temp gauge not working

[02firebird]

I turn on my car and the gauge is working just fine, got up to temp and everything. However, about 30 min later I look down and its reading 0, but about 10 min after that it started working again, so I'm confused. Another thing, when the gauge wasn't working it sounded like the fan was running constantly, and as soon as at started working again the fan stopped. Any ideas?

[rod knock]

Re: temp gauge not working

On my 02 that was the default mode for a bad thermostat, my thermostat was stuck wide open so the car took too long to get up to normal operating temperature.

The computer doesn't get a correct temperature reading so it goes into safety mode by turning on both fans..

[ssms5411]

Re: temp gauge not working

I would check your coolant temp harness to see if its shorting , other than that check the sensor to make sure its still good.

[02firebird]

Re: temp gauge not working

I'll do that tomorrow in the daylight and let you know what I find.

[ssms5411]

Re: temp gauge not working

You should get .5 volts from the sensor when plugged in.

[rod knock]

Re: temp gauge not working

If the motor doesn't heat up properly after a few running cycles, it will shut off the temp gauge and turn the fans on.

It's similar to limp mode in the FI system, when the computer senses a problem it goes into safe mode, in this case that's both fans on and no temp gauge.

The most common reason for a car taking too long to warm up is a thermostat that's stuck open, that's assuming some one hasn't wired the fans to run all the time or some thing like that.

[rod knock]

Re: temp gauge not working

Im not positive but if the coolant temperature sending unit goes bad I believe you would get a check engine light.

[transamtom1]

Re: temp gauge not working

Hib Halverson just did a write up on this,a cooler thermo or a bigger rad can also cause this as the computer does not see the engine warming up quick enough.

[02firebird]

Re: temp gauge not working

I replaced the sensor and everything looks good to go. Thanks for all the help.

[rod knock]

Re: temp gauge not working

If you didnt have a check engine light on, you may have the same issue in a few days.

[landj]

Re: temp gauge not working

sounds like a bad sensor or short to me too. Intermittant electrical problems are the worst. You have to diagnose them when they on the fritz or visually inspect the whole circuit (follow the wire and look for breaks, cracks, shorts etc). Connections could be corroded too, so disconnecting connectors and cleaning them up may help if the new sensor doesn't do it for you. I would *think* a wide open thermostat would just read cool. I've never seen a wide open thermostat jump from normal temperatures to 0 in my short lived shade tree mechanic experience. If it was stuck wide open, it would just take forever to warm up. That the fans are kicking on indicates to me that it is a sensor and not a guage problem.

The reason the fans kick on is because the computer is sensing a fault (like 0 volts or ground) and is kicking them on to be safe.

[rod knock]

Re: temp gauge not working

sounds like a bad sensor or short to me too. Intermittant electrical problems are the worst. You have to diagnose them when they on the fritz or visually inspect the whole circuit (follow the wire and look for breaks, cracks, shorts etc). Connections could be corroded too, so disconnecting connectors and cleaning them up may help if the new sensor doesn't do it for you. I would *think* a wide open thermostat would just read cool. I've never seen a wide open thermostat jump from normal temperatures to 0 in my short lived shade tree mechanic experience. If it was stuck wide open, it would just take forever to warm up. That the fans are kicking on indicates to me that it is a sensor and not a guage problem.

The reason the fans kick on is because the computer is sensing a fault (like 0 volts or ground) and is kicking them on to be safe.

The computer reads the temperature, if after a certain amount of time the temp isnt where it should be, it goes into a kind of safe mode, it turns the gauge off and turns both fans on.

[landj]

Re: temp gauge not working

The computer reads the temperature, if after a certain amount of time the temp isnt where it should be, it goes into a kind of safe mode, it turns the gauge off and turns both fans on.

I learn something new everyday. Thanks!

[rod knock]

Re: temp gauge not working

I learn something new everyday. Thanks!

It will do the same thing with a bad coolant temperature sending unit but that will almost always give you a check engine light.