95 k1500 Temp Gauge/Sensor Issue

#1
Ok guys im new to this whole forum stuff so please forgive me if I am not doing this right. LOL
We have a 95 k1500 that we have been rebuilding for my son and we are having some problems with the temp guage not reading. When we got the truck it had an aftermarket temp guage on the A piller, it was a single wire running to the temp sensor located between cylinders on the drivers side of the engine. We removed the gauge on the a piller and found the cut wireing for the factory temp gauge. We then hooked the single wire up to one of the 2 cut leads and was able to get the stock guage to "work". Notfeeling super confident on the readings and not wanting to leave it half assed we purchased a new factory 2 wire sensor and replaced the single wire, spliced the new plug into the exesting wires and now we have nothing. No reading at all.
Do these wires have a "posative or negative" that I may have hooked up backwards?
Is there some other explination?
PLEASE HELP..........
 
#2
Although I don't know that particular truck, I would think going from a single wire to two wire sensor, you would need to ground one of the two connectors on the sensor to complete the circuit. There shouldn't be a difference between the two since it works as a variable resistance. You should try to find the electrical schematics and check for the wiring. I checked GM-SI and I can't get them. If you can find a Haynes, it should have it.

Going to a different sensor is also iffy if it uses different resistance to sense the temps. I'd try and find the proper sensor.
 
OP
OP
N
#3
Thats just it, we went from a aftermarket 1 wire sensor to the correct 2 wire factory sensor. Basicly taking the truck back to stock.
 

MRRSM

Gold Supporter
#4
These are excerpts from this link:

http://www.chevytalk.org/fusionbb/showtopic.php?tid/280356/

I have wonderful news. I was right when I said I didnt think there was anything wrong with the gauge. It was the sensors. They were all the wrong sensors (sounds crazy I know)but it is. Here is what I did to solve this:

I went to my local salvage yard and recorded every truck from 1989-1992, then I removed each sensor. There was 3 different style sensors I found. Button style, spade style, and weatherpack. Weatherpack started being OEM in 1991. Then I removed one of each sensor and ohm tested each. The button style and the weatherpack were the same, but the spade style is different in resistance. I got a weatherpack style to try in mine because it matched the button style I had originally. So long story short... My gauge is 100% accurate again. The reason why all the spade styles read 245 at 190 is because they all have the same resistance, but it is not the right resistance for the 1990. but is correct for the 1989. Here is the part number that is the correct sensor:

Sensor GM25037332

A pigtail will be required to convert from the button style to the weatherpack style. standard part number S963. When I get the GM number I will post it.
I am very happy all is good now. sensor and pigtail cost me nothing because they were used but at least if I go to replace it again I know what to get.
I keep this truck completely factory. No aftermarket. It takes work and time but it is completely worth it. Thanks all

Update:
just to clarify.
Sensor part number
GM 25037332
Pigtail
Standard S963. 1 pin. has room for 2 but only uses one. You can confirm the correct sensor by verifying the resistance. put 1 lead on the pin in the plug of the sensor, and the other anywhere on the sensor body. resistance should be 1425 at 100*f (cold) and should decrease as it warms up. I verified this by holding the tip in a cup of hot water. worked like a charm. Hope this helps and maybe a good sticky
 
OP
OP
N
#5
These are excerpts from this link:

http://www.chevytalk.org/fusionbb/showtopic.php?tid/280356/

I have wonderful news. I was right when I said I didnt think there was anything wrong with the gauge. It was the sensors. They were all the wrong sensors (sounds crazy I know)but it is. Here is what I did to solve this:

I went to my local salvage yard and recorded every truck from 1989-1992, then I removed each sensor. There was 3 different style sensors I found. Button style, spade style, and weatherpack. Weatherpack started being OEM in 1991. Then I removed one of each sensor and ohm tested each. The button style and the weatherpack were the same, but the spade style is different in resistance. I got a weatherpack style to try in mine because it matched the button style I had originally. So long story short... My gauge is 100% accurate again. The reason why all the spade styles read 245 at 190 is because they all have the same resistance, but it is not the right resistance for the 1990. but is correct for the 1989. Here is the part number that is the correct sensor:

Sensor GM25037332

A pigtail will be required to convert from the button style to the weatherpack style. standard part number S963. When I get the GM number I will post it.
I am very happy all is good now. sensor and pigtail cost me nothing because they were used but at least if I go to replace it again I know what to get.
I keep this truck completely factory. No aftermarket. It takes work and time but it is completely worth it. Thanks all


Update:
just to clarify.
Sensor part number
GM 25037332
Pigtail
Standard S963. 1 pin. has room for 2 but only uses one. You can confirm the correct sensor by verifying the resistance. put 1 lead on the pin in the plug of the sensor, and the other anywhere on the sensor body. resistance should be 1425 at 100*f (cold) and should decrease as it warms up. I verified this by holding the tip in a cup of hot water. worked like a charm. Hope this helps and maybe a good sticky

Ok mayby I am still not understanding. Are you saying that even though we ahve 2 factory wires leading to the sensor we should only be using 1?
 

MRRSM

Gold Supporter
#6
According to this comprehensive GM 1988-1998 Wiring Schematic... It looks like your Coolant Temp (SW?) is a Single Green Wire..(Instrument Panel Connector "R"). Look at the Image posted further down in the link I attached above for you to browse... It looks like it does have a Two Pin Connector all right... but it only uses One Wire for that guy's 1994 Engine. Go back and see for yourself:

2013-04-21_182325_88-98_ck_wiring2.jpg
 
OP
OP
N
#7
According to this comprehensive GM 1988-1998 Wiring Schematic... It looks like your Coolant Temp (SW?) is a Single Green Wire..(Instrument Panel Connector "R"). Look at the Image posted further down in the link I attached above for you to browse... It looks like it does have a Two Pin Connector all right... but it only uses One Wire for that guy's 1994 Engine. Go back and see for yourself:

View attachment 83189
So yes according to this diagram it should only be one wire. That means the parts store gave me the wrong sensor and plug. But this still does not explain why there are 2 wires coming from the harness to the sensor??
 

MRRSM

Gold Supporter
#8
Not necessarily... It may be that since you have not posted any images of exactly the areas and wiring and components involved so far... There is a possibility that we are talking about Two Completely Different ECTs. IIANM... The Dual Wire Sensor located in the forward area upper front on the Engine. ...a Wild Guess would be that if you find an ECT Sensor in that area... it will be of the Two Wire Flavor that communicates Coolant Temperature to and from the PCM. The Other Single Wire ECT Sensor located on the Driver's Side Engine Head communicates with the Dashboard Coolant Temperature Gauge. So until we can see exactly where you are working things on that engine and what the Cut Wires and their actual wiring Colors look like and what the other views of your situation look... we won't know what is what... or what to do about it.

If the Parts Dealer sold you an ECT Sensor that has two wire capability... he may not have understood which sensor you wanted to replace or picked the first one on the screen when he looked up the Year Make and Model of your vehicle. The other thing to consider is that if you were using the OEM version ...AC-Delco... the the part may be able to function in either a One Wire OR a Two Wire installation. You really need a Factory Manual or an All Data account to confirm this kind of information. Your Truck is 23 years old... so there are not many contemporary sources of imagery and parts-specific information that can be easily obtained without knowing as much information about your specific 95 K1500 Engine as possible. Getting to view real time images is a very big help in getting around such problems.
 
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OP
OP
N
#9
Not necessarily... It may be that since you have not posted any images of exactly the areas and wiring and components involved so far... There is a possibility that we are talking about Two Completely Different ECTs. IIANM... The Dual Wire Sensor located in the forward area upper front on the Engine. ...a Wild Guess would be that if you find an ECT Sensor in that area... it will be of the Two Wire Flavor that communicates Coolant Temperature to and from the PCM. The Other Single Wire ECT Sensor located on the Driver's Side Engine Head communicates with the Dashboard Coolant Temperature Gauge. So until we can see exactly where you are working things on that engine and what the Cut Wires and their actual wiring Colors look like and what the other views of your situation look... we won't know what is what... or what to do about it.

If the Parts Dealer sold you an ECT Sensor that has two wire capability... he may not have understood which sensor you wanted to replace or picked the first one on the screen when he looked up the Year Make and Model of your vehicle. The other thing to consider is that if you were using the OEM version ...AC-Delco... the the part may be able to function in either a One Wire OR a Two Wire installation. You really need a Factory Manual or an All Data account to confirm this kind of information. Your Truck is 23 years old... so there are not many contemporary sources of imagery and parts-specific information that can be easily obtained without knowing as much information about your specific 95 K1500 Engine as possible. Getting to view real time images is a very big help in getting around such problems.
Ok Sir. I will take and post pictures tomorrow. I GREATLY APPRECIATE all of your help AND patients.
Yes there are 2 locations. 1 on top of intake and 1 between #1and #3 cylinder (this is the one o am refuting to) again THANK YOU!
 
#10
Ok Sir. I will take and post pictures tomorrow. I GREATLY APPRECIATE all of your help AND patients.
Yes there are 2 locations. 1 on top of intake and 1 between #1and #3 cylinder (this is the one o am refuting to) again THANK YOU!
Ok so here is a picture of the location of the sensor as well as the 2 wires in question. It appears to me that one wire is Green in Color and the other is Blue. Is this the information you were looking for?
 

Attachments

Shaw520

Well-Known Member
#11
I think you have the wrong sensor,..ive only seen single green wire in that vintage,..could the blue wire from the harness be the dash/guage light?
 
#12
I think you have the wrong sensor,..ive only seen single green wire in that vintage,..could the blue wire from the harness be the dash/guage light?
Man at this point I think anything is possiable..... LOL Thank you for the input. If it is for the light im not sure where the other end would be?
 
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MRRSM

Gold Supporter
#13
The rational approach is to scour the Internet for some Engine Bay Wiring Schematics involving anything you can find for 1995 k1500 vehicles. Also... IIANM if you’re Engine has Throttle Body Injection... There should be two wires...one Green and one Blue connecting to the Injectors contacts ...one on each side... look there first to ensure that two wire insulated harness is not missing ... and spend some time Googling that expression for as many wiring diagrams as you can find...
 
#14
The rational approach is to scour the Internet for some Engine Bay Wiring Schematics involving anything you can find for 1995 k1500 vehicles. Also... IIANM if you’re Engine has Throttle Body Injection... There should be two wires...one Green and one Blue connecting to the Injectors contacts ...one on each side... look there first to ensure that two wire insulated harness is not missing ... and spend some time Googling that expression for as many wiring diagrams as you can find...
We will give it a try..
Thank You