[Spridgets] Sprite fan temp switch testing - LONG

[WeslakeMonza1330 at aol.com]

Hi list,
 
Since the list seems quite quiet these days I thought I'd post something  
that might be of interest.  I replaced the 20+ year old aluminium alloy  
radiator in my 69 Sprite a couple of months back with a similar aluminium alloy  
radiator that I'd drilled a hole for and had a weld bung welded to (duh it 
was  supposed to be made with this!) for a radiator temp sensor.  I made  
appropriate wiring modifications including fitting a relay (so as not to draw  
the full fan current across the sensor switch (no such relay exists for the 
 toggle switch!) for the sensor but leaving in place the decades old toggle 
 switch as a manual override.  Having fitted a brand new switch and found 
it  did nothing I tested it in boiling water with a jury-rigged test set up 
and when  it still did nothing I returned it for a replacement.  Fast forward 
to this  evening when I decided rather than sit in front of this PC I'd 
test both  the replacement switch and another one with a different (lower) temp 
switching  range.  Here's the results:
 
 
For the first test I used a  saucepan of water being heated on a domestic 
gas cooker hob with an 88-79 switch  wired to a 9V battery (of unknown 
condition) and a brand new Draper test light,  and proved the switch worked (more 
than can be said for its brand new  predecessor) at about boiling point, 
albeit it seemed to switch off  abruptly.  The second test only  using a 82-68 
sensor was more encouraging with a clear on and slower off  although the on 
point seemed similar 
The 88-79 switch was fitted to  my Sprite and the car run up to temperature 
and with a temperature gauge reading  of 115C the fan had not been switched 
on by the sensor so I used the manual  override switch until the gauge 
reading dropped below 90C.  I then removed the 88-79 switch and  replaced it 
with the 82-68 switch and ran the engine whereupon the fan was  switched by the 
sensor at about 112C and was switched off at about 100C (it may  have been 
98C and thus 14C between on and off as expected). 
With testing finished I  concluded that the coolant temp in the top of the 
rad is probably a lot lower  than the coolant temp in the cyl head (where 
the temp gauge sensor is  fitted).  It might have been an idea  to have fitted 
the sensor lower down in the rad.  It’s possible both sensors switch on at  
a temp much higher than their design states, based on my boiling in a 
saucepan  test and practical testing.  Not  least I’ll be buying a switch with an 
even lower switching range. 
Finally - I know my STACK water  temp gauge will also switch the fan (and I 
have a spare relay for that purpose)  but I wanted to get the temp sensor 
working first. 
Final, finally - anyone know of  a solurce to buy a neat Aluminium alloy 
M22x1.5 rad plug because the nylon ones  are rubbish and I don't want a steel 
or brass one. 
Regards 
Daniel 
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