FC3S_nataku

iTrader: (3)

hey everyone, i started my car yesterday and i did not read any temp can someone tell me where the water temp sensor is please so i can fix this. thanks

Gabe

classicauto

iTrader: (3)

the temp sender is in the water pump housing...it has a green plug
its in the upper most throat of the pump....on the back

Aaron Cake

iTrader: (1)

Actually, the gauge sender is located underneath the oil filter. It's a round white connector that likes to get greased up and then make intermittant contact. Pull it off, clean it and reinstall. While you are there, do the same to the oil pressure sender.

The sensor on the back of the water pump housing is for the ECU only.

All of this information is located in the factory service and Haynes manuals.

classicauto

iTrader: (3)

oopsie - thanks for the correction aaron

silverrotor

iTrader: (1)

Awhile there, be sure to thouroughly wipe and remove all grease that has saturated that area of the wires (Including the ones leading to the Tranny). Chances are you will find that the Insulation has cracked on them further countering your readings.

Don't be lazy! Take the time to cut them at the crack of the Insulation, resolder them and slip shrink wrap over your connection. I did this years back and I found my readings (more particularily to the Oil Pressure) more consistent.

FCGTX

Mine snapped off a couple weeks ago when I was doing some maintenance and accidentally rested my hand on it. Should this dramatically effect the way my car runs or performs?

(Sorry to jack )

NZConvertible

Aaron Cake

iTrader: (1)

Yes. The ECU uses this sensor to determine engine temp, and adjusts the A/F ratio accordingly. With the sensor disconnected, the ECU defaults to a temperature of either 60 or 70 degrees, I forget which.

The connector is very similar to connectors on injectors which you can purchase from many automotive parts stores. You may have to file down the little locating ridge on the temp sensor to make the connector fit as it is offset from the standard center ridge. The polarity doesn't matter.

If you broke the sensor instead, it's cheap and easy to replace.

Digi7ech

iTrader: (1)

70 sounds right for the default temperature for a bad/missing sensor.


While your down there check the integrity of the heater hose there.

More common on NA's than TII's due to the Oil fill tube, oil will spill onto this rubber hose.

After a while the rubber gets soft and CAN lead to a rupture which can cuase your engine to opverheat and go boom

HAILERS

80 degrees C or 176 F.

FCGTX

Good to know, thanx. I'll have to run out to the RX-7 graveyard and grab one.

Mint87RX7

that sensor is freekin weird, its a singal wire thermistor that somehow puts out a digital signal... anyone know how that works?

NZConvertible

Thermistors do not put out any signals, let alone digital ones. Their resistance varies with temp and that resistance varies the current in an electrical circuit. In the case of the temp gauge that varying current moves the gauge needle.

Aaron Cake

iTrader: (1)

As NZ said, the temp sensor is a standard metric BOSCH sensor used on my imports. It's resistance varys with temperature. I forget the exact value, but it's in the service manuals. It's a thermister, so you can measure it by setting your meter to kilohms and connecting to the two terminals (with the ECU plug disconnected, of course).

Peyman

iTrader: (2)

so for the car to be able to run correctly, the sensor must be connected to the factory water temp gauge?

So if i was to disconnect the stock water temp gauge and hook it up to an aftermarket gauge, the car would not run as it should?

Sorry for hijacking, i have a tII that needs a h2O sensor, and if it thinks its 70 degrees outside that means its running lean and that means death to engine.....

HAILERS

WATER TEMPERATURE SENSOR........GOES TO THE WATER TEMPERATURE GAUGE. IT HAS NO INPUT TO anyting ELSE.

wATER tHERMO SENSOR..........dEDICATED TO THE ecu ONLY fOR fUel cOnTrOL.

WaTER TEMPERATUR SENSOR AND waterTHermo sensors are TwO SPEeratE items locTed IN TWO DIFFERENT loCAtIoNS.

Mint87RX7

I know what a thermistor is, i was just saying that when I hooked an O-Sope up to it it was putting out a digital signal. I was like what the hell so i made sure it was completely disconnected and hooked it back up to the scope and it was still an output with higher frequeincy the hotter the engine got. Didnt make sense to me or anyone else working on the car with me...

NZConvertible

A thermistor can't generate voltage. I don't know what you were reading but it wasn't coming from the temp sender.

RotaryEvolution

iTrader: (30)

calm down guys, i think Hailers' head is about to pop....

Mombodogs

Sorry for such a lame response from the DOG, but buy a new one! The junkyard is great for picking up parts and switches, not picking up anything electrical that directly relates to the operation of the "rotary masterpiece". The gauges and sensors are all relative to the correct engine operation. Spend the 25 bucks, and be sure. Junkyard is my second home, but not for items important as this.

PEACE THE DOG

RotaryEvolution

iTrader: (30)

whilel i do agree but sometimes these little pieces are a bit more pricey than we think or would like.

Mombodogs

Point noted Karack, but I replaced the coolant temp sensor, coolant level sensor, 0-2 sensor, total cost for all three, less than a hundred bucks! I didn't buy the car , used 1990 FC3C for its competitive part values, and I figure 100 bucks now, might prolong the "ultimate repair". Just my opinion, but get a new one bro. And Karack, a man of your upstanding position in this forum, please tell me your not a tight-wad when it comes to your car, cause your to close to where I live for me to have to come and replace all of your electronics with 'NEW' ones! Your a good man,

PEACE THE DOG

HAILERS

I can't stand people who can't reach over there and touch the caps key. We waterboard those people at work then bury them in sand up to their necks next to a ant hive, pour honey over their heads and set the red ants to work.

Aaron Cake

iTrader: (1)

A thermistor doesn't generate a voltage...Not sure what you were reading with the scope but if you connect a scope directly across the thermistor all you are going to read is a flat line with possibly some slight interference caused by the cable inductance and stray signals. If the car is turned on when you do this and there are wiring problems, the "digital" signal could be due to loose connections. Going from zero volts to some value as the car vibrates could look like a digital signal I guess.

But a higher frequency the hotter the car got? Maybe you were reading interference from somewhere else....Or perhaps the stock ECU uses the thermistor as a resistor in an oscillator circuit for analog to digital conversion...That's more likely as this is commonly done (especially on old ADCs...successive approximation).

Either way, you need to check the sender with an ohmmeter, with the ECU connector unplugged and the car off and at a known temperature.

FC3S_nataku

iTrader: (3)

hey where is the plug on the harness? is it by the injectors? im only asking this because i found one loose pin clip by the oil insert tube but i wont reach the sensor plug