[DeTomaso] Temp Gauge Rise

Rob Dumoulin rob at dumoulins.net
Tue Apr 27 08:56:04 EDT 2010


I ran into a similar issue with on old Porsche of mine.  The oil pressure
gauge was showing very low and I was concerned.  I hooked one directly to
the sending unit and determined it was a problem with the gauge or wiring.
 When I added a ground to the daisy-chain near the oil pressure gauge, the
problem went away and it also helped others read differently (correctly, I
hope).

I haven't seen the problem with #1488, but listening to you, I suspect I
just don't realize it.  I'll add the wire this weekend and share
before/after readings.

On Tue, Apr 27, 2010 at 8:37 AM, <MikeLDrew at aol.com> wrote:

>
> In a message dated 4/27/10 4 05 18, wdemelo at cogeco.ca writes:
>
>
> > Another fellow on the PI board has reminded me of a similar problem I'm
> > having. My temp gauge rises considerably ( 15-20 deg) when I raise my
> > headlights. I was thinking it was induction in the wiring, but I beleive
> the
> > headlight switch only carries the current of the relay coil, which is
> minimal.
> > Any suggestions?
> >
>
> We covered that here in the not-too-distant past; I may have even asked the
> question myself.   It's a rather common problem (my Pantera does it too).
> You'll note that all the minor gauges except the ammeter are affected the
> same way, to varying degrees.   Your fuel gauge will go up too, not as much
> as the water temp gauge, and the oil pressure hardly goes up at all.
>
> And strictly speaking, it's not the headlights that do it; the gauges jump
> when you move the headlight switch to the first position (interior
> lights/marker lights).
>
> Evidently the cause is inadequate grounding of the gauge lighting circuit.
>  There is a single ground wire circuit which runs daisy-chained from one
> gauge to the next to the next, and then eventually finds its way to the
> single
> ground stud on the back side of the battery ground stud.   Bill Taylor
> suggested that running a second ground wire directly to the chassis might
> sort
> it out.   I have ambitions of doing that to my car shortly.
>
> It should be fairly easy to cut off the connector at the end of the daisy
> chain, then install a new one with two wires attached, and run that second
> ground wire down to the chassis, drill a hole and secure it with an eyelet
> connector.   Making the wire a few inches longer than needed will enable me
> to
> pull the panel forward for servicing etc.
>
> I may even try to do this in the next few weeks; I'll let everybody know
> how it works when I'm done.
>
> Mike
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-- 
Rob DuMoulin
904.476.8744
rob at dumoulins.net



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