Date: Sat, 27 May 2006 11:32:57 -0700
Reply-To: Mark Drillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mark Drillock <mdrillock@COX.NET>
Subject: Dash wierdness, was- Aux Battery.....
In-Reply-To: <00db01c681a6$ec538a90$6600a8c0@tomsp4>
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As I have pointed out before, one of the weaknesses of the Vanagon that
shows up more all the time is the dash grounds. VW connected a lot of
unrelated stuff in the dash to the same ground wire. When that ground
wire connection develops corrosion over time, strange things happen and
can drive us crazy. In particular, VW should have kept the cig lighter
socket ground isolated from the rest. Of course way back then, few
people used the cig lighter socket for much of anything except
occasional light of a cigarette. Now we tend to have other stuff plugged
in and powered up by that socket much or all of the time.
With a weak connection at this one common ground point, the various
circuits that use it can get a bad ground reference or even have current
flowing backwards in some wires. The stuff in the instrument cluster
needs a good ground. Not having it can cause indicator lights and the
temp and fuel gauges to misbehave.
Mark
Tom Salicos wrote:
> A few weeks ago I passed on what I now believe is not good advice about feeding the Fuse 3 position on the fuse panel to power the radio, westy and dome lights. I found somebody's post on doing that and I thought it was really slick, but have since had an experience that caused me to change my mind.
>
> I ran a 10 gauge fused wire from the aux battery under the carpet, up to the fuse panel. Then I intentionally blew a spade fuse and soldered the wire to one spade of the ex-fuse that was now a plug. This ran the radio, Sirius receiver, Westy and dome lights okay. In fact I ran the radio all day while working in the yard, just to stress test my new aux battery a bit.
>
> Unbeknownst to me at the time, the aux battery was not getting charged when I drove.
>
> I drove to work and the radio started cutting out. Then wouldn't work at all. Then on the way home, on that warm but not hot day, my coolant LED started flashing. My IR meter said coolant temp was okay and the burp tank level was good. So I finished the trip home.
>
> I checked the voltage on the aux battery and it was down to 6 volts. I'll speculate that the circuit that fires the high coolant warning uses a reference level derived from Fuse 3 voltage, and lowering the source voltage caused the overtemp warning to fire way too low.
>
> I fixed the charging problem and got the aux battery back to snuff. Would re-source the audio power later. I had trouble clearing a code from the Subaru ECU so I decided to disconnect the main battery ground and do it the easy way. Code didn't clear. Hmmm.... Seems lots of stuff comes off of Fuse 3 and feeding it as I did puts two different sources of power under the dash. Not healthy I think. Yes, I should have checked the Bentley, but hey, I read the tip on the Internet, so it must be good, right?
>
> I have since connected the radio and Sirius up properly. I also have installed a switch that allows me to run the audio equipment when the key is off. Diagram for that is here:
>
> http://www.salicos.com/images/AudioHookup.jpg
>
> I am also working on an aux battery web page. The scholarly dissertation to date is here:
> http://www.salicos.com/SecondBattery.htm
>
>
> Have a happy Decoration Day !
>
> Tom Salicos
> '87 Syncro Westy EG-33
>
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