TRF Summer Party first:
Anyone else going to the TRF summer party? I plan to leave later
today (thursday) and will be there with my wife (Linda) and son
(Sean). We will be there with a pair of 1981 Triumphs, both
are bordeau red (maroon). Mine is a TR-8, Sean's is a TR-7.
We will be camping at TRF itself. No response is requested via
email as I'll probably be outta here by noon today. If you are
there at all, do say hello to this fellow SOL.
Now, on to the electrical problem.
Don Adams problem:
> Whenever the electric fans kick in to cool off the coolant in my
> radiator my system voltage drops to about 10.8v. As a result when
> other things need voltage (vs current) to function properly such as
> the turn signals, dash lights etc they are marginal if operable at
> all. I suspect that the current draw from the fans is too high for
> either my alternator or my battery but am unsure as to which. Has
> anyone overcome this problem?
> I would appreciate any experiences you have with this problem.
A properly operating electrical system should work as follows:
Assuming the battery is fully charged and the vehicle engine
speed is in the normal (not idle) rpm range (generally anything
over 2000 rpm.) the alternator's electrical output will vary
depending on the total current required to operate the various
electrical components that are on. The maximum output (in amps)
of the alternator should be greater than the total current required
to operate all the electrical components at one time. In other
words,
words, if the car is being driven, the battery should still be
receiving some charging current and ALL the current required
for the car's electrical stuff is coming from the alternator.
In Don's case, several possibilities exist:
1. One of the fans (or the electrical circuit for the fans)
has a short (probably not a dead short or the car would
likely burn up the wiring.) That short or propblem fan is
drawing more (much more) than it normally would which is
exceeding the alternator's output capacity.
2. The alternator has a problem in that it is unable to
provide its full current output capacity. Alternator's
have diodes in them that convert AC electrical power
to DC that is required for the vehicle's electrical system.
There are usually (I think) 4 diodes in an alternator.
If one or more are bad, the output capacity of the
alternator is reduced.
3. There could be a short somewhere else in the electrical system
that is constantly drawing current and when the fans are on
the total current load placed on the alternator exceeds the
alternator's rated maximum output.
Having said all that, a few "troubleshooting" questions are
offered. Does the voltage drop to 10.8v with the headlamps
off? If it does, what happens when the fans are not on
and you put the lights on? If the lights alone do NOT cause
a the voltage to drop below 12.6v (Nominal battery voltage),
then I'd be very suspect of the fans (or the fan circuit).
Since you have Two fans, try disconnecting each one separately
to see if one or the other is the problem.
If you can, try getting a hold of a "Clamp-on Ammeter."
Using the clamp-on ammeter on the output cable of the
alternator will give you a good set of readings on the
health of the alternator.
Hope this helps some.
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Bill Sohl (K2UNK) || email
Bellcore, Morristown, NJ || UUCP bcr!taichi!whs70
(Bell Communications Research) || or
201-829-2879 Weekdays || Internet whs70@taichi.cc.bellcore.com
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