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This is on a 98 Camaro. My coolant temp gauge is not accurate. After about 5 minutes of running the gauge will go from the lowest setting to almost showing 260 degrees.
I plugged the obd scanner in after the temp gauge was reaching 210 degrees. It read about 110 degrees, and went up to 117 degrees and varied 2 degrees up and down.
I checked the ohms on the temp sensor (3 wire) after I shut the engine off and compared it to a chart and it was reading between 180 and 190 degrees, which would seem to be correct because my aftermarket fan controller is set to turn on at 180, and it cycles on and off.
I have tried 2 different brand new temp sensors that both did the same thing. I'm not really sure what to do now but I'm thinking it is some type of wiring issue?
The 98 cars ran directly to the dash and to the ecu. The newer cars received the readings from the ecu only and only had a 2 pin sensor.
So if your readings are not correct but the sensor is good it must be in the wiring, or a short in the dash
There is a write up on converting the gauges on 99+ cars to go to the dash directly, you could use that to back track your wiring
Thanks, I purchased a potentiometer and I'm going to wire it in line to see what's going on with the gauge.
In doing some research I found another member on here with a very similar problem, and he said that when he plugged his connectors for all of the AC system it fixed the problem. I have my ac disconnected right now.
If the gauge is off is there any way to adjust the needle? While I was working on the car I had the sensor unplugged and it spent a lot of time maxed out so I'm wondering if that has caused it to be not accurate, which is why I got the pot to see exactly what it shows at any temp I set it at.
You can removed the needle on the dash, leave the cover off of it, start the car and then put the needle back on where you want it.
That it my primary fear when purchasing an body, some one would do that with the oil pressure reading
Well I tried to hook the pot up and everything is working in reverse. The higher the ohms the higher the temperature on the gauge. I tried switching the wires around but it did the same thing. I'm not a wiring expert so maybe someone can help with that.
While I had the pot on, I got the gauge to read the 3/4 line and as I was watching it I noticed the gauge dropped a bit and a few seconds later it rose back up. I'm using a different ground with the pot so I know it's not a wiring issue unless something else in the gauge cluster is affecting it
What reading on the dash does the car show when you turn the key to the run position with the engine turned off and the sensor in plugged.
The sensor itself has a spring inside of it that expands as it gets hotter which grounds the voltage through the sensor. So as it gets hotter the spring expands and the gauge rises.
With the Hondas, they had a single wire sensor, so I've never had to play with the fbody sensor, but it should work on the same principle. The sensor should send voltage back to the dash based on the resistance of the sensor
What reading on the dash does the car show when you turn the key to the run position with the engine turned off and the sensor in plugged.
The sensor itself has a spring inside of it that expands as it gets hotter which grounds the voltage through the sensor. So as it gets hotter the spring expands and the gauge rises.
With the Hondas, they had a single wire sensor, so I've never had to play with the fbody sensor, but it should work on the same principle. The sensor should send voltage back to the dash based on the resistance of the sensor
If it's unplugged with key on the gauge stays at 0.
How does the sensor make a voltage? I thought it was more like the pot I'm using just increasing the resistance.
I tried plugging the AC stuff in and it made no difference. When the engine is warming up I can watch the gauge go from 0 to the red zone in less than 5 minutes of just idling, and the thermostat hasn't even opened up.
I never had a problem with the gauge before my engine swap and I'm using the same gauge, wiring, and sender. I replaced the sender but it's still doing the same thing
Quick question, when the engine is cold remove the radiator cap, and then disconnect the steam tube from where it meets under the throttle body. Does coolant come out of that hole?
If you drained the entire system and connected all of the hoses, and then filled your coolant, your engine is filled with air and will get hot almost instantly while the hoses and radiator stay cold. When you fill the car with coolant you need to leave that cross over hose un plugged in order for the coolant to go into the engine
So are your hoses hot to the touch when your needle goes to hot, or is only your engine hot
Quick question, when the engine is cold remove the radiator cap, and then disconnect the steam tube from where it meets under the throttle body. Does coolant come out of that hole?
If you drained the entire system and connected all of the hoses, and then filled your coolant, your engine is filled with air and will get hot almost instantly while the hoses and radiator stay cold. When you fill the car with coolant you need to leave that cross over hose un plugged in order for the coolant to go into the engine
So are your hoses hot to the touch when your needle goes to hot, or is only your engine hot
I have a sbc in the car and I'm running a lt1 rad so it doesn't have any type of steam lines.
I bled the coolant and I'm pretty positive that there is no air in the system. I thought about that and re-bled the system with no change.
I'm running an adapter for the sensor on the intake and I had a slight leak of coolant so I know there can't be any air trapped under the sensor.
Maybe I will try to move the sensor to a different location and see if anything changes at all
So let's get specific. It's time to get a laser temperature gun to make sure all your temperatures on the heads are within +/10 degrees of each other. I'd hate to assume the sensor is bad if the motor is actually over heating
You say small block Chevy, I'm assuming it's not the LS platform that requires the coolant steam tube fittings on the head
I love this picture because it illustrates how an air bubble can disrupt coolant flow, and trap hot coolant
Does your heater work? Have you verified the thermostat is opening by squeezing the hot hoses to make sure they are not rock hard, are the upper and lower hoses both hot to the touch
So let's get specific. It's time to get a laser temperature gun to make sure all your temperatures on the heads are within +/10 degrees of each other. I'd hate to assume the sensor is bad if the motor is actually over heating
You say small block Chevy, I'm assuming it's not the LS platform that requires the coolant steam tube fittings on the head
I love this picture because it illustrates how an air bubble can disrupt coolant flow, and trap hot coolant
Does your heater work? Have you verified the thermostat is opening by squeezing the hot hoses to make sure they are not rock hard, are the upper and lower hoses both hot to the touch
I do have a temp gun, the thermostat housing stays at around 180 and the rad is usually around 170.
Thermostat is definitely opening.
I currently have my heater core disconnected so I can't verify if I have heat.
I'm using a spill free funnel to get the air out of the system I have the funnel a good 10" above the highest part of the coolant system.
I haven't had a chance to run my other temp gauge yet
Put my mechanical water temp gauge on the car, I changed absolutely nothing and it never saw above 180 degrees. Once the thermostat opened the temp would go down to 160 then creep back to to 180 and repeat the process.
I don't think the actual gauge is broken because it worked fine before.
07-14-2017, 03:28 PM
Coolant temp gauge not accurate 
