2005 Mustang GT Temp Gauge pegged at 0 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-17-2009, 05:24 AM
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2005 Mustang GT Temp Gauge pegged at 0

I few weeks ago I noticed that the temp gauge on my 2005 Mustang GT 4.6L was sometimes stilled pegged at the low end after several miles of driving, but the car seemed to be at normal temp. When I shut down and restarted the warm car in the parking lot, the gauge popped up to normal mid range.
I also had problems with my tach yesterday, where it seemed to find a zero point at about 4500 rpm. It still worked, but at driving speed the needle pointed almost straight down.

I fixed the tach problem by disconnecting the battery, cleaning the terminals, and reconnecting the battery. But this did not fix the temp gauge problem. The gauge still reads zero most of the time, and it is more frequent now that the weather is colder.

It seems like my gauge cluster is either not "booting" correctly (the process where the needles flip back and forth from max to zero) when I start the car, or there is some loose connection that affecting the temp gauge initialization.

Any ideas on where to start troubleshooting? The car is out of warranty, and I don't have the budget to buy a new gauge cluster. I can try swapping temp sensors, but I'm not sure that is the source of the problem.

Thanks,

Bruce

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Old 12-21-2009, 01:54 PM
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A new temp sensor is cheaper than a gauge cluster. If you change the sensor and it fixes the problem, then it's done. If it doesn't , then at least you know the sensor is not the problem. Sometimes it's fixing things by replacing the cheapest parts first, process of elimination.
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Old 12-22-2009, 05:08 PM
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The temp sensor will be a good place to start, but I don't think the problem will end there.

I found another link on the net where someone explained that all the gauges use small stepper motors to move the needle, and sometimes they get a little weak, or slow to react. The article said it is possible to replace the stepper motor on one gauge, but you have to remove the cluster, then the gauge needle, and finally replace the motor.

I'm going to recheck all the connections first, then make sure everything is dry around the junction boxes, and then look at replacing the sending unit. I hope that will resolve the problem.

Pulling the gauge cluster for repair or replacement will definitely be a last resort. Complete replacement is a dealer-only task, since the mechanic has to download the data from the old cluster, and then transfer it to the new one.

Bruce
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Old 12-27-2009, 07:18 PM
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Got another tidbit of information for those who are Mustang fans.

-- The 2005 Mustang GT (4.6L V8) does not have a coolant temperature sensor!!
(although the V6 does have one)

This engine in the 2005 GT has a cylinder head temperature sensor, and there is an algorithm in the computer that calculates engine temp based on head temp. This is considered more reliable, since it works even if there is no water in the cooling system.

Bruce
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Old 03-28-2010, 05:11 PM
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I have a follow-up to my own post about gauge problems on my 2005 Mustang GT.

I ordered upgraded gauge stepper motors from a guy on Ebay, and six of them cost me $48 with shipping. I took apart the cluster, unsoldered the motors and replaced all of them. I was being very careful, so it took me about 3 hours, but I could go faster now that I understand how it all comes apart. To compare prices, a new cluster would have been $350-450, plus programming by the dealer to move my mileage and configuration data over to the new cluster.

So far it looks like everything is working fine, but I haven't had a cold day yet (that was when it usually stuck).

By the way, the defective gauge stepper motor problem applies to the 2005 Mustangs only, but there are also several GM models that have exactly the same problem. Just do a search on Ebay for stepper motor and look through all the years and models that may need the fix.

Bruce
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Old 03-28-2010, 05:18 PM
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Quote:
Originally Posted by 75gmck25
I have a follow-up to my own post about gauge problems on my 2005 Mustang GT.

I ordered upgraded gauge stepper motors from a guy on Ebay, and six of them cost me $48 with shipping. I took apart the cluster, unsoldered the motors and replaced all of them. I was being very careful, so it took me about 3 hours, but I could go faster now that I understand how it all comes apart. To compare prices, a new cluster would have been $350-450, plus programming by the dealer to move my mileage and configuration data over to the new cluster.

So far it looks like everything is working fine, but I haven't had a cold day yet (that was when it usually stuck).

By the way, the defective gauge stepper motor problem applies to the 2005 Mustangs only, but there are also several GM models that have exactly the same problem. Just do a search on Ebay for stepper motor and look through all the years and models that may need the fix.

Bruce
Kudos for following up on your thread! I'm sure this will be more than helpful for someone with a similar problem in the future.
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