Chasmag

Hello all. I have a 1999 V6 35th Mustang the I purchased about 3 months ago.

I have noticed the temp gage only goes to the same spot no matter how cool or how hot the engine is.

Can somebody tell me what to check or replace to correct this?

Thanks

jgsmuzzy

Message removed as I wasn't sure what I was talking about, SORRY

Cajunsix

First off, welcome on board .You're saying that when you start the car after it's been sitting overnight and the motor is cold, that the temp gage is the same as when it warms up, right? Well the usual suspects would be the temp sensor or the gage itself. You can see what the temp sensor is doing by putting your odometer into diagnostic mode. If you don't know how this is done, just put it in a reply and I'll be happy to explain. But back to the point, start the car while the odometer is on temp, as this should display the temperature in degrees celsius, and watch it for a few minutes as the car warms up. If the engine is warm and the reading hasn't changed, then you probably have a sensor related problem. If the reading is changing as it should, i.e. temp going up when the engine gets warmer and going down when the fan kicks on, then it's probably a gage related problem.

Chasmag

Excellant. How do I put it in Diagnostic mode? Didn't know there was one.

Cajunsix

Yeah, on 99+ mustangs there's a test or diagnostic mode, and it's pretty cool. You can access your computers actual readings on a lot of things. Your gages are made to smooth things out and not give a perfect reading. You can check your actual speed, as the speedo gage reads about 2 mph faster than you're actually going, in both english and metric, a digital tach, fuel, voltometer, etc. and even get a few trouble codes this way. Anyway, enough BS and straight to the point. To enter the test mode, place your key in the ignition. (A word before you do this, this will reset your tripodometer if you're keeping tract of mpg or such)Press and hold the trip odometer reset button. Without letting go, turn your key forward to the accessory mode, or as far as it will go without starting it. Wait for the odometer to display "test" and then release the button. All the gages should go all the way to one end, and then back down. You may start your car now. Now you can push the odometer button to toggle modes. One of the first few you'll pass up should say BulB (everything is in bad calculator looking letters), and all your bulbs in your gage cluster will light up. Through the next few times you push the button you'll see a few gibberish codes and stuff, a display of ENG000.0, which is a digital speedometer B) , then you'll see M 000.0, which is a metric speedo, then you'll see (not in order) fuel, tach (digital tachometer), volt I think, and then Oil. After OIL you should see (in bad calculator letters) deGCxxxx, with xxxx's being numbers. The xxxx's should display your engine temperture in degrees celcius. However, I don't believe that the temperature gage goes down very far, so your display may read 64 degrees C even though it's only like 25 C outside and your engine is cold. But when your engine starts warming up it should start to change after a few minutes idling or driving. The last post I did should fill in from here. Good luck with the gage problem and have fun playing around in test mode. I think I used my digital speedo for like a week when I discovered this. Oh, yeah, almost forgot.... to leave the test mode and return back to your odometer, just hold down the button till it changes or it will simply revert back when you turn your car off and back on.

Chasmag

Thanks. I will test it today. This kind of help is great.

Chasmag

B) Well been playing with this for a few days now. Found two interesting things. The temp in dianostic mode only goes to 92 degrees. The most interesting thing I did find is the oil pressure is at 0. Yep, zero. I know this is not correct becuase the oil gauge does work or I have one heck of a v6 that runs on no oil pressure. I will be looking for a wiring problem under the hood. If anybody has has this problem in the past please let me know what you found. If you have any ideas where to look for a problem please feel free to give me your ideas.

Thanks guys.

Cajunsix

Well, that sounds pretty normal, I think. 92 degrees (Celsius) is about where my fan and thermostat kick in so that sounds good for your temp gage. That means your cooling system is working well and your PCM is keeping the temp where it likes it. I forgot to mention that the OIL reading isn't an actual pressure reading. I forgot exactly what it is, but a value between 0 and 8 I think is normal. It's really more of a dummy gage than anything else. Fuel reading is 0 to 255, and low fuel light kicks on about 55, if I remember right. I don't remember alot of the readings off hand.

jgsmuzzy

Does it measur 0-60?????

I am going to have fun with that diagnostic mode, Digital speedo, YAY

:drive:

EDIT : Just been out, that is a great tool! Mine showed a 2mph difference. Means that I can drive at 82 on the speedo now and not get done!

Thanks for pointing out the diagnostic mode!