[Fixed!] 1998 Nissan Frontier with KA24DE -- Temp Gauge
Can anyone guide me on how to test the sensor to see whether it's the sensor, the wire, or the gauge? I'd love to make this thing work correctly. The check engine light is also on, but I'd like to tackle the seemingly simpler problem first so I start with a win. Thanks,
Jim
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you can test it if you want, or do a cluster internal check for gauges. follow the instructions
part # 25080-89907
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I did the gauge check according the text you pasted and the temperature gauge reacted as depicted that it should in the service manual. The thermal transmitter is on order and it's supposed to be here Monday. I can report back then, Thanks for your help. Failing to understand this is driving me crazy.
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- Hardtopdr2
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- John Clark
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Why not unplug the connector to the sensor and see what happens on the gauge. Then short the wire to ground and see if there is any gauge change.
Also, that should be a 5v reference that is pulled to ground by the thermistor. This is chapter 6 in Paul's book. Unplugged it should have 5v on it that you can check with a meter or scope and then when plugged in the resistance in the thermistor is varied by the coolant temp. Once plugged in you should be able to backprobe and see what kind of voltage is showing on the wire. If it's somewhere between 0.5 and 4.5v then the sensor is probably good.
You'll also want to get a wiring diagram for the circuit. It's not uncommon to have more than one temp sensor...one for fans or PCM input and another for the gauge. You need to make sure you're on the right sensor.
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- John Clark
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In theory, if you unplug it and turn on the key, that would be high resistance, so low temperature should be indicated. If you short the wire to ground, that would be low resistance and high temperature. If the gauge sweeps properly but always reads full hot that tells me to look for either a shorted sensor or a shorted wire. If you unplug it and it still reads full hot then likely a shorted wire between the temp sensor and the gauge.
You can also do the ohm check of the sensor and make sure it matches the specs in the above post.
Also, it looks like the temp sensor that goes to the computer has two wires and the gauge sensor has one wire....again, assuming the 97 Pathfinder is similar.
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I haven't backprobed yet and I need to get the diagram back out and check the rest of the circuit. I'm not even sure if it's fused or not. Thanks guys! It's starting to make sense.
One more thing... after I changed the sensor and it randomly went hot again, I stopped and put the cluster in diagnostic mode. The gauge responded as it should have, even though in regular mode with the truck running, it was pegged hot. I don't know what that means.
But, since it will just quickly go all the way hot and then "fix itself", that really seems like it's shorting somewhere. I just have to find it.
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- John Clark
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Did you ohm check the sensor as described in the manual photo above?
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Someone mentioned this above already, but did you confirm that you don't have any air bubbles in the coolant? The level is full and you have good heat in the cabin? A lot of those have a small air vent plug on the intake manifold you can pull while filling. You then fill it until a steady flow of coolant flows out of the air vent, with no air bubbles, then put the plug back in and tighten it down.
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I turned KOEO before I started and really tugged on the harness all the way up to where it goes through the firewall and couldn't get the gauge to move.
I didn't check the air bubbles, but I did find the air valve. I'll bleed it first thing tomorrow afternoon when I get home from work and the truck is cold.
I also think next I need to figure out where the Flexible Printed Circuit is that the sensor wire runs to. Anyone know if that is actually in the cluster? Thanks.
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- Hardtopdr2
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it would be helpful to use a scan tool to watch the coolant temp that is being sent to the PCM during your drives and compare to what the gauge is telling you.
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I back out of the driveway into the street. At that time, the gauge pegs hot. Great! That's what I need! I pop the hood and jump out and disconnect the gauge. Gauge goes cold when disconnected. Oops. Not what I was expecting. Plug it back in, gauge goes hot. Dang. Pull back in driveway and run to get my meter to ohm the sensor, but then it went back to normal. Crud. But, the evidence suggests that my gauge may actually be functioning. Kind of embarassing.
I like the scan tool idea. I have a friend with a scan tool and I'm going to try it. It's a snapon Modis. We tried it a while back and it said it could not communicate with the truck. But, it will read in generic obd mode. I don't know why that is. I'll see if it can read the sensors in generic mode. Thanks for the idea.
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