ECT possibly faulty

95strokerPSU

Member

Jul 29, 2004

986

1

19

Sacramento from Philly

Jun 26, 2006

#1

• Jun 26, 2006

• #1

I've been researching what could cause I car to be down on power once it's warm and found a thread that gave acceptable volt and ohm ranges for both the IAT and ECT.

My IAT tested fine, but the ECT with the key on engine off I probed the back of the harness with the sensor connected and only got 2.75 volts. I heard it should be closer to 5 volts. Can anyone tell me what this means (ie: bad sensor?)?

Thanks
Dave

 

95strokerPSU

Member

Jul 29, 2004

986

1

19

Sacramento from Philly

Jun 26, 2006

#2

• Jun 26, 2006

• #2

I just got back home from work and took another reading. With the key on engine off the ECT read about 2.9 volts at the back of the harness plugged in.

Then I unplugged it, and the voltage at the harness went up to about 4.5v. Does this mean my ECT is shot?

I measured the ohms a couple days ago and with an outside temp at 82* my meter read 10,250.

 

95strokerPSU

Member

Jul 29, 2004

986

1

19

Sacramento from Philly

Jun 26, 2006

#3

• Jun 26, 2006

• #3

OK, just did a little research and it makes sense that with the harness unplugged it was at 5v and with it plugged in it was at 3v. The ECT is a resistor so with it plugged in the voltage dropped. But it works against Ohm's Law. So less resistance = less voltage. I don't know how that's possible but I really could care less. Voltage looks fine.

But going back to what I said about the ohm reading I took at 82*F outside temp. My meter showed 10.25k ohms. Now take a look at this chart....



According to the chart, 10.25k ohms is the equivilant of more than 122*F, meaning that if my reading on the ohms was right, that it's off by more than 33%. Does anyone think this could be a warm power loss problem?

 

Attachments

• test.gif

  19.9 KB · Views: 853

BlueOvalStangGT

Active Member

Oct 27, 2003

2,849

0

46

Tampa Florida....USF!!!

Jun 26, 2006

#4

• Jun 26, 2006

• #4

Subscribing, my car pulls timing because my EEC is getting readings and thinks my car is running at 220+*. Let us know what you find and ill let you know if I find mine out.

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

34

129

Jun 27, 2006

#5

• Jun 27, 2006

• #5

The ECT and IAT use thermistors - that's the reason for defying Ohm's Law.

 

95strokerPSU

Member

Jul 29, 2004

986

1

19

Sacramento from Philly

Jun 27, 2006

#6

• Jun 27, 2006

• #6

Does anyone think that based on my reading of 10.25k ohms at 82*F that I should buy another ECT?

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

34

129

Jun 27, 2006

#7

• Jun 27, 2006

• #7

You'd test the sensor with it plugged in as it is in driving.

A quick and dirty calibration test is to see if the low speed fan comes on at ~208*F. If so, the ECT is calibrated decently at that temperature at least. I'm not sure how the testing was done otherwise to comment. ECT's are fairly cheap if one has doubts.

One more thing: do we know that 94-95 ECT and IAT values look like fox values? That chart is about spot-on for fox values.

Good luck.