Temp Gauge Fluctuates
02-19-2018, 05:12 PM
#1
Thread Starter
Join Date: Feb 2017
Location: PA
Posts: 2
Temp Gauge Fluctuates
Details
2007 Mustang V6 4.0L 5-Spd Manual with 108K miles
Temp gauge fluctuates. Doesnt matter if your sitting idle or driving down the road. When you start the car it warms up and the gauge rises to almost half way between C and H. Normally the gauge would stay at this point while the vehicle is running. Lately I have noticed that it will start dropping and then rise again and drop again and rise again. Sometimes dropping as far as C and then rise again to about the half way point. It never goes past its normal operating temp point on the gauge.
In December 2017, I was at my dealership for a state inspection and I had mentioned this to them when I dropped it off. I spoke to the mechanic and he said he never heard of such a thing and was not able to duplicate the problem. As soon as I left it was doing it so i guess he never fully investigated.
The heater blows hot air. So that rules out air in the system.
The engine does not overheat, at least as far as I can tell by the temp gauge.
Is it a defective thermostat or a engine coolant temp sensor. I would think if the sensor were bad, I would see a service engine soon light.
2007 Mustang V6 4.0L 5-Spd Manual with 108K miles
Temp gauge fluctuates. Doesnt matter if your sitting idle or driving down the road. When you start the car it warms up and the gauge rises to almost half way between C and H. Normally the gauge would stay at this point while the vehicle is running. Lately I have noticed that it will start dropping and then rise again and drop again and rise again. Sometimes dropping as far as C and then rise again to about the half way point. It never goes past its normal operating temp point on the gauge.
In December 2017, I was at my dealership for a state inspection and I had mentioned this to them when I dropped it off. I spoke to the mechanic and he said he never heard of such a thing and was not able to duplicate the problem. As soon as I left it was doing it so i guess he never fully investigated.
The heater blows hot air. So that rules out air in the system.
The engine does not overheat, at least as far as I can tell by the temp gauge.
Is it a defective thermostat or a engine coolant temp sensor. I would think if the sensor were bad, I would see a service engine soon light.
02-23-2018, 12:40 AM
#2
Banned
Join Date: Jan 2018
Location: Pennsylvania
Posts: 2,327
It's usually the stepper motors in the clusters that go bad. They have
kits on eBay that come with 4 or 6 motors, solder, and soldering iron.
They tell you that you have to replace the cluster, and that is not so.
You can, but that's not 100% true.
kits on eBay that come with 4 or 6 motors, solder, and soldering iron.
They tell you that you have to replace the cluster, and that is not so.
You can, but that's not 100% true.
02-23-2018, 11:06 AM
#4
4th Gear Member
Join Date: Nov 2009
Location: SoCal
Posts: 1,826
If you have access to a handheld tuner or other such device capable of viewing real time OBD parameters, it would be interesting to see what the PCM "thinks" engine temperature is doing while at the same time monitoring the gauge.
If OBD readings reflect gauge readings then I would suspect a faulty sending unit. If OBD reading shows a steady engine temp but the gauge is all over the place then as others suggested the issue is probably in the cluster.
If OBD readings reflect gauge readings then I would suspect a faulty sending unit. If OBD reading shows a steady engine temp but the gauge is all over the place then as others suggested the issue is probably in the cluster.
02-27-2018, 11:39 AM
#5
Thread Starter
Join Date: Feb 2017
Location: PA
Posts: 2
Thank you to all who replied.
I did resolve the problem and wanted to post my solution. I looked at one more thing before deciding what route to pursue. So after driving the car to warm up the engine, I turned the ignition key to the on position, but did not start the engine. I observed that the temp gauge rose to the half way point(normal operating temp) and then begin to fluctuate. This told me it was an electrical issue.
So I replaced the engine coolant temperature sensor and this fixed my problem.
I did resolve the problem and wanted to post my solution. I looked at one more thing before deciding what route to pursue. So after driving the car to warm up the engine, I turned the ignition key to the on position, but did not start the engine. I observed that the temp gauge rose to the half way point(normal operating temp) and then begin to fluctuate. This told me it was an electrical issue.
So I replaced the engine coolant temperature sensor and this fixed my problem.
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