temp reading becomes higher after replacing temp sending unit

**mantoy** · November 10th, 2004 03:03 PM

my car's old temp sending unit was replaced because it's already worn out . what i noticed is the temp gauge reading becomes higher after replacing the sensing unit with a new one. almost 3/4 (a little above the halfway mark) ang normal reading.

before when i was using the old temp sending unit ang normal reading ng temp gauge is just 1/4 (a little below the halfway mark).

di naman masyadong mainit engine ko pag binuksan ko hood. di naman nababawasan coolant/tubig sa radiator. my water pump was just replaced 3 mos ago. wala ring leak sa mga hose.

temp gauge na ba problem ko? or the replacement part that i got sends inaccurate reading?

**Field Master** · November 10th, 2004 03:18 PM

How do you know that your temp gauge is worn-out? What was your indicator?
I encountered the same before (2nd hand pajero), dash is registering very low temp, about 1/4 just like yours. At first I was impressed kala ko ganoon ka efficient ang cooling system ng pajero. But I doubt if it is giving me an accurate read-outs kasi when i compared this to other pajero I could single out my ride as OUTLIER, namumukod tangi. What I did was to borrow my friend water coolant sensor at nilipat ko sa car ko only to find-out na tumaas nga ang reading. That's the time I decided to buy.
Kung halfway mark ok lang yun and this time less yun risk mo of running with overheat engine without you knowing it. Subikan mo maghanap nung katulad mo ng ride then isolate mo yun sensor.

**mantoy** · November 10th, 2004 03:37 PM

i had to replace the old temp sending unit kasi grounded na and erratic na ang reading. nasa redline sya pag tumatakbo ka pero pag naka-idle ka a little above C lang ang mark which is so weird. its normal reading used to be 1/4 (a little below halfway mark)

the problem with my new temp sending unit eh sobrang taas naman ang normal reading nya. lagpas na sa halfway mark (3/4) which i think is also not correct kasi di naman ganun kainit engine ko.

my ride nga pala is '89 corolla.

**Ungas** · November 10th, 2004 04:09 PM

When was the last time you changed water and coolant mixture? What ratio is your mix? Or you may need annual radiator cleaning/flushing?

**Field Master** · November 10th, 2004 04:43 PM

The temp sensor is a variable-resistance sensor. To check the coolant-temperature sensor yourself, use a VOM -- or digital volt/ohm meter. I used this to check the resistance of the meter to verify that it is working. With the ohm scale on the meter set to 20k, the black lead is connected to ground and the red is brought into contact with the terminal on the sensor. It should indicate some reaking above .10K (depending on sensor spec). Generally, any resistance is an indication that the sensor is working, if the reading is zero or infinity then busted na yan.
Check mo rin yun recommendation ni sir ungas.

**yebo** · November 10th, 2004 05:17 PM

how do you know na hindi nga talaga dapat 3/4 ang reading? used a thermometer? are you sure yung assumptions mo ang correct, or yung temp reading ang correct?

**mantoy** · November 10th, 2004 06:28 PM

so if the temp reading is correct (3/4) , is there anything wrong with my cooling system? stable sya sa ganun reading whether the aircon is on or off.

**mantoy** · November 10th, 2004 06:35 PM

Originally posted by Field Master
The temp sensor is a variable-resistance sensor. To check the coolant-temperature sensor yourself, use a VOM -- or digital volt/ohm meter. I used this to check the resistance of the meter to verify that it is working. With the ohm scale on the meter set to 20k, the black lead is connected to ground and the red is brought into contact with the terminal on the sensor. It should indicate some reaking above .10K (depending on sensor spec). Generally, any resistance is an indication that the sensor is working, if the reading is zero or infinity then busted na yan.
Check mo rin yun recommendation ni sir ungas.

magkano naman yang VOM na yan? at san makakabili?

**Field Master** · November 10th, 2004 06:40 PM

VOM - Wag ka ng bumili, marami kang mahihiram nyan sa kapitbahay, yun mga friend mo na electronic enthusiasts meron nyan. Multitester kung tawagin yan ng iba. Yun sa akin nabili ko analog type 10 yrs ago 500 pesos yun.

**niky** · November 10th, 2004 07:57 PM

Sounds like an old problem of mine. It doesn't mean that if the sensor is by the same manufacturer that it will give the same voltage to the instrument cluster.