[xj] Temperature measurements

XJ
1

A little while ago several listers kindly helped with advice and
comments about temperature senders and I promised to let the list
know about the results of some calibration tests.

In the hope that some may find this of use, here are the figures
for an old sender and a brand new one. I’ve also checked what
resistances are required to produce indications on the SII temp
gauge. This has no figures, just the word ‘normal’ on the gauge.

The senders are identical in appearance, the new one is labelled
DAC2583

All temperatures are in degrees C and were measured with the
thermocouple of a digital multi meter while the resistance in ohms
were obtained from a second meter connected across the sensor which
was immersed in a pan of water. The resistance readings were
obtained by substituting a potentiometer for the temp sender,
adjusting it to give a steady reading on the gauge and then
measuring the resistance.

  Old sensor       New Sensor

55� 270ohms 255ohms
60� 230ohms 210ohms
65� 195 177
70� 163 150
75� 145 128
80� 129 110
85� 111 92
90� 90 73
95� 78 62
100� 64 55

Gauge
n o r m a l
^ ^ ^ ^ ^ ^
93 83 73 63 54 45 ohms

(If your browser doesn’t print the columns in a sensible format and
you are interested, email me off list and I’ll send a excel
spreadsheet and image of the dial)

From these figures it seems that a reading in the middle of the
word ‘normal’ could indicate a temp anywhere bewteen 90 and 98 C.
This strikes me as a little high but I’d be interested to hear what
others think.–
al mclean '93 XJS '79 XJ6
Telford, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

// please trim quoted text to context only

2

In reply to a message from almcl sent Mon 6 Dec 2004:

A few years ago a hot temperature was considered a good thing. I
remember many of the car magazines of 20 - 30 years ago
recommending the fitment of an 88 - 90 degree C thermostat ‘as
engines run best at these temperatures’ Fitting thes t’stats
usually meant the engine ran somewhere between 95 - 100 degrees.
With todays thinking & pollution control it seems that the engine
produces too much NOX at these temps. & a cooler running temp is
now the fashion. These temperatures will no harm the engine modern
oils will cope with temperatures of 110 degrees continuously
without deterioration.–
The original message included these comments:

From these figures it seems that a reading in the middle of the
word ‘normal’ could indicate a temp anywhere bewteen 90 and 98 C.
This strikes me as a little high but I’d be interested to hear what
others think.

–
Keith Turner '79 XJ6 based Aristocat, , '81 3.4 XJ6
Swansea, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

// please trim quoted text to context only

3

In reply to a message from Keith Turner sent Mon 6 Dec 2004:

And of course because the system is pressurised and not running
pure water, the boiling point is well above 100C so temps in the
mid-high 90s are not risky. Higher temps are certainly more fuel
efficient within reason but I don’t know about other pollutants.–
Peter Crespin 94 X300 Daimler / 66 2+2 ‘E’
Buxton, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: http://www.jag-lovers.org/lists/search.html

To remove yourself from this list, go to http://www.jag-lovers.org/cgi-bin/majordomo.

// please trim quoted text to context only

4

If you are using Outlook Express 6, change to fixed width format by:

VIEW
TEXT SIZE
FIXED

Gene McGough----- Original Message -----
From: “almcl” almclean@amclean8.fsnet.co.uk

. . .
All temperatures are in degrees C and were measured with the
thermocouple of a digital multi meter while the resistance in ohms
were obtained from a second meter connected across the sensor which
was immersed in a pan of water. The resistance readings were
obtained by substituting a potentiometer for the temp sender,
adjusting it to give a steady reading on the gauge and then
measuring the resistance.

  Old sensor       New Sensor

550 270ohms 255ohms
600 230ohms 210ohms
650 195 177
700 163 150
750 145 128
800 129 110
850 111 92
900 90 73
950 78 62
1000 64 55

Gauge
n o r m a l
^ ^ ^ ^ ^ ^
93 83 73 63 54 45 ohms

(If your browser doesn’t print the columns in a sensible format and
you are interested, email me off list and I’ll send a excel
spreadsheet and image of the dial)

From these figures it seems that a reading in the middle of the
word ‘normal’ could indicate a temp anywhere bewteen 90 and 98 C.
This strikes me as a little high but I’d be interested to hear what
others think.

al mclean '93 XJS '79 XJ6
Telford, United Kingdom

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

// please trim quoted text to context only

5

almcl wrote:

A little while ago several listers kindly helped with advice and
comments about temperature senders and I promised to let the list
know about the results of some calibration tests.

In the hope that some may find this of use, here are the figures
for an old sender and a brand new one. I’ve also checked what
resistances are required to produce indications on the SII temp
gauge. This has no figures, just the word ‘normal’ on the gauge.

The senders are identical in appearance, the new one is labelled
DAC2583

All temperatures are in degrees C and were measured with the
thermocouple of a digital multi meter while the resistance in ohms
were obtained from a second meter connected across the sensor which
was immersed in a pan of water. The resistance readings were
obtained by substituting a potentiometer for the temp sender,
adjusting it to give a steady reading on the gauge and then
measuring the resistance.

 Old sensor       New Sensor

55� 270ohms 255ohms
60� 230ohms 210ohms
65� 195 177
70� 163 150
75� 145 128
80� 129 110
85� 111 92
90� 90 73
95� 78 62
100� 64 55

Gauge
n o r m a l
^ ^ ^ ^ ^ ^
93 83 73 63 54 45 ohms

(If your browser doesn’t print the columns in a sensible format and
you are interested, email me off list and I’ll send a excel
spreadsheet and image of the dial)

From these figures it seems that a reading in the middle of the
word ‘normal’ could indicate a temp anywhere bewteen 90 and 98 C.
This strikes me as a little high but I’d be interested to hear what
others think.

Most interesting and helpful, Al…!

Some additional comments; in previous dealings with the temp transmitter
it was pointed out (Doug - I think…?) that the manufacturing
tolerances are - shockingly imprecise! So the differences between two
presumeably identical items are easily explained, though it doesn’t
necessarily preclude one faulty transmitter. The “new” ones gradient
seems more “even”…:slight_smile:

While testing the gauges response to various resistances is helpful,
this may also vary between instruments. And as the gauge reacts to the
resitances of the actual transmitter it is still necessary to
“calibrate” the two together. After all; it is coolant temp that decides
the resistance of the temp transmitter - and that is what the gauge is
getting.

With the calibrated slope of the transmitter the engine’s actual
temperature can then be ascertained at any time by simply measuring the
resistance of the temp transmitter. This must basically be transplanted
mentally to the gauge - there is no practical way of actually
calibrating the gauge…

And a clarification; the middle of the word “normal” to me seems to show
some 70C on the table, not 90 - 98C…?

But I do love such facts - beats even ingenious theories any time …:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

// please trim quoted text to context only

6

Very good Al! I’m still looking for a graph I got somewhere for the sender
and will send it if I find it.–
Alex
79xj6L SII (BRG + wires)
86xj6 SIII (Black)
61 Sprite MkII (Red)
Menlo Park, Calif.

almcl wrote:

A little while ago several listers kindly helped with advice and
comments about temperature senders and I promised to let the list
know about the results of some calibration tests.

In the hope that some may find this of use, here are the figures
for an old sender and a brand new one. I’ve also checked what
resistances are required to produce indications on the SII temp
gauge. This has no figures, just the word ‘normal’ on the gauge.

The senders are identical in appearance, the new one is labelled
DAC2583

All temperatures are in degrees C and were measured with the
thermocouple of a digital multi meter while the resistance in ohms
were obtained from a second meter connected across the sensor which
was immersed in a pan of water. The resistance readings were
obtained by substituting a potentiometer for the temp sender,
adjusting it to give a steady reading on the gauge and then
measuring the resistance.

  Old sensor       New Sensor

55� 270ohms 255ohms
60� 230ohms 210ohms
65� 195 177
70� 163 150
75� 145 128
80� 129 110
85� 111 92
90� 90 73
95� 78 62
100� 64 55

Gauge
n o r m a l
^ ^ ^ ^ ^ ^
93 83 73 63 54 45 ohms

(If your browser doesn’t print the columns in a sensible format and
you are interested, email me off list and I’ll send a excel
spreadsheet and image of the dial)

From these figures it seems that a reading in the middle of the
word ‘normal’ could indicate a temp anywhere bewteen 90 and 98 C.
This strikes me as a little high but I’d be interested to hear what
others think.

===================================================
The archives and FAQ will answer many queries on the XJ series…
FAQs: http://www.jag-lovers.org/xjlovers/xjfaq/index.html
Archives: Jag-lovers Forums - Jag-lovers

To remove yourself from this list, go to Jag-lovers Forums - Jag-lovers.

// please trim quoted text to context only