It is normal for the battery voltage to drop to about 10v during cranking
even on a good battery, lower still with a weaker battery or bad
connections. It is also normal for electronic devices to have a point below
which they 'switch off', instead of 'browning out' like simple electrical
devices. 2ndly you may have bad connections in the low current wiring which
results in low voltage to the electronic devices during normal running,
which gets 'catastrophically' low during cranking. 3rdly they may be wired
to the 'accessories' position of the ignition switch which loses its 12v
supply during cranking anyway. Measure the voltage on the brown during
cranking - you may need to use an analogue meter to be able to get a
reading - and see how close yours is to 10v. If that is what you see then
stop worrying and JFDI. If 9v or less take another reading direct on the
battery posts and see what you get. If much the same then either the
battery is weak or some other effect of the engine is putting too much load
on the starter. If 10v or higher then you have bad connections between
battery and starter, or possibly your battery cable has been replaced with
an inadequate item. To check the connections and cable put one probe of the
voltmeter on the hot post (not connector) of the battery and the other on
the hot post at the solenoid and measure the lost voltage during cranking,
and again between the ground post of the battery and the starter body. If
you have twin 6v batteries also do it on the battery posts that carry the
link cable. Ideally you are looking to lose only a couple of tenths of a
volt lost in the connections and the cable(s). If you see getting close to
1v or worse then it is worthwhile investigating the amount being lost in
each connection and the cable and cleaning up bad ones.
All of which is nothing to do with electrical noise, particularly when
everything else is switched off. What makes you think you have that
problem?
PaulH.
----- Original Message -----
From: "James Nazarian" <jhn3@uakron.edu>
To: "Rick Lindsay" <rolindsay@stoolhead.com>; "mgs" <mgs@autox.team.net>
Sent: Saturday, December 27, 2003 8:09 AM
Subject: Electrical Noise
> While installing XM in my V8 the other day, I accidently discovered that I
> have a source of noise in my electrical system. The puzzling part is that
> it is present even when the car is not running. The details are a bit
foggy
> at the moment because I haven't had the opportunity to fully investigate
it.
> For now I'll stick to asking one question...
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