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Old 08-14-2009, 06:46 PM   #1
AlanS
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Default How do I check the ECT sensor? Use of Multi-meter!

My ECT sensor is possibly not working on my 95- 850. In order to get an exchange, I need to PROVE it's bad. I don't want to be embarrassed, so I picked up a multi-meter.
OK...I got a Multimeter. I am electronically ignorant...a moron! The Ohms section has 5 choices: 2000K, 200k, 20k,2000, 200. What do I set it on for testing the ECT sensor? What am looking for? A simple explanation would be helpful...make believe you are talking to a 5 year old...an not a bright one!!!
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Old 08-14-2009, 07:28 PM   #2
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Set the ohmmeter to the 20K range.
Depending on sensor temperature you should get the following results:
COOLANT TEMPERATURE SENSOR RESISTANCE TABLE
Temperature - F ( C) Ohms
32 (0) ...........................7300
68 (20) ........................ 2800
176 (80) .........................300
212 (100) .......................150
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Old 08-16-2009, 06:35 PM   #3
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Quote:
Originally Posted by vlvman View Post
Set the ohmmeter to the 20K range.
Depending on sensor temperature you should get the following results:
COOLANT TEMPERATURE SENSOR RESISTANCE TABLE
Temperature - F ( C) Ohms
32 (0) ...........................7300
68 (20) ........................ 2800
176 (80) .........................300
212 (100) .......................150
OK...so here's what I did:
Engine cold...85 degrees out all day. The meter set at 2000, the reading was 1740, at 20K 1.75....I let it heat up to operating temp (via the interior gauge): at 2000= 225, at 20K .25 This kinda corresponds to your chart, but not exactly. It did go down!
So, if it's not the sensor, then I guess it's the leads going to the sensor...those barrel connections that I can't get inside of to clean. I used a very small jewlers file to try to rough up the inside of the barrel, but the Code still comes up.
Any ideas?
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Old 08-16-2009, 06:41 PM   #4
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Yes, replace the thermostat. The ECU allows a set amount of time for the engine to reach operating temperature, if your stat is sticking partially open it won't reach operating temp in time and will trip a code for the ECT.
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Old 08-16-2009, 06:48 PM   #5
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Quote:
Originally Posted by vlvman View Post
Yes, replace the thermostat. The ECU allows a set amount of time for the engine to reach operating temperature, if your stat is sticking partially open it won't reach operating temp in time and will trip a code for the ECT.
GEEZ, I just replaced the stat when I replaced the sensor. So, you feel that the sensor IS working? Does the Stat have a 'proper' orientation? I saw a small hole in the frame of the thermostat, but just put the darn thing in. BUT, this combo (new stat/ new sensor) worked for about one month.!
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Old 08-16-2009, 06:54 PM   #6
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The hole in the stat is a bleed to prevent air being trapped in cooling system and the hole goes up.
Did you replace the stat with the same temp rating? Was it a Volvo stat or aftermarket stat? Do you suspect wiring as the fault?
Many a new stat are junk.
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Old 08-16-2009, 07:08 PM   #7
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If you feel the fault is the wiring, do the above ECT test at the ECU, you should get the same results at the ECU if the wiring is good. Here you will find the best wiring diagram available to me at the moment.
http://www.volvoclub.org.uk/volvo_wo...techdocs.shtml
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Old 09-01-2019, 02:25 PM   #8
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What are the resistance values for the 2.4/Regina ECT? I’m getting roughly 530 ohms at operating temp

Over 200f and getting 400 ohms
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Old 09-01-2019, 03:12 PM   #9
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Quote:
Originally Posted by iHateVolvoPeople View Post
What are the resistance values for the 2.4/Regina ECT? Iím getting roughly 530 ohms at operating temp

Over 200f and getting 400 ohms
That seems a bit high, but are you measuring correctly?
There are 2 separate resistors in the sensor; 1 for ignition, 1 for fuel.
You measure each pin separately to ground, not to each other.

Here's a chart I borrowed from Autozone...

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Old 09-01-2019, 03:26 PM   #10
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Quote:
Originally Posted by MasterBlaster View Post
That seems a bit high, but are you measuring correctly?
There are 2 separate resistors in the sensor; 1 for ignition, 1 for fuel.
You measure each pin separately to ground, not to each other.

Here's a chart I borrowed from Autozone...

Oops did not know that.
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Old 09-02-2019, 09:45 PM   #11
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Remove the cover from the ECU plug and check there first, if bad readings then check the sensor, should be able to delineate wiring or sensor.
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Old 09-04-2019, 02:32 AM   #12
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Unless yours is a freak of nature...
Ignition box (by steering column) - Pin 2 red/black
Fuel box (behind right kick panel)- Pin 13 grey/white

I've got a piece of paper in the car to remind me (whenever I get ambitious and decide to finally check mine). Might just fix the loooooooong crank before it starts.
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Old 09-04-2019, 10:11 AM   #13
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Quote:
Originally Posted by MasterBlaster View Post
Unless yours is a freak of nature...
Ignition box (by steering column) - Pin 2 red/black
Fuel box (behind right kick panel)- Pin 13 grey/white ...
And if your is the 240 in sig, the ignition cu terminal (at passenger's toes) pin 2 is blue/red
and fuel box (just like in the 7/9) pin 13 is also blue/red if that's not freaky.
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Old 09-04-2019, 10:17 AM   #14
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Quote:
Originally Posted by MasterBlaster View Post
Unless yours is a freak of nature...
Ignition box (by steering column) - Pin 2 red/black
Fuel box (behind right kick panel)- Pin 13 grey/white

I've got a piece of paper in the car to remind me (whenever I get ambitious and decide to finally check mine). Might just fix the loooooooong crank before it starts.
I had an extended crank time when I had a bad fuel pressure regulator. Like a reallllly long crank. It was especially bad when warm since the engine didn’t require as much fuel as it does when cold.
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