Temp gauge reads cold - 1994 Accord

#1 (**permalink**) 08-12-2005, 09:05 PM

1994 Accord EX
Car starts and runs OK, but mileage is a bit low. I think the O2 sensor
may be shot - barely passed smog last couple times. But new issue:
My temp gauge rarely rises above the bottom peg.
Checked the TW sensor with an ohmeter and IR gun. The resistance
appears very close to the published curve for Standard TS172:
degF/ohms: 66/6700, 93/2000, 120/1000, 180/420.
Temp gauge is not off the bottom peg at 180 degF; if driven awhile it
can get hotter and gauge makes a slight movement.
Test: Shorting the sensor wire to ground pegs the meter (300 mA).
Substituting a 67 ohm resistor, the gauge reads about 1/3 scale (below
the center mark; 112 mA). With a 150 ohm resistor (60 mA) the meter
barely moves.
Seems as if the meter, or the metering circuit, may be faulty rather
than the temp sensor.
Anyone have experience with this type of failure? Could bad temp
circuit affect smog?
... acellier

--
acellier

#2 (**permalink**) 08-12-2005, 10:34 PM

>> My temp gauge rarely rises above the bottom peg. Checked the TW sensor
with an ohmeter and IR gun. The resistance appears very close to the
published curve for Standard TS172: degF/ohms: 66/6700, 93/2000, 120/1000,
180/420. Temp gauge is not off the bottom peg at 180 degF; if driven awhile
it can get hotter and gauge makes a slight movement. Test: Shorting the
sensor wire to ground pegs the meter (300 mA). Substituting a 67 ohm
resistor, the gauge reads about 1/3 scale (below
> the center mark; 112 mA). With a 150 ohm resistor (60 mA) the meter barely
moves. Seems as if the meter, or the metering circuit, may be faulty rather
than the temp sensor. Anyone have experience with this type of failure?
Could bad temp circuit affect smog?<<

Sounds like your thermostat is stuck open, thus not permitting the engine to
warm up.

#3 (**permalink**) 08-12-2005, 10:34 PM

acellier wrote:
> 1994 Accord EX
> Car starts and runs OK, but mileage is a bit low. I think the O2 sensor
> may be shot - barely passed smog last couple times. But new issue:
> My temp gauge rarely rises above the bottom peg.
> Checked the TW sensor with an ohmeter and IR gun. The resistance
> appears very close to the published curve for Standard TS172:
> degF/ohms: 66/6700, 93/2000, 120/1000, 180/420.
> Temp gauge is not off the bottom peg at 180 degF; if driven awhile it
> can get hotter and gauge makes a slight movement.
> Test: Shorting the sensor wire to ground pegs the meter (300 mA).
> Substituting a 67 ohm resistor, the gauge reads about 1/3 scale (below
> the center mark; 112 mA). With a 150 ohm resistor (60 mA) the meter
> barely moves.
> Seems as if the meter, or the metering circuit, may be faulty rather
> than the temp sensor.

the gauge is very non-linear - stops people worrying about minute
variations.

> Anyone have experience with this type of failure? Could bad temp
> circuit affect smog?

bad thermostats affect smog. big time. sounds like yours is stuck
open. replace with oem, & don't forget the rubber gasket - they tend to
deteriorate too.

> .. acellier
>
>