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Need advice on my issue: Blue (cold engine) light in the instrument panel stays on permanently. In addition yellow check engine light. ODB readout: Error Coolant Temperature Sensor hi. In Values: Coolant Temperature -42 C. (you can imagine how well the engine runs in 30C environment)
I have replaced the Coolant Sensor already twice. Works for 1 or 2 days, then same issue. Checked the voltage at the sensor and it is around 12V. Shouldn't it not be only 5 V as for all sensors? If the sensor is designed for 5 V then the 12 V would probably kill the resistor in short time. On the defective sensor there is unli Resistance = burnt through.
What would be the normal resistance between the 2 pins?
So maybe a Control box problem? Maybe 5 V regulator in the box burned through? I have replaced the box with another one from the scrapyard, however same issue. Still 12 V on the temperature sensor wire. (or its a common failure and the replacement box has the same issue)
Or potential shortcut in the wire harness?
Please, if you had a similar issue share your solution. Advice desired and appreciated.
What I replaced was not the Temperature/Cooland Sensor, it was the Fan Thermo Switch! That explains my weird measurements on the voltages.
In replacing the Thermo Switch, because it sits below the airbag, which needs to come out, I rattled and shaked on the harness. This movement of the harness provided intermittent contact to the rotting real Coolant Temperature Sensor. Therefor the intermittent success.
The Coolant temperature Sensor sits on the rear of the engine, not like the Coolant Thermo Switch below the airbox.
Defective rotten Coolant Temperature Sensor New Engine coolant temperature sensor (left side), versus new Thermo Switch (right side)
Tomorrow, during daylight they will go in the car ...then we see!
Looks like I was not measuring the Coolant Temp Sensor! I measured the thing below the airbox. Which is, as i have learned a thermo Switch! that explains the 12 V and the no connection between the pins when the switch is open. When its hot, it closes and probably switches on the cooling fan.
The real Coolant Sensor is located on the backside of the engine. While removing the airbox, i have of cause moved the wire harness a bit, which provided a little better connection on the slowly rotting sensor contacts. But only for short time ..i remember when the issue came up 1st, it was also weather dependent... a wet or humid sensor provided contact, a dry one not.
thats the rotten sensor from the rear side of the engine new Coolant Sensor on left side versus Thermo Switch on the right side.
Tomorrow during daylight they will be installed. With some luck, all is fine then.
issue is solved after swapping the real Coolant Sensor (rear side of engine). what I had swapped before and measured was the Thermo Switch (for the ventilator?) located below the airbox.
What I replaced was not the Temperature/Cooland Sensor, it was the Fan Thermo Switch! That explains my weird measurements on the voltages.
In replacing the Thermo Switch, because it sits below the airbag, which needs to come out, I rattled and shaked on the harness. This movement of the harness provided intermittent contact to the rotting real Coolant Temperature Sensor. Therefor the intermittent success.
The Coolant temperature Sensor sits on the rear of the engine, not like the Coolant Thermo Switch below the airbox.
Defective rotten Coolant Temperature Sensor New Engine coolant temperature sensor (left side), versus new Thermo Switch (right side)
Tomorrow, during daylight they will go in the car ...then we see!
03-05-2019, 10:31 AM
Well, found the solution:
