Temperature gauge, reading low? Inaccurate? Fixed - JeepForum.com

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post #1 of 18 Old 04-23-2012, 10:54 PM Thread Starter
hdrocknroll
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1995 ZJ 
 
Join Date: Dec 2011
Location: Flint
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Temperature gauge, reading low? Inaccurate? Fixed

I've seen other people on here with the same problem.
You see in the first picture of the dash, where my temperature gauge has been running for quite a while now. It didn't bother me much because I checked it with my infrared thermometer, and it was actually running about 200.
I decided it was time to fix it right, and deducted that the coolant temperature sending unit was probably the culprit.
The part was a little hard to find, when I looked for temperature sensor I kept Coming up with the sensor that is up by the thermostat,which is the one that feeds the PCM, when I searched at advance auto for temperature switch I found it,go figure!
This is the one I used to replace it with, nine dollars and some change with the discount.
BWD Coolant Temperature Sensor, part number, WT430

Here is A couple more part numbers, Duralast,Auto zone, PN.TU236 Temp Switch.
And, NAPA part No. TS6685

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This is where it has been running all the time when hot.

img_20120421_194213.jpg

This is where it runs now, warmed up, after replacing the sending unit.
A bit more accurate now.

img_20120423_191959.jpg

Here is the old one, as you can see it is cracked, it's a wonder it worked at all.

dsci0317.jpg

Now ! this little bugger is kind of hard to get at, because it is back by the firewall.
Me being 5' 3" I had to literally crawl into the engine compartment, to get at it, . I bet that would've been a good picture
You can see in the illustration below where the, coolant temperature sending unit is located, on my 4.0, and the 5.2
I pulled off the wire holder deal that goes on the valve cover studs, to move back out of the way a little.
I used a stubby ratchet and a 1 inch extension, with a 13 mm deep well socket, to remove the old one, the new one required a 9/16 deep well socket,the one I had to open the hood back up and retrieve.
I cleaned the connector with some contact cleaner,and put a little dialectic grease on the new sensor.
If your gauge is showing your running hot. you probably have a different problem.
If it's running low like mine was this may be your problem.

I hope this helps some people out, especially because, I had this all done, and thought I had submitted it, but didn't,
I closed that window and lost it all,so I had to do it all over again.

temp-send.jpg


Always !! Keep A Firm Grip On Your Tool !!

Watch Out For The Air Hose Gone Wild!! Or Wear A Cup,: True Story


Quote:
Originally Posted by rooster51 View Post
Whats the worse that can happen? Your jeeps already broke.


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post #2 of 18 Old 04-24-2012, 10:29 AM
sebian
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1995 ZJ 
 
Join Date: Sep 2009
Location: Austin
Posts: 1,511
Your pics look eerily familiar! I went through the same issue last summer. 110* ambient temp, sitting in traffic on the highway and my coolant temp was showing 160*. Dropped in a new temp sensor and it is now showing right where yours is sitting.

Good write-up, and thanks for posting it. I imagine that others will find it very useful!

1995 ZJ 5.2L V8 318. 230,000 miles and still rollin.

List of parts not replaced yet:
...
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post #3 of 18 Old 04-24-2012, 10:38 AM
zander21510
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very cool! I might just take a look at mine to see if its gunked up or something...seems to be showing temp fine but it's worth a check. Thanks bud!
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post #4 of 18 Old 04-24-2012, 03:05 PM
edpmedic
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Join Date: Nov 2011
Location: Baldwin
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Now i'm confused I thought the first one would be right. 195 and the second one would be to high. After I replaced my water pump and thermostat. I'm sitting where the first picture shows. Now when my pump went I overheated for less then 3 minutes. Now I wonder if my temp sensor is bad, of that is the proper place it should show. What are each line suppose to represent on the temp have between the numbers? I must be counting wrong.

Never4get those who gave their lives on 09-11-01 WTC and Pentagon. FDNY-EMS-NYPD-PAPD. Also those who are still dying.
_______________________________________________
"Freedom is never voluntarily given by the oppressor; it must be demanded by the oppressed."
Martin Luther King, Jr.
_______________________________________________
"Always aim at complete harmony of thought and word and deed. Always aim at purifying your thoughts and everything will be well."
Mahatma Gandhi
_______________________________________________
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post #5 of 18 Old 04-24-2012, 03:34 PM Thread Starter
hdrocknroll
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Quote:
Originally Posted by edpmedic View Post
Now i'm confused I thought the first one would be right. 195 and the second one would be to high. After I replaced my water pump and thermostat. I'm sitting where the first picture shows. Now when my pump went I overheated for less then 3 minutes. Now I wonder if my temp sensor is bad, of that is the proper place it should show. What are each line suppose to represent on the temp have between the numbers? I must be counting wrong.
Each line on the gauge is 27.5 degrees up to 210, after that it looks like it's about, 12.5 degrees per line.

Always !! Keep A Firm Grip On Your Tool !!

Watch Out For The Air Hose Gone Wild!! Or Wear A Cup,: True Story


Quote:
Originally Posted by rooster51 View Post
Whats the worse that can happen? Your jeeps already broke.


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post #6 of 18 Old 04-24-2012, 04:04 PM
dean477
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1998 ZJ 
 
Join Date: Aug 2010
Location: Los Angeles
Posts: 192
My 4.0 runs exactly where yours does after the new sensor. Occasionaly, my temp gauge stops working and goes to zero mid drive then returns to just below 210.
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post #7 of 18 Old 04-24-2012, 10:23 PM
JohnnyZJ
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i jsut swapped a waterpump/tstat on mine and it seems like it takes forever to get to the first hash mark. i thought something was wrong too. i'm gonna swap the sensor to. i was thinking it already, then ran across this post.

i run in the exact same spot on my 5.2. i thought originally the tstat was just open, but i will try this.

just a pain in the arse because i had it all apart.........

07' JKUR rollin on 35s
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post #8 of 18 Old 04-25-2012, 02:07 PM
edpmedic
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27.5 is what I figured also it just had me thinking I must be counting wrong. I put a 195 in and it is only a little above 155. I put a Stant #36309. BT300 195. I never looked to see if that was the right one, but my heat is really hot from the vents. Then again it isn't winter anymore.

So either the sensor went from the overheating or I have the wrong thermostat, even if it says 195. I don't stay on fast idle, so I figure the temp sensor for the computer is ok.

Never4get those who gave their lives on 09-11-01 WTC and Pentagon. FDNY-EMS-NYPD-PAPD. Also those who are still dying.
_______________________________________________
"Freedom is never voluntarily given by the oppressor; it must be demanded by the oppressed."
Martin Luther King, Jr.
_______________________________________________
"Always aim at complete harmony of thought and word and deed. Always aim at purifying your thoughts and everything will be well."
Mahatma Gandhi
_______________________________________________
Feel the Sunshine on your face
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post #9 of 18 Old 04-25-2012, 09:08 PM Thread Starter
hdrocknroll
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Quote:
Originally Posted by edpmedic View Post
27.5 is what I figured also it just had me thinking I must be counting wrong. I put a 195 in and it is only a little above 155. I put a Stant #36309. BT300 195. I never looked to see if that was the right one, but my heat is really hot from the vents. Then again it isn't winter anymore.

So either the sensor went from the overheating or I have the wrong thermostat, even if it says 195. I don't stay on fast idle, so I figure the temp sensor for the computer is ok.
Sounds like the temperature sending unit, or the gauge is whacked, but I'm betting on the temperature sending unit.
Here is A couple more part numbers, Duralast,Auto zone, PN.TU236 Temp Switch.
And, NAPA part No. TS6685

Always !! Keep A Firm Grip On Your Tool !!

Watch Out For The Air Hose Gone Wild!! Or Wear A Cup,: True Story


Quote:
Originally Posted by rooster51 View Post
Whats the worse that can happen? Your jeeps already broke.


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post #10 of 18 Old 04-25-2012, 09:37 PM
ymerej88
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I just changed my tsu and gauge still isnt moving time to install after market gauge
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post #11 of 18 Old 04-26-2012, 01:41 PM
edpmedic
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Thanks I checked the Stat site
http://www.stant.com/Parts-Locator/ and it gives a different number, but when I checked the one I have it says OK for the Jeep. So I guess I will try the Sensor and see if that works. I did the temp gage sensor test and it is working. That don't mean it is accurate. At this point it is easier to change then the sensor then the stat, and I had trouble with the housing leaking. So I rather not disturb it if I don't have to.

Never4get those who gave their lives on 09-11-01 WTC and Pentagon. FDNY-EMS-NYPD-PAPD. Also those who are still dying.
_______________________________________________
"Freedom is never voluntarily given by the oppressor; it must be demanded by the oppressed."
Martin Luther King, Jr.
_______________________________________________
"Always aim at complete harmony of thought and word and deed. Always aim at purifying your thoughts and everything will be well."
Mahatma Gandhi
_______________________________________________
Feel the Sunshine on your face
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post #12 of 18 Old 04-26-2012, 09:19 PM
jaguarjoe
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Location: Grosse Ile
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The sending units for the gauge as well as for the PCM are "thermistors". They can be notoriously inaccurate, especially when Chyrsler/Jeep buy a million a year. They are, however, incredibly cheap to buy which is the main requirement at the factory. The gauge is better, but not by a whole lot.

To make all of this right, you'll need an ohmeter (digital is good), a pair of clip leads, and a variable resistor (from Radio Shack, ~10k ohms is prolly OK).

Connect the variable resistor to the harness connector and adjust it until the gauge reads what you think is 212 degrees F. Without being plugged into the harness and without disturbing the resistor, measure its value in ohms and write it down or make a mental note of it.

Buy a bunch of Senders (keep the receipt because all but one will be returned). Heat a small pot of water to boiling (212F) and one by one dip each Sender into the water while reading the Sender's resistance on you meter. When a Sender's resistance matches the gauge resistance noted earlier, you will then have a Sender calibrated to your particular gauge (at 212F, anyhow)

Once I thought that drinking beer was bad so I just stopped thinking
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post #13 of 18 Old 04-26-2012, 09:26 PM Thread Starter
hdrocknroll
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Join Date: Dec 2011
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Quote:
Originally Posted by jaguarjoe View Post
The sending units for the gauge as well as for the PCM are "thermistors". They can be notoriously inaccurate, especially when Chyrsler/Jeep buy a million a year. They are, however, incredibly cheap to buy which is the main requirement at the factory. The gauge is better, but not by a whole lot.

To make all of this right, you'll need an ohmeter (digital is good), a pair of clip leads, and a variable resistor (from Radio Shack, ~10k ohms is prolly OK).

Connect the variable resistor to the harness connector and adjust it until the gauge reads what you think is 212 degrees F. Without being plugged into the harness and without disturbing the resistor, measure its value in ohms and write it down or make a mental note of it.

Buy a bunch of Senders (keep the receipt because all but one will be returned). Heat a small pot of water to boiling (212F) and one by one dip each Sender into the water while reading the Sender's resistance on you meter. When a Sender's resistance matches the gauge resistance noted earlier, you will then have a Sender calibrated to your particular gauge (at 212F, anyhow)
That's why if ceramic is cracked ,it will be inaccurate

Always !! Keep A Firm Grip On Your Tool !!

Watch Out For The Air Hose Gone Wild!! Or Wear A Cup,: True Story


Quote:
Originally Posted by rooster51 View Post
Whats the worse that can happen? Your jeeps already broke.


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post #14 of 18 Old 05-01-2012, 08:04 AM
grkman1
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Join Date: Oct 2009
Location: Athens, Ga
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I have a problem with my temperature gauge also. I have already changed out the temp sensor next to the thermostat.

I am thinking my problem may stem from a sluggish thermostat. My temperature shows a little over the 210 middle line, but does on occasion run hotter a line, and in rare cases two lines over normal. It has not ever run into the red, BUT I help it out by turning off the A/C and running the heat to help cool the engine.

I plan on towing my Jeep in June for a cross country trip with my motorhome, and would like to resolve this issue before the trip.

Any suggestions as to what I could/should to would be most appreciated

Thanks
George
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post #15 of 18 Old 05-01-2012, 09:42 AM
sebian
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Location: Austin
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Quote:
Originally Posted by grkman1 View Post
I have a problem with my temperature gauge also. I have already changed out the temp sensor next to the thermostat.

I am thinking my problem may stem from a sluggish thermostat. My temperature shows a little over the 210 middle line, but does on occasion run hotter a line, and in rare cases two lines over normal. It has not ever run into the red, BUT I help it out by turning off the A/C and running the heat to help cool the engine.

I plan on towing my Jeep in June for a cross country trip with my motorhome, and would like to resolve this issue before the trip.

Any suggestions as to what I could/should to would be most appreciated

Thanks
George
You might want to start a new thread for this one. But off hand, I would check the condition of the fan clutch. Make sure that it operates properly. After that, I would look at the coolant, flush it if it looks questionable. Making sure to flush the radiator really well. That will also tell you if you have restricted flow, or just a ton of crap in it. While doing the flush, it would be a good time to change the t-stat. If it still runs too warm after that, you may have a failing water pump, or partial blockage on the cooling system.


For the OP, I have learned to avoid the Autozone temp sending units. They seem to run about 30* to high. I swapped in a Napa and it is much better.

1995 ZJ 5.2L V8 318. 230,000 miles and still rollin.

List of parts not replaced yet:
...
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