Date:         Tue, 6 Jul 2010 17:45:06 -0700
Reply-To:     mark drillock <mdrillock@COX.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         mark drillock <mdrillock@COX.NET>
Subject:      Re: adding resister to center 1.9 coolant temp gauge?
Comments: To: Paul Guzyk <paullist08@GUZYK.COM>
In-Reply-To:  <201007061957.AA7930348@mail.interslice.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Be careful. Adding a resistor to "normalize" the reading has pitfalls.
I'm curious why you presume that the sender that in your words died was
reading correctly until then. In any case, a 10 ohm resistor would be
what I would try if I simply had to. Much more than that will prevent
the temp warning light from working right. If I were you I would test
the gauge and gauge wiring with some various resistor values first to
determine if the sender is the problem with the high reading. Here is
what I have come to expect.

33 ohms  = HOT!!! and FLASHING led
50 ohms  = hot but not flashing
67 ohms  = just above the led
100 ohms  = at or just below the led
200 ohms = above cold

Buy a 5 pack of 100 ohm 1/4W resistors from RadioShack for about $1.
Combine them in various ways to get each of the above values.

3 in parallel = 33 ohms
2 in parallel = 50 ohms
1 in parallel with 2 in series = 67 ohms
1 by itself  = 100 ohms
2 in series  = 200 ohms


Mark

Paul Guzyk wrote:
> My 1.9 style dash coolant temp sender died.
>
> I replaced it with a new one.   Now the gauge reads high, about 65%-70% when normal operating temperature instead of 50% (LED dead center) like the old one.
>
> I'm thinking of adding a resister in series with the new temp sensor to get the needle back in the middle.
>
> Anyone seen this before?
> What value resister/pot did you add?
>