Date:         Fri, 22 Jul 2005 08:27:42 -0700
Reply-To:     Keith Hughes <keithahughes@QWEST.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Keith Hughes <keithahughes@QWEST.NET>
Subject:      How's this idea for diagnosing overheating?
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

>Date:    Fri, 22 Jul 2005 03:31:31 -0500
>From:    Max Wellhouse <maxjoyce@IPA.NET>
>Subject: How's this idea for diagnosing overheating?
>
><snip>
>2.This all leads up to the master plan.  That is to take my existing
>water temp VDO cockpit gauge and set up 4(or however many) separate
>senders throughout the cooling system and have a multi position
>switch  that would allow me to read the coolant temp, WHILE DRIVING,
>at the various points along the way and use that info for the diagnosis.
>
>

Keep in mind that the vast majority of these temp sensors are
thermistors - semiconductor devices with an inverse resistivity curve
(i.e. the resistance drops, logarithmically, as temperature increases)
so you're reading on the low resistance end of the scale when you're
operating at temperature.  Thus any contact resistance in the switch
will affect the reading - you'll need a good (i.e. $$$) switch.

>First off, how may would be needed and where would you place
>them?  I,m thinking one before and after thermostat and one sender
>for the inlet and one sender for the outlet hose up by the
>radiator.   Wiring would be the least of my worries, and besides,if I
>get problem number one solved, we might get a decent accounting of
>where the factory needle gauge is reading.
>
>

Upstream of t-stat, radiator inlet and radiator outlet is all you need.
There's no significant cooling between the t-stat and the radiator, so
an additional probe is not necessary.


Keith Hughes