Bob,
How can I thank you for that description of the temperature gauge workings?
I am an electrical engineer with years, verily toooo many years of experience
and it dumbfounded me when I installed a temperture gauge in my 4/4. Now I
understand why I did not understand. I was thinking a resistor that varied
with temperature and a milliameter type gauge. What a simpleton i was, when
it can be done with so much more complexity. Works well though.
Richard Cooperman
'69 4/4 with a now understood temp gauge
> From: Bob Nogueira [SMTP:nogera@prodigy.net]
> Sent: Monday, August 23, 1999 8:41 PM
> To: DGreimel@aol.com; Marquis, Gary; aMORGANS@autox.team.net
> Subject: Re:Tech Temp gauge
>
> -- [ From: Bob Nogueira * EMC.Ver #3.1a ] --
>
> The Plus four gauge is somewhat unique in that when off, the needle sits
> on
> HOT and once tuned on moves to Cold. ( see below for the reason ) So if
> the needle is not moving at all try just grounding wire to the sending
> unit for a few seconds and see if the needle moves if not the gauge is the
> problem, if it does move the sender is the problem.
> Note Check: to see if your radiator is grounded . If you are using the
> mounts that look like mini motor mounts and you don't have the rods from
> the radiator to the tool box then there's no ground to the radiator
>
> The resistance value won't help. Inside the sending unit is a bimetallic
> bar wrapped in nichrome wire and the end of the bimetallic bar is a set of
> contact points.
> When the current is turned on the gauge needle moves because it too is
> attached to a bimetallic bar rapped in nichrome wire .As the wire heats up
> the bar bends moving the needle. Since the ground is the sending unit, as
> the needle is moving the bimetallic bar in the sending unit also heats
> up
> until the bar opens the contact points on the end and there is no ground
> so
> both bars start cooling until the sending unit bar again closes the points
> and the current starts flowing again.
> Or Simply put the sending unit is a on off switch and the longer its
> off
> the hotter the gauge reads.
>
> Bob Nogueira
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