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WaterInYuhDish
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MAR 23, 08:34 PM
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EDIT: After letting it sit over night and driving this morning, the gauge doesn't move past 100 and after a few minutes of driving the coolant light comes on... will be relooking through pennocks for previous posts to find out what's going on but if anyone is willing to link me or talk to me about this, I'd appreciate it as now the chances of overheating my engine seem much higher HA
I posted this without verifying that the light came on after warm up... sorry 
"Just put in the correct temp gauge sending unit sensor for the dash because a PO put in the wrong sensor and I think I wired the connector backwards because now the coolant temp light on my dash is on all the time but the gauge doesn't move. Before it didn't work at all, no light, no gauge movement. So now at least I'm getting something on the dash, just want to make sure my engine isn't running hot and the gauge just doesn't work or something. Just double checking here for confirmation. If that's not it, any advice or links are extremely appreciated. Thanks yall!"[This message has been edited by WaterInYuhDish (edited 03-24-2022).]
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WalkerTexan
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MAR 23, 10:46 PM
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Yes, it sounds like you have the wires swapped on the sensor. The gauge uses an analog voltage to display temperature so the sensor is a resistor that varies with temperature. The indicator light uses a switch to engine return, commonly called ground. The switch is open until the engine is 250 degrees or so and then the switch closes to engine return. The light is likely on because you have it connected to the resistor which will allow current to flow. The gauge isn't working because it is connected to the switch and therefore no current is flowing to establish the analog voltage level. Here's how to check: disconnect the sensor and get a short piece of wire. Turn the key on and watch the dash while you momentarily connect one of the pins to the engine with the wire. If the gauge needle swings then that is the gauge wire; if the light comes on then that is the indicator wire. I suggest momentarily connecting because it isn't good to leave the gauge pegged. Now you know which wire is which so check the sensor with an Ohmmeter or DMM. The switch pin to engine should be open (infinite Ohms). The resistor pin to engine will read some value of Ohms based on temperature, I don't remember the table values but it is probably 2000 Ohms or less. Just make sure it isn't infinity. Once you know which is which, connect the switch to the light wire and resistor to the gauge. I would get you the wire colors but the PO may have changed some things so testing is more reliable. Or you could just swap and test but I prefer knowing rather than guessing. It's the engineer in me.
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WaterInYuhDish
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MAR 23, 11:05 PM
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| quote | Originally posted by WalkerTexan:
Yes, it sounds like you have the wires swapped on the sensor. The gauge uses an analog voltage to display temperature so the sensor is a resistor that varies with temperature. The indicator light uses a switch to engine return, commonly called ground. The switch is open until the engine is 250 degrees or so and then the switch closes to engine return. The light is likely on because you have it connected to the resistor which will allow current to flow. The gauge isn't working because it is connected to the switch and therefore no current is flowing to establish the analog voltage level. Here's how to check: disconnect the sensor and get a short piece of wire. Turn the key on and watch the dash while you momentarily connect one of the pins to the engine with the wire. If the gauge needle swings then that is the gauge wire; if the light comes on then that is the indicator wire. I suggest momentarily connecting because it isn't good to leave the gauge pegged. Now you know which wire is which so check the sensor with an Ohmmeter or DMM. The switch pin to engine should be open (infinite Ohms). The resistor pin to engine will read some value of Ohms based on temperature, I don't remember the table values but it is probably 2000 Ohms or less. Just make sure it isn't infinity. Once you know which is which, connect the switch to the light wire and resistor to the gauge. I would get you the wire colors but the PO may have changed some things so testing is more reliable. Or you could just swap and test but I prefer knowing rather than guessing. It's the engineer in me. |
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Thank you! I'll definitely test these tomorrow! Just to clarify, when you say disconnect the sensor, you mean the connector, not the sensor that's bolted into the engine, correct? If this all pans out and the sensor is working it should be as simple as resplicing the connector and flipping the wires, yes? I'll update this when I can. Thanks again!
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WalkerTexan
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MAR 24, 12:13 AM
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Yes, disconnect the connector from the sensor. Leave the sensor in place so it is grounded. That allows you to test it as I described.
If it is wrong as I suspect then you can resplice the connector so that the wires are correct.[This message has been edited by WalkerTexan (edited 03-24-2022).]
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MulletproofMonk
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MAR 24, 08:09 AM
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WaterInYuhDish
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MAR 31, 12:26 PM
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It did end up being wired backwards. All diagrams show that I spliced it in properly but maybe manufacturers of the sensors flipped which pin sends what signal. Thanks for the help everyone!
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WalkerTexan
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MAR 31, 10:29 PM
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WaterInYuhDish
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APR 01, 11:14 AM
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| quote | Originally posted by WalkerTexan:
Glad you got it fixed. |
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Me too! Thank you for your help. Once I got the wiring proper, I let it idle for about 20-30 minutes and the gauge went all the way to the red before the fan kicked on but with a laser gun for reading temps; the hoses, sensors and anything I could think of to shoot was cooler than what the dash gauge was showing. I've done some reading of different issues related but don't see any that quite fit mine. As of now, since everything is working to the extent that no damage is going to be done, I'm not too worried but am curious if anyone has any ideas for getting more accurate reading on the dash gauge.
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