ECT diagnosis and high temperatures.

[tracy_s_1993_atx]

Greetings,
My 1993 SHO ATX has been running a little hotter than normal. I installed a manual temperature gauge and the temperatures are as follows:

Engine Idling:
224F -> Fans run at low speed.
218 F-> Fans turn off

Engine Idling A/C running:
Fans run and the temperature stays at 191F with an ambient temperature of 98F.

The Fans do work at high speed when I pull the codes. No codes set!

I purchased a breakout box to try and diagnose the problem.

Battery disconnected and ECU disconnected with breakout box installed
Test Pin 46 to ECT -> 0.0 Ohms
Test Pin 7 to ECT -> 0.0 Ohms

So I know the wiring to the sensor is good.

Now I connected the ECU to the breakout box and ran the engine.
Test Pin 20(case ground) to Test Pin 26(VREF) -> 5.17 volts

Test Pin 20(case ground) to Test Pin 7(ECT) -> 0.618 volts when fans turn on low speed.
Test Pin 20(case ground) to Test Pin 13(Low Fan control) -> 13.7 volts Fan on
Test Pin 20(case ground) to Test Pin 31(High Fan Control) -> 0.0 volts

Test Pin 20(case ground) to Test Pin 7(ECT) -> 0.655 volts when fans turn off.
Test Pin 20(case ground) to Test Pin 13(Low fan control) - > 0.0 volts
Test Pin 20(case ground) to Test Pin 31(High Fan control) -> 0.0 volts

What voltage should I see on Test Pin 46 (Signal Return)?
That Test Pin seems to be shared with many other sensors i.e. O2 Sensors, ECT, Ocatne Adjust, Power Steering Pressure switch, Throttle Position Sensor, Knock Sensor, Intake Air Temp. Sensor an the DPFE sensor(EGR).

I am wondering if the ECT sensor(new) I am using is not properly calibrated for our SHO's?
I have the service manual and I have a chart for temperature vs resistance. And temperature vs voltage.
I will probably pull the ECT and test in a hot *** of water and test the resistance as the temperature changes.

Which ECT sensors are the SHO owners on this forum using? I think that I have the Standard Motor Products TX6. I would like to find a OEM motorcraft ECT, but that does not look to be available.

I tried with a different ECU and CCRM and get the same results.

Suggestions?

Thanks in advance,
Michael

 

[luigisho]

ECT (Engine Coolant Temperature), DY-681 F2AZ-12A648-A

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=F2AZ-12A648-A&_sacat=0

I am seeing this oem part in inventory. Are you looking at another coolant sensor?

 

[tracy_s_1993_atx]

I am looking at local parts stores. I guess that I could just get one from Ebay and check that one as well.

Thanks for the link.

Michael

 

[NoSlo]

Measurements at the sensor. Resistance is with the harness unplugged.



Voltage is the return wire. Pin 7, LG/R at the ECU. The other sensor wire is 5V reference. The voltage reference is used by several sensors, such as TPS, and reference voltage should be 5V. Voltages in the temperature table, +/- 15%.

You can measure with the sensor installed and engine running. Jam a multimeter probe into the back of the sensor connector, and ground the other. If you get 5 volts, it's the other sensor wire. Measure temperature reading of the outlet housings and compare.

From my "cooling fan rebuild howto":

Your car's cooling fan, or dual fans, have two speeds. It should turn on low when the car's temperature is measured at 215 F, and should switch to high if it reaches 230F. It will switch back to low or off once these temperatures have been lowered by a few degrees.

With the A/C on, the fan(s) will run continuously, unless the car is going over 45 MPH and the coolant temperature is below 220F.​

The turn-on temperatures and voltage would be better measured with an infrared thermometer pointed at the water outlet housings.

The temperature sensor is standard for almost every Ford for decades.

 

[tracy_s_1993_atx]

I have purchased a few Sensors from the local chain stores:
Duralast SU201
Standard Motor Products TX6
Master-Pro 2-9362
Napa MPE TS4060SB

I tested each with a *** of water slowly heating using two thermometers for temperature readings and my Fluke DVM to check the resistance.
View media item 510
The Napa ECT sensor closely follows the Specifications from the Ford Service Manual.

The Duralast ECT was the worst, followed by the Master Pro, the STD TX6 and then the Napa brand.

I am going to replace my ECT with the sensor from Napa and test again on my SHO. I plan to get a Ford sensor either from Ebay or directly from Ford and then do the stove top testing as well.

I did use an infrared thermometer to validate the manual gauge that I have installed.

 

[NoSlo]

You run out of steam at the boiling point of water...

I was thinking instead you could drill and tap threads into the end of a cast 20lb dumbbell, like I crank out reps on. Perhaps fill the void with oil or straight coolant, and score the tapped threads so liquid pressure can escape. Screw the sensor(s) into the weight. Shield the probe wires from heat. Put the dumbbell on a hot plate, or apply a propane torch to the handle side of the dumbbell weight. There would be plenty of mass to moderate the temperature, and the sensor would measure like it does in the car. Heat up to 240F, and plot the resistance curve as it cools, as you also monitor with an infrared thermometer (or thermocouple on your dual-trace recording instrument).

The table of values indicates that the ECU has an internal voltage divider with a ~20.5 ohm resistor. The tolerance of this resistor and how it is affected by heat will affect the ADC measurement of the sensor resistance, therefore it is best to confirm not just that the sensor resistance is in spec, but confirm the voltage in-car is in spec.

 

[SHOMON]

It looks like the sensor DY-681 has superseded to DY-1145. It has a different connector but comes with the replacement pigtail. $25.79 on RockAuto.

 

[tracy_s_1993_atx]

I ordered the Ford 9U2Z-12A648-A - SENDER ASY and will test and graph the results against the Service manual.

 

[tracy_s_1993_atx]

Well an update. I installed the NAPA ECT and the fans turn on at 215F and off at 210F just like the manual states.

No more garbage sensors from AutoZone(Duralast) or Oriellyauto(Master Pro) for me. From now on it is NAPA brand or OEM. I have been fighting this issue way too long.

Very frustrated

 

[NoSlo]

Could also just be luck of the draw, allowable manufacturing tolerances, unless the parts counter wants to let you test their entire stock for consistency.

 

[tracy_s_1993_atx]

You might laugh, but I have asked the counter person for all of their stock before to be able to compare. I was looking for some Timken bearings that were not made in China. They had a mix of USA, China, Mexico and Poland.