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Unread 04-23-2012, 11:54 PM   #1
hdrocknroll
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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

18970646_bwd_wt430_pri_thmb.jpg

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

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Unread 04-24-2012, 11:29 AM   #2
sebian
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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!
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Unread 04-24-2012, 11:38 AM   #3
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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Unread 04-24-2012, 04:05 PM   #4
edpmedic
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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.
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Unread 04-24-2012, 04:34 PM   #5
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.
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Unread 04-24-2012, 05:04 PM   #6
dean477
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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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Unread 04-24-2012, 11:23 PM   #7
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.........
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Unread 04-25-2012, 03:07 PM   #8
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.
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Unread 04-25-2012, 10:08 PM   #9
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
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Unread 04-25-2012, 10:37 PM   #10
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I just changed my tsu and gauge still isnt moving time to install after market gauge
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Unread 04-26-2012, 02:41 PM   #11
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.
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_______________________________________________
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Unread 04-26-2012, 10:19 PM   #12
jaguarjoe
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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)
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Unread 04-26-2012, 10:26 PM   #13
hdrocknroll
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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
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[QUOTE=rooster51;13297693] Whats the worse that can happen? Your jeeps already broke.



[/QUOTE]
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Unread 05-01-2012, 09:04 AM   #14
grkman1
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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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Unread 05-01-2012, 10:42 AM   #15
sebian
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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.
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