The temperature gauge goes up when you turn on the lights

Luis911 · Apr 21, 2010

When you turn on the lights, temperature gauge goes up 1 1/2 level, this is normal?.
The car gets very hot after 20 minutes, and was changed 2 times the thermostat at this time is no thermostat and gets very hot; with the engine cold and running, took off the radiator cap and water flow (I guess the water pump works).
With the engine running, the car accelerates and the fan clucth also speeds.
Tests are simple, other tests I have to do?

MustangLX-5.0 · Apr 21, 2010

That's not a cooling issue. That's an electrical problem, most likely a bad ground some place. My V6 does the same thing. Replacing the sender or gauge wont fix it. Perhaps look around and find all ground terminals that are attached via a small bolt. Remove and clean corrosion off then re-attach. You will have to probably clean a lot of them to find out which one the gauge cluster grounds off at. I don't know where it's at. Perhaps someone else knows the location.

Chances are the gauge moves up if you turn other electrical loads on (eg.. step on the brake pedal, rear defrost etc). The bad ground is affecting the circuit reading. It could be that, or something else has a bad ground and is drawing more juice out of the cluster circuit.

89stangGT · Apr 21, 2010

I had a similar situation, when I shut the car off with the lights ON, the temp gauge would peg hot. Obviously the engine is not getting hot since it is off so it is an electrical issue. I found that the ground between the engine block and the firewall was disconnected.

I would check that first. It is located (I think) behind the engine on the driver's side head.

Cobra1741 · Apr 21, 2010

yea dont worry about it, it does it on mine too.

Shaolin Crane · Apr 21, 2010

im having similar issues let me know if you fix it

$uperstang · Apr 21, 2010

it's normal for these damn cars mine's been doing it for 16 years

Luis911 · Apr 22, 2010

MustangLX-5.0 said:
That's not a cooling issue. That's an electrical problem, most likely a bad ground some place. My V6 does the same thing. Replacing the sender or gauge wont fix it. Perhaps look around and find all ground terminals that are attached via a small bolt. Remove and clean corrosion off then re-attach. You will have to probably clean a lot of them to find out which one the gauge cluster grounds off at. I don't know where it's at. Perhaps someone else knows the location.

Chances are the gauge moves up if you turn other electrical loads on (eg.. step on the brake pedal, rear defrost etc). The bad ground is affecting the circuit reading. It could be that, or something else has a bad ground and is drawing more juice out of the cluster circuit.

Apparently I have two problems , one electric and one
temperature, because the car overheats

MustangLX-5.0 · Apr 22, 2010

I can tell you this, turning your lights on WON'T cause your engine to overheat. Ignore the gauge problem for now. Check to make sure you have sufficient coolant in the radiator and the reservoir. How do you know it overheats? What are the symptoms? Is it steaming or spilling coolant? Does it do this while idling for a long time or while you're driving around? If you have enough coolant, and it does it while you're driving, it could be the fan clutch. The fan can still be spinning and the engine could still overheat because it may not spin fast enough. Or it could be the front lower air dam (or air diverter). That is the lower black plastic thing on the very bottom side of the front bumper cover. It's the thing most people end up scraping while parking too close to a parking block. If that is missing or bent up, then you can easily overheat while driving. If you are overheating while sitting idle, then it could be.. again, a bad fan clutch. Or it may be that the engine is running way too lean or way too advanced in timing. Last but not least, a blown head gasket. But lets rule out other possibilities first.

Luis911 · Apr 22, 2010

MustangLX-5.0 said:
I can tell you this, turning your lights on WON'T cause your engine to overheat. Ignore the gauge problem for now. Check to make sure you have sufficient coolant in the radiator and the reservoir. How do you know it overheats? What are the symptoms? Is it steaming or spilling coolant? Does it do this while idling for a long time or while you're driving around? If you have enough coolant, and it does it while you're driving, it could be the fan clutch. The fan can still be spinning and the engine could still overheat because it may not spin fast enough. Or it could be the front lower air dam (or air diverter). That is the lower black plastic thing on the very bottom side of the front bumper cover. It's the thing most people end up scraping while parking too close to a parking block. If that is missing or bent up, then you can easily overheat while driving. If you are overheating while sitting idle, then it could be.. again, a bad fan clutch. Or it may be that the engine is running way too lean or way too advanced in timing. Last but not least, a blown head gasket. But lets rule out other possibilities first.

I realize that there is overheating when the car loses power and there is blue smoke, last week the indicator reached the upper limit and the car did not want to move forward, it's like when you no longer have gas, waited an hour to lower the temperature, and after the car ran.
Have enough antifreeze and the loss is minimal.
When I go on the highway the temperature is maintained at half the rate, but at idle the temperature begins to rise and it does not drop until the car is on the highway.

a month ago the timing was 14 degrees and put it at 10 degrees, I think from there I have noticed an increase in temperature.

is probably the fan clutch as you said, is there any way to make a test, all I did is to see if it turns at idle and accelerating the car and apparently looks good.

The temperature gauge goes up when you turn on the lights

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