Mechanics

RESISTANCE OF GOOD COOLANT TEMP GAUGE SENDIN

1986 Mazda 323

Engine Cooling problem
1986 Mazda 323 4 cyl Front Wheel Drive Manual 317, xx miles

Tried putting a cooking thermometer into the top of radiator with engine running. When meat thermometer read 200 degree F, the inside (instrument panel or dash) analog meter had barely moved off totally cold. Have in hand a Haynes manual for the 1990-2000 323 & Protege. Of course, this is the wrong year. I think that the sending unit may have been damaged due to overheating it.
Parts sellers' description don't list the resistance value of their new units.
Like to know what its ohms are when, let's say, 60, 160 & 200 degrees Farhenheit before I buy a new sending unit.
I think that this meter may be just for driver info & THIS sending unit does not interface with the engine computer or " ECU"?
That is, does the sending unit just directly feed that water temp inside gauge?

Thanks
Avatar
Likntikn
December 31, 2009.



Which component are you working on-Is it the coolant temperature sensor or the engine temperature gauge sending unit? If its the CTS go here:

http://www.2carpros.com/topics/cooling-system/coolant-temperature-sensor--2

Rasmataz
Dec 31, 2009.
Am presently working on the sending unit for the dash mounted analog water temperature gauge.

I am hoping that if I get to a place where I have a more accurately reading one that that will help me to see if the radiator mounted electric fan is coming on late or intermittently.

The usual parts sellers show a 3 parts that have the designation of ~ " cooling" or " coolant" with words like " sensor" or " switch".

But the one electric wire off the top of the thermostat housing has a single flat male blade or spade lug. (( 3 different parts places show a single connector with a sort of rounded " pin" that has a sloped portion at the end.))
Also is a single flat blade located at the driver's side end, not so far from the top of the engine block & is on the side of the engine block facing the radiator that has a single mating wire for it.

I think there is another sensor that is in the real top suface of the engine that has 2 side by side flat blades that is for the ECU.
I measured its ohms at 130 & 160 degree F & it stayed at 41 ohms. Since I think that this is the sensor that feeds analog temp info to the ECU, I think that it must be defective

But am thinking that the sensor that interfaces with the dash mounted water temperture gauge is for the driver's use only & does not interface with the electronics of the engine control system.

The exact function of the water temp sensor (2 prongs - not flat) in the bottom, driver side of the radiator has various answers depending on various sources. It seems to be involved with turning the radiator's electric fan on - but some say it works in conjunction with the single wire sensor mounted on top of the thermostat housing.
I measured the 2 prongs ohms after the car had cooled for a while & it was same as when warmer, namely, zero ohms (but the fan was not on at either water temperature).
Also I get varied info as to exactly what temperature the fan is supposed to start operation.
(this car is " basic" - no air conditioning, etc.)
If the thermostat is supposed to be 180 or 192, then one would think that the fan should come on not too great of a temperture above that but of course if its control is via the 2 prong sensor in the bottom of the radiator, then the sensed temperature will be? 5 or 10? Degress lower than at the top ( hmmm - unless the fan is not running - interesting. )
I can't use a thermometer stuck into flowing water the top of the radiator cause then the water may boil at a little over 212? (With the cap off = no system pressure). I don't think that just " pressing" a meat thermometer against the fins of the radiator will give accuracy.

Also I don't know what the " too high" mark on the analog dash gauge is in degress - it's not marked in any numbers. So I don't know what temperture is by which, certainly, the radiator fan should have come on already.
Thanks

Tiny
Likntikn
Jan 10, 2010.
Its called the coolant temperature sensor/switch the computer uses its input signal for other purposes-such as fuel delivery, the engine temperature sensor at the radiator is the gauge sender and activates the cooling fan and gives the reading at the gauge

Rasmataz
Jan 10, 2010.