Ect Sensor Grounding

[golf4283]

I have a quick question. Does the ECT sensor need to be grounded? The original installation is on the heater pipes which are metal and provide a ground via the ECT sensor itself.

On my setup I'm running rubber hoses and using a brass "T" fitting and plugging the sensor into the T and passing the coolant on to the heater box. (This is on my '65 Mustang). This setup invariably leaves the Brass fitting on its own and it is not grounded.

My questions is should I ground the brass "T" fitting to the engine? Or will the sensor function properly even if it is not grounded.

 

[f8tlfiveo]

It needs grounded. It will not work without a ground

 

[golf4283]

Awesome! Thanks. That must be why I'm running rich/having hard warm start issues. I'll ground the guage. It appears Brass isn't as conductive so I'll make sure to ground the gauge itself rather than the T fitting.

Thanks!

 

[95Vert383AOD]

On a side note your computer relies on the readings this sensor gives. I have heard of it screwing the computers calculations up by even changing its location on the intake. Ideally you would want this to be as close to the thermostat as possible. But before the thermostat. There is a reason the stock location is where it is. I have used a laser thermometer and you would be surprised at the temp difference between the location its supposed to be and anywhere else. around the intake.

I'm just trying to help you avoid and computer issues when everything is together. It would suck to have your car in closed loop because the sensor never reaches the correct temp.

BTW Closed Loop = Running rich.

 

[golf4283]

Yea it's definitely running rich right now. Just fired it up for the first time yesterday and set the timing/idle. The sensor is located approximately 1" further along the heater supply line than the stock location so that shouldn't be an issue IMO. the thing is it's currently not grounded so I don't think it's getting any signal period. hence my really gassy smelling exhaust.

 

[95Vert383AOD]

Well see if grounding fixes it. But the sensor in the rubber tube and in the manifold could be as much as a 10 degree difference. say you re programmed for 190 and run a 180 thermostat and the sensor sees 160-170. This may or may not be the case. But if grounding doesn't work you know where to look. I would love to see how you modified the coolant lines because i wanted to do something different and remove my coolant tube as the height of my 351 isnt ideal for the stock hoses.

 

[golf4283]

I'll snap some pictures. Honestly though it's a pretty basic solution. And before I post a couple pictures I'll say that 1" was wishful thinking. It's probably about 2-3" down the line. I can get it closer though by modifying my setup. I just did it the way I did for ease of installation. I'll get pictures later.

 

[jrichker]

So far almost all the advice you have gotten is incorrect. The ECT grounds through the black/white signal ground for the computer. The same black/white wire wire is signal ground for all the sensors except the MAF and O2 sensors. The signal ground circuit is the same on both Speed Density and Mass Air Flow cars

The ECT sensor has absolutely nothing to do with the temperature gauge. They are different animals. The ECT sensor is normally located it the passenger side front of the engine in the water feed tubes for the heater.

Here's the wiring diagram...

Diagram courtesy of Tmoss & Stang&2birds

The ACT & ECT have the same thermistor, so the table values are the same

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Note that that if the outside air temp is below 50 degrees F that the test for the ECT can be in error. Warm the engine up until you get good hot air from the heater and then dump the codes again.
Voltages may be measured across the ECT/ACT by probing the connector from the rear. A pair of safety pins may be helpful in doing this. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.

50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

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[f8tlfiveo]

sorry, i was thinking it was a 1 wire sensor like the one for the gauge.

 

[95Vert383AOD]

Oh yeah thats right it is a 2 wire sensor. Doesn't need a ground.

I plan on buying a infrared thermometer after another mechanic at the shop i work at showed me how great they are. Run the car at temp and point it at the thermostat housing and see what temp its running and then point it to the metal part of your sensor and see how hot its getting. The thing is awesome for troubleshooting coolant problems.

 

[from6to8]

On a side note your computer relies on the readings this sensor gives. I have heard of it screwing the computers calculations up by even changing its location on the intake. Ideally you would want this to be as close to the thermostat as possible. But before the thermostat. There is a reason the stock location is where it is. I have used a laser thermometer and you would be surprised at the temp difference between the location its supposed to be and anywhere else. around the intake.

I'm just trying to help you avoid and computer issues when everything is together. It would suck to have your car in closed loop because the sensor never reaches the correct temp.

BTW Closed Loop = Running rich.

what's up man I know this is an old post but my issues brought me to this thread. Btw I talked to you on the groups years ago when I was inquiring about doing a 351. Well here's my issue now with my 94 Cobra; ( from another thread)

My issue is my fan is turning on when I start the car and I've tried a few different used Ect sensors, a few used Ccrm's, and another used Pcm ( all of my parts actually). I did a koeo and got code 511 EEC processor Rom test failed, 117 Ect sensor circuit grounded, and 564 which google seems to say something about fuses or something from what I've read others asking questions about that code which isn't in my chilton's manual.

With the koer test i got a code 998 hard fault present and also the 117 again. There was another code started but didn't get to get the numbers cause the CEL stayed on and the car almost cut off. I switched it off after about a minute or so and waiting 30 seconds to do the test again. I got the same codes and upon the 3rd code starting the car cut off. I repeated that process one more time and the same outcome.

I ohmed the Ect sensor unplugged and got 27.6, 29.8, and 31.6 ( new one from autozone). I didn't buy the one from autozone but wanted to ohm it out to see if the numbers from my old ones compared to it.