at the battery. Any
resistance on the negative side of the circuit cannot influence this
result.

And for the positive part you probably could run an additional cable
directly from the alternator to the battery terminals, that is what
the experts did on my Toyota.

I think I will have a look at a possible connection at the starter
between alternator and battery, if it is accessible from above.

Franz47

The connection at the starter should be accessible, you'll have to
refresh my memory as to what sort of Volvo this is. You also might see
if you can get a probe in to the exposed copper wire immediately before
the terminal and measure between that and the terminal to see if you
have a bad connection there.

#16

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h7afb0$uq2$4 (AT) news (DOT) eternal-september.org...

Quote:

The connection at the starter should be accessible, you'll have to refresh my
memory as to what sort of Volvo this is.

855 TDI 1996 December (in VADIS I find it only under 1997) with
D5252T MSA 15.7 diesel engine and
AW 50-42 automatic transmission.

Franz47

#17

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h7af57$uq2$2 (AT) news (DOT) eternal-september.org...

Quote:

There's a black cap that pops off the back of the output terminal where the
big red wire attaches.

Thanks for the tip. I found that, when I had a look yesterday under better
illumination.

Quote:

Depends on the car, 740 you can easily change the brush pack/regulator with
the alternator in place.

In the 855 one has to pay the price for front wheel drive and engine mounting 90
degrees to driving direction.
I still have another 745 TD 1989, which I have used many years and my wife now
ses in the countryside. I have changed the brush-regulator there, really a
breeze. Plenty of space around the engine.

Quote:

I've never had to replace the alternator itself, they're quite dependable.

Not me either since my first car with an alternator, a Citroen 2CV in the
seventies last century. Not even mechanical parts have failed. I just changed
the brushes once a while in these alternators, nowadays including the regulator
unit, making it much more expensive. The regulators are overpriced, for the
money the tiny little, probably very primitive circuit costs, I can get a b/w
laser printer with duplex unit...

Regards Franz47

#18

franz47 wrote:

Quote:

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h7afb0$uq2$4 (AT) news (DOT) eternal-september.org...

The connection at the starter should be accessible, you'll have to
refresh my memory as to what sort of Volvo this is.

855 TDI 1996 December (in VADIS I find it only under 1997) with
D5252T MSA 15.7 diesel engine and
AW 50-42 automatic transmission.

Franz47

Ah, I'm not gonna be much help with specifics then, unfortunately the
last Diesel powered Volvo to reach this continent was the '86 760.

I'm actually surprised I haven't heard of anyone importing an 850TDI,
but I've yet to see one in the US.

#19

Quote:

Not me either since my first car with an alternator, a Citroen 2CV in
the seventies last century. Not even mechanical parts have failed. I
just changed the brushes once a while in these alternators, nowadays
including the regulator unit, making it much more expensive. The
regulators are overpriced, for the money the tiny little, probably very
primitive circuit costs, I can get a b/w laser printer with duplex unit...

Regards Franz47

At least in the case of the older Bosch alternators, you could get a
brush pack meant for even older ones that work with an external
regulator. I've seen late 80s 700 series cars retrofitted with late 70s
style external regulator. I don't know what sort of alternator an 850
uses though.

#20

"James Sweet" <jamesrsweet (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:h7aiqp$el6$2 (AT) news (DOT) eternal-september.org...

Quote:

I'm actually surprised I haven't heard of anyone importing an 850TDI, but I've
yet to see one in the US.

I don´t know which kind of gas guzzlers the gasoline versions of the 850 are,
but the 2,5 l Audi TDI diesel runs on about 6,5 - 7 liters/100 km (makes 36 -
33,6 mpg), which was good fuel economy at that time for that car size.
Franz47