Darrell, My car has the "approximate" type gauge. It is the original gauge
that came with the car when I bought the car in 1969. It shows the hot zone
only as a red mark. I've been in the red zone while in traffic and it's not
something I've enjoyed. The car is Commission # 69150L. I can't comment on
what's correct for your car although the Factory Spares Manual I have shows
your style gauge and lists convex glass as the replacement glass, I am
reasonable sure that the convex glass went away with the early 4's. So it goes
for the arguments about originality and the records to support "facts"!
I've done some profiling of the temperature vs. the needle location to
determine the spot that is 180 to 190 and on mine it's just above the center
of travel. The sending unit has a lot to do with the location of the needle
too. I have two sending units and by switching them I can move the needle
about 1/8 inch on the gauge. I profiled the gauge by using an accurate
thermometer and measuring the water temperature at various positions on the
gauge, making a mental note of the operating range where the car seems to run
the best.
While it would be interesting to know what the water temperature is at the
outlet of the radiator, my preference is to know what the water temperature is
at the hottest point in the engine, after all that is what the manufactures
measure and the reason for me placing the probe at the top of the radiator.
Another way to look at it would be this. What if the fan belt broke or for
some reason the water pump was not circulating water. The engine would quickly
begin to overheat but the temperature at the bottom of the radiator may not
change for quite awhile since that water would be cooled but not being
circulated into the engine. The fan probe located at the bottom of the
radiator would show things to be OK while they clearly are not and the
radiator fan would not be coming on. The temperature gauge would show a
problem since it's measuring the temperature at the engine water outlet. While
I do look at the temperature gauge on a frequent basis, the red light that is
wired into the circuit showing that the fan has come on makes me look at the
gauge and continue to monitor the gauge until the light goes off.
These are my arguments for measuring at the top of the radiator.
"That's my story and I'm sticking too it". :-)
JVV
----- Original Message -----
From: Darrell Walker
To: Gerald Van Vlack
Cc: tr list
Sent: Saturday, April 05, 2003 11:23 AM
Subject: Re: Electric Fan Control
On Saturday, April 5, 2003, at 07:16 AM, Gerald Van Vlack wrote:
Darrell, In my opinion at idle you risk having temperatures in the head
reach unacceptable numbers before your fan is activated, even with the lower
settings as you've indicated. I find that my car runs best at 180 to 190 water
temperature. I am able to maintain that temperature even at idle if the fan
turns on soon enough. If allowed to get too hot it takes an inordinate amount
of time to cool. My engine is warmed up a bit with larger pistons, a milled
head and cam so I am generating more heat too.
What does your temperature gauge read at the time when the fan is
activated?
JVV
The fan comes on just before the gauge hits the upper range of the bracket
around the center 70 C mark. Normally the gauge reads just below the 70 C
mark.
As a side note, my car has a temp gauge in C. Is that correct for a 66
TR4A?
Some quick (approximate) conversions:
70 C = 160 F
80 C = 175 F
90 C = 195 F
So I'm guessing that my temp never gets above 80-85 C (175-185 F).
--
Darrell Walker
66 TR4A IRS CTC67956L
Vancouver, WA, USA
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