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Discussion Starter #1 (Edited)
Good evening. I been doing some work on my cluster and under dash. I fixed my oil pressure guage a couple days ago. Today, I installed a new ignition switch box that goes on the top of the column. Today, when I was doing that, I noticd I lost my temperature guage.

The temperature guage used to always work and was working yesterday. At idle, when the temp would get about 3/4 the fan would come on. Not no more. I feel like I’m waiting until the engine is hot enough for the fan to kick on. The needle does bounce to high as the engine is turning over but flips back down as car begins to run. Now no temp (always reads cold when car is on or key is on) and no fans kick on after waiting for a while so I kill the engine so I don’t over heat. As per FSM, I tested the connector plug at A4 behind the right side of the cluster, vehicle side( black plug). I get no voltage. Dark green wire as per FSM the manual says anyway. I did a FSM test on terminal A on the water pump sensor plug and I think it tested good. My battery is not very good and I been using a charger so don’t know exact voltage. I think I got like 8.6 volts and it matched my battery charger. I did change that water pump temp sensor before I know that much. I never changed the one below the manifold

*** I was reading on the forum where somebody says pull the plug connector off the water temp sensor on the side of the block. It’s one wire. They said ground it and the guage should go up to hot when Car is on. I did that and it does go up to hot.

Does this mean that the temp sensor happened to fail as I’m in the middle of this work?

Why am I not getting voltage at C2 A 4 right side of cluster. Is this because the sensor IS bad? Will I get voltage at A4 if I change the sensor? Thanks. Need input
 

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"I was reading on the forum where somebody says pull the plug connector off the water temp sensor on the side of the block. It’s one wire. They said ground it and the guage should go up to hot when Car is on. I did that and it does go up to hot." The car also shorts the sensor wire(green) every time the engine cranks. That is why : "The needle does bounce to high as the engine is turning over but flips back down as car begins to run. "

So your gauge seems to work for two different tests.

The gauge sensor when unplugged should read 1356 Ohms at 100 degF (warm) (meter in 2000 Ohms) and 55 Ohms at 260 deg F (very hot) (meter in 200 Ohms). One probe on the sensor pin and one on the metal body. Sensor will not work if it does not have a good ground to the block.(no Teflon tape on the threads)

The sensor on the water pump is for the PCM. The PCM runs the fans. If you unplug the temperature sensor on the water pump BOTH radiator fans should run with the engine running. The turning on the A/C may start the fans as well.

Do not waste your time by doing anything if the battery does not have 12 Volts with the engine off key on. A bad battery will mess with you.
 

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Discussion Starter #3 (Edited)
M
"I was reading on the forum where somebody says pull the plug connector off the water temp sensor on the side of the block. It’s one wire. They said ground it and the guage should go up to hot when Car is on. I did that and it does go up to hot." The car also shorts the sensor wire(green) every time the engine cranks. That is why : "The needle does bounce to high as the engine is turning over but flips back down as car begins to run. "

So your gauge seems to work for two different tests.

The gauge sensor when unplugged should read 1356 Ohms at 100 degF (warm) (meter in 2000 Ohms) and 55 Ohms at 260 deg F (very hot) (meter in 200 Ohms). One probe on the sensor pin and one on the metal body. Sensor will not work if it does not have a good ground to the block.(no Teflon tape on the threads)

The sensor on the water pump is for the PCM. The PCM runs the fans. If you unplug the temperature sensor on the water pump BOTH radiator fans should run with the engine running. The turning on the A/C may start the fans as well.

Do not waste your time by doing anything if the battery does not have 12 Volts with the engine off key on. A bad battery will mess with you.
I pulled my sensor from my head, broke the little plastic receiver for the connector on the sensor. All I can say is when I test the sensor cold, it does not give a reading. When I put it under hot water from the faucet I get numbers near 2000. When I put a torch to it, I get numbers below 100. Can this sensor be bad? I have to get a new one anyways. I have no way of boiling water to 100f exactly or the other side of that need for the other measurement. Seems like the sensor worked. I wonder if the ground between the sensor and head got removed somehow. On another thread on my gas guage thread, forget who told me to disconnect the ground in the trunck to see what the gas guage does. I did it and I could hear my door locks buzzing and fuel guage shot up. That’s the only thing I can think of that may have did something since It was working last

Notes. C2 A4 no power like book says with sensor connected last time checked. When I ground the plug itself the guage flips up. So I’m guessing that’s good. I’m thinking that with the grounded plug and testing A4 again, it will test light 💡 on. Don’t want to count on it though. Idk how but when I plug the sensor on broken like it is, it seems like the terminal metal contacts are loose. I had someone look at the guage, with car on. I wiggled it to see if it would get conduction, “nothing” I’m stumped. Next I’m getting a new sensor tomorrow. For the pictures.

The “l” is cold with no reading.
The low number (3 digit) is hot hot.
The 1333 is cooling off towards 100F I guess.
Can see numbers move. Wonder if cold is supposed to have a reading?????
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"The “l” is cold with no reading." This is normal for the Ohm range you selected. You might get a number if you select 2000K. The two other tests also seem good. Seeing the numbers moving up and down also sound good. Bonus points for taking the time to check the sensor but I am betting on: "plug the sensor on broken like it is, it seems like the terminal metal contacts are loose." The circuit path is from the metal threads on the sensor to the engine. So again threads should be clean. The engine should have a good ground from the negative battery cable.

Again I think you have proved the gauge is OK. Your ground test and the "self test" when the ignition switch is in start.

"told me to disconnect the ground in the trunck to see what the gas guage does. I did it and I could hear my door locks buzzing" I again suggest you make sure the negative(ground) wire from the battery to the right fender is in good shape and the connection is clean. It is the only way the car body gets a good ground from the battery.
 

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Discussion Starter #5
Thanks for the reply. I do need to change my negative cable. I may do that before I put coolant back in my car so I can get under the coolant tank for routing. Here is a pic of my new sensor from autozone with part number on box. For anyone concerned with a two prong connector and the one prong plug on our cars. My previous connector had the two prong sensor and worked for the last 8 or so years. It’s been on the car since I’ve had it. This new one is identical from Autozone with a Lifetime Guarantee. Life time is why I got a Duralast. It should work. I’ll be sure to let anyone know if it’s not a good buy. They said it’s guaranteed even if the plastic boot part breaks. So, That’s why I like autozone for parts like this. I’m not rich so whatever by choice. I didn’t use autozone Opti or fuel sending units though. *Last thing. My gauge needle is on way down under cold since it’s not working. Should my guage go up to at least the cold mark with this new sensor providing I have the body of the sensor grounded?
"The “l” is cold with no reading." This is normal for the Ohm range you selected. You might get a number if you select 2000K. The two other tests also seem good. Seeing the numbers moving up and down also sound good. Bonus points for taking the time to check the sensor but I am betting on: "plug the sensor on broken like it is, it seems like the terminal metal contacts are loose." The circuit path is from the metal threads on the sensor to the engine. So again threads should be clean. The engine should have a good ground from the negative battery cable.

Again I think you have proved the gauge is OK. Your ground test and the "self test" when the ignition switch is in start.

"told me to disconnect the ground in the trunck to see what the gas guage does. I did it and I could hear my door locks buzzing" I again suggest you make sure the negative(ground) wire from the battery to the right fender is in good shape and the connection is clean. It is the only way the car body gets a good ground from the battery.
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Discussion Starter #6
Well, I’ve put my new sensor in and it still does the same thing. Key off cold mark, key on position below cold mark. Cranking action position flips to hot during that and flips back down below cold while running. I do believe the key off position rises as the temp of the car engine increases. If it’s an accurate reading I don’t know. Who wants to turn their car off to see how hot it is anyways. Notes: My fans have not came on since this happened and I don’t want to wait for them to come on either as I may over hear doing so. This is a bummer. I guess as that person said on the other thread that if grounding the single wire makes the guage go up, then it’s the sender is not absolutely true as I’ve replaced it with no luck in that. Maybe my block is not grounded good? I guess that’s where I will start again. That strap ground behind the drivers side head. I noticed this temp guage failure as I was electrical taping my harness behind the glove box where the oil pressure guage resistor is. I started my car to charge the battery and no temp reading. Wow, if it is not one thing it’s another I guess. Anyone know if I can bench test the temp guage and how? Or has that been done by grounding the single plug wire?
 

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Discussion Starter #7
I didn’t put my ground cable on yet by the way as I stated I would. It isn’t in that bad shape that I needed too. I know the ground can use another crimped eyehole connector at the fender. I’m going to replace it because the connector has a tear “tere” in the base of it like its been twisted at tad.
 

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Discussion Starter #10
Question: How can B4 be a ground according to the book (above photo) and there is no contact in my B4 port terminal contact area on my right C2 connector plug? Is it A6 on my car?
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Discussion Starter #11
I guess I was testing the wrong holes. Correct me if I’m wrong but I now believe it’s the inner top and below sets of pin holes.?? Pic provided of my thoughts on the correct holes. Wonder what the top top and bottom
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bottom is for?
 

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Discussion Starter #12
If A4 is the sender and B6 is the ground (one of the grounds according to FSM at least) shouldn’t I get an ohm’s reading as the car warms up if I put the red probe in A4 and the black probe in A 6? Feedback welcome.
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Discussion Starter #13
For what it’s worth, A6 (ground tests good to cig lighter center pin. I don’t know how to test A 4 for being a closed circuit (no shorts or non-connects/splits in the wire to the sensor/sender. Then this brings the whole grounding to the head and all.
 

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Discussion Starter #14
For what it’s worth, A6 (ground tests good to cig lighter center pin. I don’t know how to test A 4 for being a closed circuit (no shorts or non-connects/splits in the wire to the sensor/sender. Then this brings the whole grounding to the head and all.
 

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Take a look at the pictures same idea as the oil gauge there are only metal contacts in the outer row.

The dark green wire connects the temperature sensor to the gauge and the self test switch on the ignition. With the key out C2A4 and the green wire at the ignition should be Zero Ohms.

You have gauge movement when you shorted the sensor lead to ground. The self test works when you crank the engine. The circuit wires are good the sensor is new.

If the fans do not turn on and the gauge does not show heat maybe they are correct. Have you bleed the coolant at the thermostat? Maybe you have air instead of coolant in the top of the engine.
 

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Discussion Starter #17
Are you stating C2 A4 should be zero ohms with this green wire on the ignition switch above the column with the key out? And, which probe (black or red) on green wire “at ignition” if true. What meter ohm setting..eg “200” “2000”.
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Discussion Starter #18
If you look closely there are metal contacts on inner row. It seems like they are not there but they are. You have to aim the light correctly. It’s a shadow that makes it look like there is not. If you look closely at the back of the cluster, you see (from the top bottom spacing) the pins mate with the inner row of contacts on the C2 plug connector. The inner contacts are even boxed in to “spring action” around the pins on the cluster.
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Discussion Starter #19
H
Take a look at the pictures same idea as the oil gauge there are only metal contacts in the outer row.

The dark green wire connects the temperature sensor to the gauge and the self test switch on the ignition. With the key out C2A4 and the green wire at the ignition should be Zero Ohms.

You have gauge movement when you shorted the sensor lead to ground. The self test works when you crank the engine. The circuit wires are good the sensor is new.

If the fans do not turn on and the gauge does not show heat maybe they are correct. Have you bleed the coolant at the thermostat? Maybe you have air instead of coolant in the top of the engine.
How can your photo C2 A4 be correct for the “right side” cluster C2 connector? Your photo shows an A row, 4th terminal counting from the left. My FSM provided photo of the “right side” cluster C2 states A4 is counted from the right to left- not left to right. Correct me if I’m wrong but I conflict with your “A4” location. Unless you meant to explain something else??
 

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If you look closely there are metal contacts on inner row. It seems like they are not there but they are. You have to aim the light correctly. It’s a shadow that makes it look like there is not. If you look closely at the back of the cluster, you see (from the top bottom spacing) the pins mate with the inner row of contacts on the C2 plug connector. The inner contacts are even boxed in to “spring action” around the pins on the cluster. View attachment 191914
Look at the round lugs in the schematic
Now look at the plug in the picture
That plug ( 99% sure because I put all my stuff away and am not pulling it back out)
TOP ROW Left to right is B1 B2 B3 etc
Looking at it that way I see the correct pins and missing pins.

All that being said as already explained to you, if the guage goes full scale in each direction when you ground the green wire then unground it, it is OK.

As also said , change your battery, stop screwing around with battery chargers.
You are asking for trouble and wild goose chases

Fix all the underhood grounds, make sure you have a good ground , battery to block, battery to frame , battery to body,

Then start looking for issues.

As ALSO said, if the fans aren't coming on, maybe it isnt warming up OR you have a bunch of air in there.

To underline.
Mucking around with less than , or in the case of a battery charger, more than correct stable voltage is just begging for confusing information and possible damage
 
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