Erratic temp gauge
Thread Starter
Intermediate
Joined: Jul 2006
Posts: 41
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From: Gatineau QC
Erratic temp gauge
I've recently noticed that my temp gauge goes crazy sometimes. I'm driving along at normal temperatures (around 190) and then it'll start moving erraticly, but then it'll go back to 190 for a couple seconds and then start moving crazily again. This mostly happens on the highway. Is it possible that the temperature sensor starts freaking out when I reach 195 or 200 but acts normally at colder temperatures?
Please let me know if you've had that problem or know how I can troubleshoot and fix this.
Type slowly, I'm a noob.
Please let me know if you've had that problem or know how I can troubleshoot and fix this.
Type slowly, I'm a noob.
Pro
Joined: Sep 2002
Posts: 620
Likes: 2
From: San Antonio TX
Originally Posted by CrypTECH
I've recently noticed that my temp gauge goes crazy sometimes. I'm driving along at normal temperatures (around 190) and then it'll start moving erraticly, but then it'll go back to 190 for a couple seconds and then start moving crazily again. This mostly happens on the highway. Is it possible that the temperature sensor starts freaking out when I reach 195 or 200 but acts normally at colder temperatures?
In my situation, I had installed a steel mesh cover over my upper radiator hose. This mesh would sometimes make contact with the top of the temperature sending unit where the wire is connected. It caused the same symptoms as you are describing.
Instructor
Joined: Jan 2005
Posts: 239
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From: Waterford MI
I had the same issue, and approached it the same way that cchristo did.
Ended up being the connector to the temp sensor itself was barely making contact.
Got a fresh connector, crimped it on, no more problem.
Ended up being the connector to the temp sensor itself was barely making contact.
Got a fresh connector, crimped it on, no more problem.
Thread Starter
Intermediate
Joined: Jul 2006
Posts: 41
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From: Gatineau QC
Thanks, I'll go check for bad contacts.
I wasn't sure where that sensor was located (I wasn't kidding about being a noob), I guess I'll be looking in the vicinity of the upper radiator hose.
I'll let you know what I find...
I wasn't sure where that sensor was located (I wasn't kidding about being a noob), I guess I'll be looking in the vicinity of the upper radiator hose.
I'll let you know what I find...
Thread Starter
Intermediate
Joined: Jul 2006
Posts: 41
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From: Gatineau QC
I'm pretty sure I've located it: a green wire. The wire looks old and a bit dry but I don't see any obvious problems with it or anything. I unplugged and replugged and tried to make sure it's not touching anything else, but it still went a little crazy on the drive home tonight, although a little less than usual.
I'll keep trying to debug this and I'll let you know when I get it.
Thanks for the help
I'll keep trying to debug this and I'll let you know when I get it.
Thanks for the help
Pro
Joined: Sep 2002
Posts: 620
Likes: 2
From: San Antonio TX
Originally Posted by CrypTECH
I'm pretty sure I've located it: a green wire. The wire looks old and a bit dry but I don't see any obvious problems with it or anything. I unplugged and replugged and tried to make sure it's not touching anything else, but it still went a little crazy on the drive home tonight, although a little less than usual.
I'll keep trying to debug this and I'll let you know when I get it.
Thanks for the help
I'll keep trying to debug this and I'll let you know when I get it.
Thanks for the help
Disconnect the temp sensor wire from the sensor. Put the multimeter switch to the Ohm setting. With the car running, put one probe on the sensor terminal and the other to ground. The needle should begin to move as the water begins to heat up. It should be a smooth movement, with some variation as the thermostat opens and closes. If it checks out, you have pretty much ruled out the temp sensor as the problem. Make sure you wiggle the terminal on the sensor occasionally, in case it's damaged.
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Pro
Joined: Sep 2002
Posts: 620
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From: San Antonio TX
Originally Posted by CrypTECH
I've got a multimeter so I can try that but I doubt I'll see the problem while the engine is idling. The gauge only goes crazy the temperature goes close to 200.
When you say the needle is erratic, is it almost violently erratic, or is it just moving back and forth? If it's a short, the needle will almost snap back and forth. If it's actually something like an air bubble in the cooling system, it would be much more gradual.
You'll want to use the multimeter to check the wire for shorts as well. Make sure that you are moving the wire around all along it's length while you are doing it.
I'm trying to keep you from having to go into the gauge cluster! That's when it will become a much bigger PIA!
Thread Starter
Intermediate
Joined: Jul 2006
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From: Gatineau QC
Yeah, it goes violently crazy.
Ok, I'll try the multimeter for sure.
If I have to go in the instrument cluster, so be it, it'll give me a chance to clean things up a bit and maybe fix the clock while I'm at it.
Ok, I'll try the multimeter for sure.
If I have to go in the instrument cluster, so be it, it'll give me a chance to clean things up a bit and maybe fix the clock while I'm at it.
Pro
Joined: Sep 2002
Posts: 620
Likes: 2
From: San Antonio TX
Originally Posted by CrypTECH
Yeah, it goes violently crazy.
Ok, I'll try the multimeter for sure.
If I have to go in the instrument cluster, so be it, it'll give me a chance to clean things up a bit and maybe fix the clock while I'm at it.
Ok, I'll try the multimeter for sure.
If I have to go in the instrument cluster, so be it, it'll give me a chance to clean things up a bit and maybe fix the clock while I'm at it.
Unless your gauge is actually bad (unlikely), and the under hood wiring is good, and you've checked and cleaned the connectors at the firewall, you are most likely going to find the problem is with the Printed Circuit board that supplies signal to the gauges. These things are pretty crappy pieces of work and don't stand up well to repeated tampering. They aint cheap either, for what they are.
Good luck with the clock! I managed to get mine working for a day or two, then it went back to showing the correct time only twice a day.
My stereo has a clock anyway, so I'm probably going to put a transmission temp gauge in place of the clock.
Last edited by cchristo; Sep 7, 2006 at 12:48 PM.
