Thermal Sensor

Can anybody give the part # for the thermal sensor that threads into the thermostat housing? I went to Discount and ofcourse, left with the wrong one. I would prefer a Discount part# so I only have to make one trip but wouldn't mind if anybody has one for NAPA. I know I know, "you should have went to NAPA in the first place." Any help is ALWAYS appreciated!

What kinda vehicle ? Year, make, model, engine size?

Tim_MN said:

What kinda vehicle ? Year, make, model, engine size?

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Rookie mistake, sorry!

96XJ,6cyl, HO

NAPA Online lists the part as:

Coolant Temperature Sensor TEM 207857

CharlesS said:

NAPA Online lists the part as:

Coolant Temperature Sensor TEM 207857

Click to expand...

I think they gave me the one for the back of the motor, Its twice as big as the one I need? Does anybody know what that one is called?

The one I need threads into the thermostat housing and talks to the gauge in the dash?

I'm sure one of the other guys will get back on this but will go ahead and clarify:

The sensor that mounts in the thermostat housing provides a signal to the PCM (computer).

The sender that mounts in the rear of the head by the firewall sends data to the temp gauge.

Pelican said:

I'm sure one of the other guys will get back on this but will go ahead and clarify:

The sensor that mounts in the thermostat housing provides a signal to the PCM (computer).

The sender that mounts in the rear of the head by the firewall sends data to the temp gauge.

Click to expand...

Well the PO did some playing around, because the one that goes into the thermostat housing is discoed right now and my days gauge IS NOT moving??? Is this possible and if so why???

One thing that often happens is the parts store clerk gives you the sender for the idiot light instead of the gauge. I don't recall offhand whether this causes the gauge to not move or to peg.

Beyond that, of course, you could have a bad connection, broken wire, faulty gauge or bad sender.

Did the PO mess with the wiring?

I know the original sensor is broken because I broke it in half. At the same time, my gauge stopped working. I also know they gave me the wrong part because the sensor they gave me is easily twice the diameter that is in there now. What should I be asking for?

Do a search in the online store under temperature sensors for your year.
You will be given several choices.

Went back and got the "temperature gauge sending unit". Fits like a glove and it even came with a little bit of dry conductive lube on the back end of the threads. Now for the interesting part. My gauge is reading a little hotter than it originally was under similar conditions. Prior, I was hovering around 185-195 which led me to believe the PO had installed a 180 degree thermostat. Now, its reading 205-215 under similar conditions. I attribute this to a few different things.

1. The PO used Teflon tape on the sensor. I was always told that sensors that only have one wire ground to whatever they're threading into, so using Teflon tape creates a poor grounding situation. That's why the new one came with a conductive lube.

2. The PO for some reason cut and spliced the original wire to a newer connector, It was poorly crimped with some of the bare wire showing.

3. I threaded the sensor in deeper. Though they are the same lengths, I threaded mine in a 3-5 mm deeper.

4. It was an old sensor.

When I splice wires, I always fold and twist, solder, crimp, heat shrink and then electrical tape. Overkill I know, but I've NEVER had a splice come loose plus this was spliced just a few inches from the sensor only inches away form the fan, belt, etc....that pool little splice was taking a beating.

Hope this helps, thanks for every bodies input:exclamati

Pelican said:

One thing that often happens is the parts store clerk gives you the sender for the idiot light instead of the gauge. I don't recall offhand whether this causes the gauge to not move or to peg.

Beyond that, of course, you could have a bad connection, broken wire, faulty gauge or bad sender.

Did the PO mess with the wiring?

Click to expand...

Pelican said:

I'm sure one of the other guys will get back on this but will go ahead and clarify:

The sensor that mounts in the thermostat housing provides a signal to the PCM (computer).

The sender that mounts in the rear of the head by the firewall sends data to the temp gauge.

Click to expand...

My thermostat housing is threaded with two sensors. There is a small one that threads right into the front that was talking to my gauge. There is a larger one that threads into the side of the thermostat housing. What does that on talk to?

Firstly, there is no question about an unmodified setup: There is one sensor that screws into the thermostat housing and that sensor sends data to the computer only.

The gauge is fed in various ways depending on model year. The stock setup for the '96 has a sender that threads into the rear of the head. At some point they did away with this and the PCM talks directly to the gauge based on data collected from the thermostat sensor.

I have to assume that the head on your motor has been swapped out and a PO mounted the gauge sending unit into the tstat housing. Nothing wrong with that setup. There is a thread floating around right now or within the past several days covering that exact situation and where to mount a sending unit for a gauge.

Renix
Coolant temp SENSOR in lower block - to ECU
Aux. fan SWITCH in radiator - to fan relay
Temp SENDER - rear of head - to gauge

91 - 96 1/2

Temp SENDER - rear of head - to gauge
Temp SENSOR - t-stat housing - to ECU

96 1/2 -> Temp SENSOR in t-stat housing - to all via ECU

There were never 2 sensor/senders in the t-stat housing.

ParadiseXJ said:

Renix
Coolant temp SENSOR in lower block - to ECU
Aux. fan SWITCH in radiator - to fan relay
Temp SENDER - rear of head - to gauge

91 - 96 1/2

Temp SENDER - rear of head - to gauge
Temp SENSOR - t-stat housing - to ECU

96 1/2 -> Temp SENSOR in t-stat housing - to all via ECU

There were never 2 sensor/senders in the t-stat housing.

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If you look at a 96 thermostat housing, there are "2" threaded fittings. I verified this at two different parts stores, one of which being NAPA. The smaller of the two "on mine anyway" talkes to the gauge for sure, I'm not sure what else it talks to. The second threaded fitting to the right of the first, is larger "x2" and is threaded into the side of the thermostat housing. It IS a sensor of some sort. IT is part of a larger wire loom that runs over the top of the injector rail. What does THAT sensor talk to? I KNOW the PO replaced the head. He owns a local shop with a good reputiation. He bought it from a kid that cracked the head.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Water-Outlet/_/R-BK_6051754_0403498027

bugout said:

If you look at a 96 thermostat housing, there are "2" threaded fittings. I verified this at two different parts stores, one of which being NAPA. The smaller of the two "on mine anyway" talkes to the gauge for sure, I'm not sure what else it talks to. The second threaded fitting to the right of the first, is larger "x2" and is threaded into the side of the thermostat housing. It IS a sensor of some sort. IT is part of a larger wire loom that runs over the top of the injector rail. What does THAT sensor talk to? I KNOW the PO replaced the head. He owns a local shop with a good reputiation. He bought it from a kid that cracked the head.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Water-Outlet/_/R-BK_6051754_0403498027

Click to expand...

Looking at the NAPA part, I only see the one threaded sensor location which inserts the sensor into the coolant stream to the heater core. The second hole in the picture is a mounting hole, not a threaded location.

All of the OBDII 4 Liter XJs use the same water outlet. In the OBDII vehicles, the sensor feed a voltage to the PCM via a pair of wires. The sensor does not require grounding as it is a thermistor. As the temperature changes, the resistance in the sensor changes and so the voltage the PCM sees changes. The PCM uses a look up table to determine the coolant temperature which is reported as "ECT" on an OBDII scanner.

ODBII vehicles all share the same part number for the sensor be the engine a Diesel, the 2.5L or the 4.0L. Chrysler finally figured out that is was less expensive to have one sensor to do both functions. So, they use the same sensor to drive a gauge or the idiot light. Which is why it is possible to swap out the dash cluster from idiot lights to the full gauged cluster. No sensor changes required.

NAPA lists only one sensor for the '96 model year. They list the same part number for the '95 model year as well. Looks like the water outlets are the same for the H.O. engines as well.

So, perhaps a photo of your engine would have some value here...

O-Gauge Steamer said:

Looking at the NAPA part, I only see the one threaded sensor location which inserts the sensor into the coolant stream to the heater core. The second hole in the picture is a mounting hole, not a threaded location.

All of the OBDII 4 Liter XJs use the same water outlet. In the OBDII vehicles, the sensor feed a voltage to the PCM via a pair of wires. The sensor does not require grounding as it is a thermistor. As the temperature changes, the resistance in the sensor changes and so the voltage the PCM sees changes. The PCM uses a look up table to determine the coolant temperature which is reported as "ECT" on an OBDII scanner.

ODBII vehicles all share the same part number for the sensor be the engine a Diesel, the 2.5L or the 4.0L. Chrysler finally figured out that is was less expensive to have one sensor to do both functions. So, they use the same sensor to drive a gauge or the idiot light. Which is why it is possible to swap out the dash cluster from idiot lights to the full gauged cluster. No sensor changes required.

NAPA lists only one sensor for the '96 model year. They list the same part number for the '95 model year as well. Looks like the water outlets are the same for the H.O. engines as well.

So, perhaps a photo of your engine would have some value here...

Click to expand...

Thank you O-Gauge, your input is always welcome. I do not have a picture but I have found a link to a set up that is exactly like mine. The only difference is the bolt sticking out of the front of this one. Where that bolt is on mine, is the sensor that I replaced. That one was for a fact talking to my gauge. The one on the right is the one that I'm trying to figure out.
http://www.google.com/imgres?q=1996...202&start=0&ndsp=54&ved=1t:429,r:36,s:0,i:194

Hesco sells (or at least used to) a tstat housing with a second threaded bung; I don't think any stock housings had 2 threaded bungs. Adding one is pretty simple though, as mentioned earlier in this thread.

http://www.naxja.org/forum/showthread.php?t=1045608

At least the way you describe it, what the PO did was not what I consider a good idea. That would mean you have only one bolt on your tstat housing, which strikes me as bad.

O-Gauge Steamer said:

Looking at the NAPA part, I only see the one threaded sensor location which inserts the sensor into the coolant stream to the heater core. The second hole in the picture is a mounting hole, not a threaded location.

All of the OBDII 4 Liter XJs use the same water outlet. In the OBDII vehicles, the sensor feed a voltage to the PCM via a pair of wires. The sensor does not require grounding as it is a thermistor. As the temperature changes, the resistance in the sensor changes and so the voltage the PCM sees changes. The PCM uses a look up table to determine the coolant temperature which is reported as "ECT" on an OBDII scanner.

ODBII vehicles all share the same part number for the sensor be the engine a Diesel, the 2.5L or the 4.0L. Chrysler finally figured out that is was less expensive to have one sensor to do both functions. So, they use the same sensor to drive a gauge or the idiot light. Which is why it is possible to swap out the dash cluster from idiot lights to the full gauged cluster. No sensor changes required.

NAPA lists only one sensor for the '96 model year. They list the same part number for the '95 model year as well. Looks like the water outlets are the same for the H.O. engines as well.

So, perhaps a photo of your engine would have some value here...

Click to expand...

hubs97xj said:

Hesco sells (or at least used to) a tstat housing with a second threaded bung; I don't think any stock housings had 2 threaded bungs. Adding one is pretty simple though, as mentioned earlier in this thread.

http://www.naxja.org/forum/showthread.php?t=1045608

At least the way you describe it, what the PO did was not what I consider a good idea. That would mean you have only one bolt on your tstat housing, which strikes me as bad.

Click to expand...

Correction, mine is wired Exactly like the top picture it that thread. I do have a the bolt, I apologize. So, what does the sensor on the right do???

The sensor with 2 wires, sticking out of the driver's side of the housing, is the one OGS refers to, used by the PCM.