Temperature Gauge not working?

Tiny
JBRYAN328
  • MEMBER
  • 2002 FORD F-150
  • 4.2L
  • V6
  • 2WD
  • AUTOMATIC
  • 107,000 MILES
When my temperature gauge quit working my truck started idling high and starting rough. Then it got to the point of just cranking over and not starting at all unless I hold the gas peddle to the floor and then it will start but real rough with a lot of smoke coming out of the tailpipe. After I get it started and running a little smoother it idles high all of the time. When I get up to speed in town (35 to 45 mph) I can basically take my foot off of the gas peddle and it will run like I have cruise control on (which I do not have) until I apply the brake. I'm on a very fixed income and I would appreciate any help or advice you can give me. PLEASE HELP! Thank you in advance and be blessed : )
Wednesday, June 24th, 2015 AT 7:26 PM

20 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
From the symptoms it sounds like your coolant temp sensor went bad have you had it scanned for codes in the computer yet?
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Wednesday, June 24th, 2015 AT 10:27 PM
Tiny
JBRYAN328
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The check engine light is not coming on at all so I didn't think that it would send any codes out. So, to answer your question. No, I did not. If I change out the coolant temp sensor. Will that fix the temperature gauge so that it will work again as well as fix the rough start and high idle problem?
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Wednesday, June 24th, 2015 AT 11:26 PM
Tiny
SATURNTECH9
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I cant say for sure but with the temp gauge not working and it sounds like its flooding like its getting too much fuel it would make sense. If the wires to the sensor get chewed or damaged or the sensor itself failed. The computer would see the coolant temp lower then it actually is giving the engine too much fuel. Just because the check engine light isnt on doesnt mean that there aren't any codes in the computer.I would check for codes inspect the wiring too it etc. If I had the truck thats what I would do.I would also use a scan tool and see what the coolant temp was reading on the scan tool verus actual temp with a infared temp gun. If your going to work on your vechiles I would invest in a scan tool especially one that read some live engine data they have come down in price a lot.
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Thursday, June 25th, 2015 AT 6:07 AM
Tiny
JBRYAN328
  • MEMBER
  • 3 POSTS
Thank You so much! I will look into this and hopefully resolve my problem. Many Blessings to you and yours : )
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Thursday, June 25th, 2015 AT 1:26 PM
Tiny
SATURNTECH9
  • MECHANIC
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Your welcome glad I could help.
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Thursday, June 25th, 2015 AT 6:42 PM
Tiny
ROBJS111
  • MEMBER
  • 6 POSTS
  • 1998 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 171,000 MILES
Coolant Temp Guage on my 98 f150 2wd 4.6 auto is not working. Checked the sensor, replaced with new one and still nothing. Then checked ohms at sensor and was ok, did not show open circuit.

What volts should I see when checking the opposite end of pigtail that plugs into sensor?

What should I check next?

Getting heat in cabin but truck seems to have a rough idle. Dont think computer is getting correct engine temps.

Ecm sensor 25000 ohms and going down as I take measurements. Gauge sensor 2700 ohm and going down as well. Seems like as I hold sensor in hand ohm go down but if I stand sensor upright ohm stay steady? 25k ohms seems kinds high. What do u think?

Will place sensors in pot of hot water and post findings.

Thanks.
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Friday, January 22nd, 2021 AT 12:25 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
1. Disconnect Sensor - Ensure temperature sensor connector is in good condition. Turn ignition off. Disconnect coolant temperature sensor. Turn ignition off. If temperature gauge indicates does not indicate cold, go to next step. If temperature gauge indicates cold, go to step 3). 2. Check Red/White Wire For Short To Ground - Turn ignition off. Measure resistance of Red/White wire between coolant temperature sender connector and ground. If resistance is more than 10 k/ohms, go to step 4). If resistance is less than 10 k/ohms, repair Red/White wire. Retest system. 3. By-Pass Temperature Sensor - Connect a jumper wire between the 2 pins of temperature sensor harness connector. If temperature gauge indicates hot, replace coolant temperature sensor. If temperature gauge does not indicate hot, go to step 5). 4. Check Red/White Wire For Short To Ground - Turn ignition off. Disconnect instrument cluster harness connector C237. Measure resistance between instrument cluster harness connector C237 pin No. 9 (Red/White wire) and ground. If resistance is more than 10k/ohms, repair/replace instrument cluster. If resistance is less than 10 k/ohms, repair short to ground in Red/White wire. Check gauge operation. 5. Check Red/White Wire & Pink/Orange Wire For Open - Turn ignition off. Disconnect instrument cluster harness connector C237. Measure resistance between C237 pin No. 9 (Red/White wire) and pin No. 5 (Pink/Orange wire). If resistance is less than 5 ohms, repair/replace instrument cluster. If resistance is greater than 5 ohms, repair open Red/White or Pink/Orange wire. Retest system.
Test ECT this way.


https://www.2carpros.com/forum/automotive_pictures/62217_ect_5.jpg

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Friday, January 22nd, 2021 AT 12:25 PM (Merged)
Tiny
ROBJS111
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  • 6 POSTS
There are 2 sensors one black and the other gray. The gray sensor is inboard to the black sensor and both located top pass side intake manifold. Also both sensors on same wiring harness. Sensors look fine, no leaks or corrosion. Checked each sensor with engine on:

black 13.3 v / 670 ohms
gray 4.6 v / 1540 ohms

engine off:

both showing 800 ohms, about.

Installed jumper between the sensor connectors and still gauge showing hot.

Can you tell me what each sensor is, function of?

Also with connectors off and engine on temp gauge still pegged at Hot.

Do I have a short?

Also both have red/white wires. One with red and white stripes the other is white with red stripes.
Edit/Delete Message
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Friday, January 22nd, 2021 AT 12:25 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Temp gauge sender has red/white stripe and yellow/red stripe, yellow/red is the ground red/white is gauge wire. ECT has lt green/red stripe and gray/red stripe.


https://www.2carpros.com/forum/automotive_pictures/62217_sender_1.jpg



https://www.2carpros.com/forum/automotive_pictures/62217_ECT_11.jpg


Check red/white for short to ground.
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Friday, January 22nd, 2021 AT 12:25 PM (Merged)
Tiny
BRIAN K CONNER
  • MEMBER
  • 35 POSTS
  • 1996 FORD F-150
  • 4.9L
  • 6 CYL
  • 2WD
  • MANUAL
  • 172,000 MILES
Just replaced the temperature switch on engine because the gauge on the cluster stopped working. Gauge is still not working. The first one. Now where is the second one located at? It is a 4.9. Help!
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
CJ MEDEVAC
  • MECHANIC
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I can fix you right up! Course you know next time you see me, you owe me lunch!Click on diagram below. The Medic
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
66JETHRO
  • MEMBER
  • 3 POSTS
  • 1995 FORD F-150
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
I have had both sensors replaced and the gauge still doesn't work
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Is the gauge not registering anything or is it just inaccurate?
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
66JETHRO
  • MEMBER
  • 3 POSTS
It is not registering anything. All the other gauges are working in the dash.
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
If the coolant temperature sensor is OK then the gauge itself is faulty. Remove the instrument panel and inspect the circuit board. Sometimes just one circuit can become burnt and you may be able to resolder it together.
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
66JETHRO
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Thanks, I'll try that.
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Friday, January 22nd, 2021 AT 12:26 PM (Merged)
Tiny
NABILALMASRI
  • MEMBER
  • 16 POSTS
  • 1992 FORD F-150
  • 5.2L
  • V8
  • 2WD
  • AUTOMATIC
  • 258,000 MILES
The temperature gauge does not work. The fuses are okay.
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Friday, January 22nd, 2021 AT 12:27 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,271 POSTS
Hello,

Can you turn the key to the on position and then remove the sensor wire and hold it to ground? This should make the gauge go to full hot meaning the sensor is bad.

Here is a guide and some diagrams to help you get the problem fixed:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Check out the diagrams (below).

Please let us know what happens.

Cheers, Ken
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Friday, January 22nd, 2021 AT 12:27 PM (Merged)
Tiny
LUCKY1942S
  • MEMBER
  • 1 POST
  • 1987 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 93,239 MILES
Temperature gauge stopped working (one day it worked next day it didn't.) I pulled the gauge and it worked, checked the print circuit and it seem to be fine. I then replaced the temperature sending unit. The one by the thermostat housing. Don't know where to go from here. Would appreciate any help you can give. Thanks in advance
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Friday, January 22nd, 2021 AT 12:27 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Have someone ground the wire at the sender while you watch the gauge, should go all the way to Hot, if not there may be a problem with the wire between the gauge and the sender.Here is the wiring diagram for your dash


https://www.2carpros.com/forum/automotive_pictures/1639_F150_4.jpg

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Friday, January 22nd, 2021 AT 12:27 PM (Merged)

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