Date:         Wed, 06 Jul 94 20:13:40 CDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Joel Walker <JWALKER@ua1vm.ua.edu>
Subject:      Re: alternators

On Wed, 6 Jul 94 12:50:17 CDT Alistair Bell said:
>My interest stems from the installation of a voltmeter in
>my van, and noticing that my 90 amp alternator's voltage
>output would drop to 12 volts if I had the heater blower,
>wipers, lights and rear defrogger all on, and drop below
>12 if I tried the cig. lighter. The combined current draw, I
>think, is under 80 amps. Asking around, other vw drivers with
>voltmeters seem to think this is normal, but...

hmmmm. oh, wise and wonderful Bosch, what sayest thou? <crossing his palm
with silver ...>
heater blower (fan motor):         50 watts (average power consumption)
wipers (another motor):             5 watts
lights:                            90 watts
rear defrogger (high resistance):  34 watts
                                  179 watts (15 amps)
cigarette lighter (high resist):  100 watts (8 amps!!! by itself!)
and don't forget the 'normal' stuff:
battery ignition                   40 watts
instrument panel lights             5 watts
license plate, tail lights         30 watts
side-marker lights                  7 watts
                         --------------------
                 grand total:     361 watts or 30 amps.
so, yeah, i'd say that ought to drop the voltmeter down a bit. :)

i think i'd get me a Bic lighter.  especially since i have two 7" fog lights
and two 7" driving lights on the front, with a 5" red fog light on the rear
bumper. now, i don't normally run all five of those (in addition to my
normal headlights and side marker, license plate, and tail lights), but i
have run along  with two of them burning. they are wired with 'pop' circuit
breakers (from a Cessna) at 10 amps each, and the data that came with them
says they run about 5 amps each (7 amps to start up). Make Light the Night!!

>Maybe the reg is weak or the alternator is (although it was
>tested before installation), or maybe I do have to spend
>an afternoon soldering all the important connections, or
>maybe I shouldn't try lighting i cig. whilst driving
>in a cold rainy night.

i'd bet on just 'normal' voltage drop, being accumulated round the bus. as
i understand it, if a wire is NOT large enough in diameter, the voltage will
'drop' between the battery and the consumer (light, fan, whatever).

example: in the headlight circuit, bosch says that 0.5 volts is 'permissible'
from the switch to the light, and 0.9 v is 'permissible' in the entire
circuit. now, vw is no different from other companies, and bigger, longer
wires cost extra money, especially when you are building Millions of cars.
if you can save $1.00 on each car by making the wire 18 gauge (instead of the
larger 16 gauge), you just save the company a million bucks.

so what to do? well, as i understand it, the biggest offender is the ground
wires. especially since part of the ground circuit is the chassis.  so if
you ran a large (12 guage wire) from the ground wire of each headlight back
to the battery ground-chassis connection, you would DEcrease the voltage
drop in the headlights (AND get brighter headlights!).

well, i 'never got around' to trying that, but i did do the starter on my
1980 bus (round about the solenoid failure time). i ran a pinkie-sized wire
(about 1/2 inch diameter, including insulation) from the battery-chassis
ground bolt under the car to the starter mounting bolt. propane-torch-soldered
the connectors (OFF the car, thank you!). and it made (i think) a noticeable
difference in the speed of cranking.

so why didn't i do it to the lights and everything else? well ... cause it
was just such a damn pain to work with that big wire! a royal difficulty.
but i keep thinking about it. maybe a 1/4 inch wire for the headlights and
taillights and wipers and so forth. one of these days. do as i say do ... :)

and, besides ... everything on MY bus works pretty good. :)

BUT! a point for all older microbuses and buses and vanagons to consider
(you eurovans are just too new to worry about this):

as the years roll by, you'll get extra resistance in the circuits, due to
chassis rust/age/whatever and connector corrosion. so maybe such direct
ground paths would be of benefit to, say, a 1980 vanagon or 77 bus. i got
the idea from a HOT VWs article talking about 60's beetles. :)

hope it helps.
joel