coolant temp sensor reading -74?

[50trimgst]

I have a 93 eclipse gsx with a starting problem. i know the problem lies with the coolant temp sensor but not sure why. When i purchased the car i was told the coolant temp sensor pigtale was cut off the car and not by the owner, who is a very good tuner as well as a great friend. so the car ran fine for a week then it started just turning over and not starting. no big deal my plan is to build the car as i have a ton of parts for it. so i just starting ripping stuff out and ordered v3 link full for it. when i took the radiator out i noticed that the sensor for the fans is close to the coolant temp sensor one so i cut it off and wired it in which seems simple since the wires are close to the same color. waited till today when i got link and go to start it and still no start and the coolant temp sensor stilll reads -74 degrees. is there something im missing here? also changed the temp sensor. also there is no provision in my half rad for the fan switch. do i need this sensor to start the car. i have a way for the fans to work another way.

 

[MY1GDSM]

Check for continuity from the sensor wiring to ECU with a Multimeter.

 

[50trimgst]

good idea ill have to go buy one. what settings and readings am i looking for off a coolant temp harness

 

[MY1GDSM]

Your checking for Continuity as a I said... . Continuity is An unbroken electrical path in an electronic circuit.

Skip to 3.40 seconds in this video pretty simple... . Youtube

 

[50trimgst]

Checked it out and it maxes out my analog volt meter. Is that a good sign

Any ideas as what i should do next?

 

[50trimgst]

Is there anything wrong with using the fan switch harness on the bottom of the rad for coolant temp harness.

 

[delta448]

seems simple since the wires are close to the same color

I think your logic may be flawed.

Checked it out and it maxes out my analog volt meter. Is that a good sign

You mean infinite resistance? Between what points?

Any ideas as what i should do next?

If you're measuring resistance between the sensor plug and the ECU, then next you need to fix the broken wire.

Is there anything wrong with using the fan switch harness on the bottom of the rad for coolant temp harness.

Not sure I follow this. You want to use a temp switch in place of a temp sensor? How's that going to work?

The reason the coolant temp is registering at -74 is because there is no continuity between the temp sensor and the ECU. The sensor varies resistance based on the temperature, it has a high resistance at low temperature and lower resistance at high temperature.

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[50trimgst]

Im just using the wires. I cut them off and the connector plugged into the sensor.

 

[93TSI_370K]

I was trying to find what I had written somewhere on my laptop about this for a friend, but I'll have to rely on my memory.

The "thermal" switch on the bottom of the radiator, closes at a specific temperature and opens at another temperature. It is just a switch, albeit one that opens and closes at a specific temperatures, hence it is a "thermal" switch. The switch contacts cannot handle the current flow of the radiator fan motor so it controls a relay coil which has contacts that can handle the load.

There are two temperature sensors in the area of the thermostat housing, and another "thermal" switch if the car has AC. One of the temperature sensors is for the stock temperature gauge, the other is for the ECU. The "thermal" AC switch is to turn off the AC if the coolant temp gets too high.

So switches have two states, on or off.

Sensors are supplied a voltage and the temperature determines the voltage output.

Ditto what delta448 said, I don't know how you are going to do this....

 

[50trimgst]

I had to cut the wires and connector off the fan switch and then used it as a pigtale. As some one cut the original coolant temp sensor harness off my car for whatever reason idk.

 

[50trimgst]

Problem solved bottom coolant temp sensor went bad and my wiring idea worked. Ill take a pic if it helps.

 

[ohyeah]

yes could you take pics please i would like to see this because my sensors on my thermostat housing are all screwed up ( well the wiring i mean) a long with my fan

 

[1gAWD92]

im having the same problem in my 92 RS AWD. please get a pic ASAP. im sick of this problem!

 

[Tsitalon]

There are two temperature sensors in the area of the thermostat housing, and another "thermal" switch if the car has AC.

One of the temperature sensors is for the stock temperature gauge, the other is for the ECU. The "thermal" AC switch is to turn off the AC if the coolant temp gets too high.

So switches have two states, on or off. Sensors are supplied a voltage and the temperature determines the voltage output.

Do you have part number for the AC switch for high temp? This is causing my compressor to not turn on since it is closing at mid range of temp gauge; should be closed sooner then open if temp of coolant goes too high. Seems I have wrong switch; it acts more like a fan switch and probably is.

I think your logic may be flawed.

You mean infinite resistance? Between what points?

Can't use a temp switch in place of a temp sensor. A temp sensor is a varying resistance to vary voltage. A switch is either 0 ohms(on) or infinity ohms (open), no resistance. Not interchangeable and placing temp switch in place of temp sensor is very bad for engine!