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Re: Cory's mysterious relay

To: british-cars@autox.team.net
Subject: Re: Cory's mysterious relay
From: acg@hermes.dlogics.com
Date: Mon, 10 Aug 1992 14:35:36 CDT
Cory Carpenter <coryc@sequent.com> writes:
> This would also explain why the charging system would suddenly start
> working again after the car had been sitting for an hour or so -- the
> charge in the battery would rebound enough to keep the relay closed.

I'm having problems trying to follow this part. If I was designing a system
like this (and I wouldn't ;-), I'd have the actuating current for the relay
come from the alternator, not from the battery. That way, as long as the
battery has enough oomph to close the contacts in the first place, the juice
from the alternator would then hold them closed from then on. According to
what you describe, current to hold the relay closed appears to go from the
alternator to the battery, THEN from the battery to the relay coil. This
makes no sense to me.

If we're talking about some really crude early design here, let me hypothesize
about what's going on:

1) Driver turns ignition on; battery energizes alternator relay via wiring
   run through ignition switch.
2) Engine starts; alternator supplies power to system and recharges battery.
3) Upon engine shutoff, when driver cuts ignition, power to relay is cut off.
   Relay opens and (this is the hypothesis part coming up, folks!) cuts all
   electrical power to engine from alternator. How it would prevent power in
   battery from running engine, I'm not sure.

-- Andy


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