> -----Original Message-----
> From: Atwell Haines [SMTP:carbuff@scooter.net]
> Sent: Wednesday, March 04, 1998 6:35 PM
> To: triumphs@autox.team.net
> Subject: Spitfire Temp gauge (repeat)
>
> The Temperature gauge on my '79 Spitfire suddenly quit working. (Kind
> of
> like me at 5 o'clock!) The needle doesn't budge.
>
> The gas gauge works OK. I am getting the pulsed voltage at the sender
> unit
> lead (measured with my digital multimeter), about one pulse every
> second.
>
> Resistance at the sender is varying with temp, from 33K ohms hot to
> 147K cold.
>
> 1. Are these sender readings OK? Could anybody check theirs as a
> comparison?
>
> 2. If I short the sender lead to ground, will I hurt anything? [I
> don't
> want to ruin my voltage stabilizer or gauge.]
>
Atwell,
Can't speak about the Spit but here is what I have found (so far) on my
TR6. (I am attempting to diagnose what I believe to be a "compressed"
range of my temp gauge - it only reads up to 1/4 at normal operating
conditions). This info is based on some tips I received from Dan Masters
after inquiring about temp gauge testing earlier last year. I connected
the following resistance values to my temp gauge with the following
results:
200 ohm - 1/4
100 ohm - a little over 1/2
50 ohm - all the way hot
The connection was made by running a lead from the battery + to the
resistor, and then to the wire attached to the sender (I pulled the wire
from the sender). I have not had a chance to test my sender yet but will
do so soon.
Two observations on your findings:
1. The general trend is consistent with mine, ie. lower resistance means
hotter temp.
2. The range of values seems quite high (my values were ohms not Kohms).
Maybe your sender is fried? Or maybe there is something in the wiring
that I am missing which would affect the Kohm values and these values
really are correct.
In any event I would try the gauge test with the resistors. (You might
already know this, but you can achieve the test with two 100 ohm
resistors connected in parallel for 50 ohms and in series for 200 ohms.
I used 1 watt resistors and they were fine - no overheating). At least
this would prove if your gauge (or the wiring to it) is potentially at
fault.
PS. Why would the sender have a pulse? I though it was just a simple
variable resistor (actually a thermistor).
Good luck,
Peter Zaborski
76 TR6 (CF58310 UO)
Calgary AB Canada
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