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Discussion Starter · #1 ·
I have a 93 5.7 that I swapped to a 6.5. I am having an issue with the coolant temp indicator. The ect sensor is new. On start up the indicator reads cold, and after about a minute of Idle the temp begins to come up. Once the needle reaches the area of the guage that has some numbers, the needle quickly pegs completely hot. The engine is still pretty cold, and the resistance of the ect sensor is maybe around 800-1000 ohms when I have checked it. If I unplug it the guage pegs cold again. If I short the green wire to ground, the sensor of course pegs hot. I have replaced the cluster with a junkyard unit and still have the exact same problem. I have pulled apart the cluster, and traced the circuit. There is a 10 ohm resistor (by code) that is accurate on the small pcb with the logic chips on it. And there is no break or excessive resisistance in the traces to the guage. I have pulled the cluster, and directly hooked up power and ground to their pegs, and a jumper from the ect sensor to the S peg on the back of the guage. when I started the vehicle, I had the exact same symptom. Can anyone tell me what I am missing?
 

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When you replaced the ECT Sensor did you use an AC/Delco brand replacement?
 

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What sensor are you testing. The one on top of the thermostat housing is a switch that controls the GP/ cold start system.
There is another sensor for the gauge on left cylinder head.
 

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Discussion Starter · #4 ·
I replaced it with
When you replaced the ECT Sensor did you use an AC/Delco brand replacement?
Thanks for responding guys. I replaced it with a rock auto one, not an AC delco. However by checking resistence, for the guage to read full hot the resistence of the sensor would've had to be much lower than the 800-1000 it read when I checked it. And the temperature was roughly equivalent to correct ohms for that temp.
 

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Discussion Starter · #5 ·
What sensor are you testing. The one on top of the thermostat housing is a switch that controls the GP/ cold start system.
There is another sensor for the gauge on left cylinder head.
Thanks for responding. I am aware of the temp switch, and the temp sending unit. I was indeed checking the one on the left head towards the front.
 

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Discussion Starter · #6 ·
Not sure if anyone knows the values, but if perchance. I measured resistances on the guage pegs as follows: S= sender, I=Ignition voltage, G= ground. S-I 35.5 ohms, G-I 128.2 ohms, S-G 164.1 ohms. Maybe someone can confirm a good or bad guage based on that?
 

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I replaced it with

Thanks for responding guys. I replaced it with a rock auto one, not an AC delco. However by checking resistence, for the guage to read full hot the resistence of the sensor would've had to be much lower than the 800-1000 it read when I checked it. And the temperature was roughly equivalent to correct ohms for that temp.
Any part that is electrical in nature needs to be AC/Delco. Aftermarket brands will bring in electrical gremlins into the mix and add to the problems when trying to diagnose an issue
 

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Discussion Starter · #8 ·
Any part that is electrical in nature needs to be AC/Delco. Aftermarket brands will bring in electrical gremlins into the mix and add to the problems when trying to diagnose an issue
Well, I appreciate the input, I stand by my multimeter reading in this case. I still dont beleive the sending unit could be causing this particular problem. I just took the cluster out, and read directly ohms through the harness and etc sensor from about 1500 slowly down to 212 as the engine warmed up. granted I had run the engine a bit a little while ago, so it wasnt completely cold. neverthe less the ohms are what they are supposed to be. I don't see how the etc sensor could be causing the guage to read so high so soon.
 

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Discussion Starter · #9 ·
Seeing the temperature resistance chart, I was getting about 1500 ohms when the gauge went full hot, but it shouldn't have gone full hot until well below 170 ohms. I guess I just don't know what direction to go in after this except to try another cluster. Unless someone knows a way to bench test the guage.
 

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Well, I appreciate the input, I stand by my multimeter reading in this case. I still dont beleive the sending unit could be causing this particular problem. I just took the cluster out, and read directly ohms through the harness and etc sensor from about 1500 slowly down to 212 as the engine warmed up. granted I had run the engine a bit a little while ago, so it wasnt completely cold. neverthe less the ohms are what they are supposed to be. I don't see how the etc sensor could be causing the guage to read so high so soon.
The gauge could be pegging out due to the materials used in the making of the aftermarket part..
The only way you're going to rule out the sensor is to replace it with an OEM part ( AC/Delco)
 

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If you head to the junkyard again pick up a couple used ones. Is there a part number on your sender to make sure you have the correct one? Probably not the case but I did a idiot light swap to a guage swap in a GM car years ago and the wrong sending unit caused this to happen.
 

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Just to clarify things, Are you are using a cluster from a diesel 6.5 truck?
 
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Discussion Starter · #13 ·
Just to clarify things, Are you are using a cluster from a diesel 6.5 truck?
Actually all of you guys may be on to something. (and I feel a little dumb for not thinking of this before) The cluster is still the gasser version, and I'm sure the ect sendor is for the diesel. I just looked on Rockauto and the AC/Delco sending unit that is a 1 wire unit is actually the same part # listed for both the diesel and the gas for the 1993 years. (you guys know that AC/Delco outsources a lot of their parts nowadays right? Case In point, I bought an AC/Delco brand reman starter, and it lasted 2 whole years of light use before the solenoid went kaput....When I ordered another cheapie reman starter guess what...they were the same starter, only difference was the AC/Delco name stamped on the one....) Anyways, back to the point, I'll order the AC/Delco sending unit and see what happens. Shanejeep5 unfortunately around here none of the junkyards have any 6.5's, everytime I have checked they don't show up here. To get used parts I always have to ship them in.
 

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Ok heres the issue. GM used 3 different temp sensors for the temp gauge in V8s 2 types, ones with the spade connector and the ones with button connector are the same resistance value.
In the early 1990s GM went to the weatherpac. connector sensor,. like the type on 6.5 engines. They have a different resistance value. So the gauge that works with the weatherpac connector sensor is calabrated different than older gauges. So if you are using a cluster out of a gasser. or 6.2 you will need the older type single wire temp sensor that works with the gauge.
 

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Discussion Starter · #15 ·
Ok heres the issue. GM used 3 different temp sensors for the temp gauge in V8s 2 types, ones with the spade connector and the ones with button connector are the same resistance value.
In the early 1990s GM went to the weatherpac. connector sensor,. like the type on 6.5 engines. They have a different resistance value. So the gauge that works with the weatherpac connector sensor is calabrated different than older gauges. So if you are using a cluster out of a gasser. or 6.2 you will need the older type single wire temp sensor that works with the gauge.
I have the one with the single wire connector. That one came with the harness that was native to the gasser truck, so I ordered the same style. The single wire style is the same for the 6.5 diesel, and the gasser from 1993 according to rock auto. This truck is a 1993 body. If this does not work, which do you think I should try?
 

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Discussion Starter · #16 ·
Ok heres the issue. GM used 3 different temp sensors for the temp gauge in V8s 2 types, ones with the spade connector and the ones with button connector are the same resistance value.
In the early 1990s GM went to the weatherpac. connector sensor,. like the type on 6.5 engines. They have a different resistance value. So the gauge that works with the weatherpac connector sensor is calabrated different than older gauges. So if you are using a cluster out of a gasser. or 6.2 you will need the older type single wire temp sensor that works with the gauge.
this is a picture of the connector, and the sendor that is currently installed.
 

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Get the sender that matches the year make and model the cluster came out of. And specify guage and not idiot lights, I belive they offered at least 2 styles in 93
 

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The sender in your pic is the weather pac connection sender .It will not work with older gauge cluster. You need the single spade connector that looks like this one made for the 6.2 diesel or similar:
More Information for WALKER PRODUCTS 2141004
Dont use the part# on one in pic. I think it is for the idiot light. just put it there for reference. Get the sender that specifies" gauge".
. i'm pretty sure it has the same threads as the weather pac type
Just clip off the weather pac connector and use a spade connecter to plug it in.
EDIT Here is the one for a 6.2 diesel with gauge. It is also the same as gasser engines IIRC.
More Information for STANDARD MOTOR PRODUCTS TS76T
 
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Did they change from spade to weather pack from 93 to 94? I checked my 94 and it is weather pack with one wire but looks like it could hold 2 wires as its kinda Oval shape.
 

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Discussion Starter · #20 ·
Ok, thanks for the wealth of info, Sender with the spade has been ordered. Without you guys I think It would've been hard to track this info down!

The sender in your pic is the weather pac connection sender .It will not work with older gauge cluster. You need the single spade connector that looks like this one made for the 6.2 diesel or similar:
More Information for WALKER PRODUCTS 2141004
Dont use the part# on one in pic. I think it is for the idiot light. just put it there for reference. Get the sender that specifies" gauge".
. i'm pretty sure it has the same threads as the weather pac type
Just clip off the weather pac connector and use a spade connecter to plug it in.
EDIT Here is the one for a 6.2 diesel with gauge. It is also the same as gasser engines IIRC.
More Information for STANDARD MOTOR PRODUCTS TS76T
 
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