Date: Mon, 28 Jan 2013 15:32:31 -0800
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: Now: Jetta ECU-Coil Amp Draw Was: Ignition Switch "Su"...
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Hi all. This is for a 1981 formerly air cooled Vanagon with a self
installed Jetta 2.0 OBD1 engine.
My good DMM (20 Amp rated) had a blown fuse so I took a chance using
my 10 Amp rated DMM.
With DMM connected in series between 30 (B+) and 30 of an added relay
to carry power to ECU and coil, engine cold, DMM set to 10 Amp scale:
engine off: no current draw (makes sense)
idle: 1 - 1.5 Amps
2K RPM: roughly 2.5 Amps which increased as RPM increased. Highest
was about 3K - 4K RPM.
I also ran the test with the new relay UN-installed; DMM in series
between 30 and coil/ECU wire, effectively bypassing the ignition
switch. Same results. (btw. When I inserted the DMM probe to meter,
the fuel pump primed each time I made the connection. I'm certain that
supplying + to 38 of ECU energizes the ECU so that it can energize the
fuel pump relay by supplying a ground)
This is somewhat embarrassing!
Unless I'm doing and reading things wrong, well, even though it's a
long wire, I guess the OEM #16 wire should handle the load(s) created
by the Jetta ECU and coil. Like one chart shows #16 wire at 12 Volts,
10 Amps, has a maximum length is 25'. And, any increased wear and tear
on the Vanagon ignition switch is likely small, they fail at some
point regardless, so I highly doubt any of this caused the mysterious
highway speed stall I had.
Caveat: I have NO idea if increases in engine temperature, ambient
temperature, etc. would affect the actual current drawn. i.e. in a
real life driving scenario. Also, I am not a scientist, electrician or
qualified in any other related way. ;^)
The instrument cluster was not connected to the 15 circuit while
testing so the VSS, dynamic oil pressure board, etc. did not load the
circuit. My guess is that any current increase due to those parts
would likely be negligible.
Thanks
Neil.
On Sat, Jan 26, 2013 at 3:50 PM, Scott Daniel - Turbovans
<scottdaniel@turbovans.com> wrote:
> how much current do you figure your ECU draws ?
On Sun, Jan 27, 2013 at 1:10 PM, Ryan Press <ryan@presslab.us> wrote:
> I think it would help if we knew how much current the ECU actually draws,
> and how much the coil draws. Can you measure these with an ammeter both
> while running and not?
--
Neil n
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