Problem with the coolant temperature gauge.

I have a 1998 ford ranger 3.0. I have replaced the coolant temp sensor sender. I have checked and the gauge is receiving power. I have used a jumper to test the gauge by grounding the sensor plug with the power on. When I do this the gauge on the panel reads full hot which indicates the gauge is good as well. I have no check engine light on. The heater woks very well so no air in the system. I can find no evidence of leaks. The truck does not over heat. The only problem is the coolant temperature gauge does not respond at all, it never moves while the truck is running. What could ca
Experienced mechanics share their insights in answering this question :
Hi there. The temperature gauge is not grounding out to the vehicle chassis. Try putting an additional wire on the housing of the temperature gauge and grounding it to the chassis. If this has no effect, then the gauge is not working and would need replaced. If you need further assistance with your temperature gauge, then seek out a professional, such as one from Your Mechanic, to help you.

How to Identify and Fix Common car Problems ?

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5. Fluctuating Temperature Gauge. The engine temperature gauge on your car`s dashboard gets its input from the coolant temperature sensor. A faulty sensor can cause it to fluctuate erratically as you drive.
If the temperature gauge still reads cold after the engine has warmed up, the gauge may simply be broken. Another reason the temperature gauge could read cold is if the thermostat in the vehicle stays open. With the thermostat stuck open, the engine can be overcooled, causing a low temperature reading.
COOLANT TEMPERATURE SENSOR FAULTY: SYMPTOMS

Frequent fault symptoms are: Higher idle speed. Increased fuel consumption. Poor starting behaviour.

The temperature gauge utilizes a sensor, located near or in the thermostat housing, to send an electrical signal through the vehicle`s internal computer corresponding to the specific coolant temperature, giving the gauge on your dashboard an accurate reading of the temperature.
Set your multimeter to Ohms X10K (or 10kΩ) mode and connect one of its probes to each of the two terminals in the temperature sensor connector. The gauge should register “OL” meaning that it has detected an open circuit between these two probes; if not, then the temperature sensor may be malfunctioning.
There may be several reasons for this:

Low coolant level delaying thermostat opening and closing (check coolant level in the radiator). Air pockets in the cooling system. A coolant leak. A partially clogged radiator.

The coolant temperature sensor (CTS) can be found somewhere near the engine thermostat, which allows it to function optimally. The tip of the CTS is probably located right next to the engine coolant. The sensor works by measuring the temperature that`s being given off by the thermostat and/or the coolant itself.
There will be a fused wire with voltage to the instrument cluster (your owners manual should indicate which fuse), but the temperature sensor is providing a variable “resistance to ground,” which the temperature gauge in the dash is reflecting.
When a thermistor is failing, it`ll display incorrect temperatures, or you`ll see impossible temperature fluctuations. For example, you may initially get a reading of 210 degrees only to see the temperature drop to 189 degrees and jump back up again.
There are two temperature sensors in some vehicles, one to send information from the engine system to the control unit and another from the control unit to the dashboard. The device follows the principle of dependence of potential difference in temperature.
The P0118 code refers to issues with the Engine Coolant Temperature (ECT) circuit and its accompanying sensor. The ECT is a thermistor, or an electrical resistor, whose resistance is significantly reduced by heating. The ECT is located in the coolant passage in your engine`s cylinder head.
If the needle in your car`s gauge doesn`t sit dead center, this is common. Every vehicle is different, and optimal temperature ranges may vary. The reading is affected by factors like the weather, using the heating, ventilation and air conditioning (HVAC) system or taxing the engine by towing heavy loads.
The fault with a coolant sensor can manifest in two ways- A coolant temperature sensor that always reads cold may cause the fuel management system to mix fuel with less oxygen and waste fuel. On the other hand, a sensor that always reads hot can cause problems such as stalling, hick-ups, and rough idling.
Reasons the Temperature Gauge Reads Cold

Another reason the temperature gauge is reading low is if the thermostat in the vehicle stays open. With the thermostat stuck open, the engine can be overcooled causing a low temperature reading. If this is the case, the thermostat may need to be replaced.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

No coolant in the reservoir. Seen low coolant message. I added 2 quarts of 50/50 coolant. Still getting the message. How much coolant doe it need?
ANSWER : Hi there. For the coolant light to go out, you would need to have the coolant between the low line and the full line for the light to go out. If the coolant is low and keeps on being low, then look for any signs of coolant leaks. You may have to use a coolant pressure tester to pressurize the reservoir to allow the leak to be found.

If you need further assistance with the coolant being low and the warning light being on, then seek out a professional, such as one from Your Mechanic, to help you.

Problem with the coolant temperature gauge.
ANSWER : Hi there. The temperature gauge is not grounding out to the vehicle chassis. Try putting an additional wire on the housing of the temperature gauge and grounding it to the chassis. If this has no effect, then the gauge is not working and would need replaced. If you need further assistance with your temperature gauge, then seek out a professional, such as one from Your Mechanic, to help you.

Car temperature keeps going up and coolant level drops.
ANSWER : Hi there. The milky engine oil is caused when the coolant from the cooling system gets into the engine oil. There are two ways that the coolant can mix with the oil on your vehicle. The first way is through the intake manifold as the gasket may crack causing the coolant to drain into the valley area making the coolant mix with the engine oil. However, the engine will not overheat quickly when this happens. The second way for the coolant to mix with the engine oil is through a burned head gasket. To verify that the head gasket is burned, get a block tester from your local parts store and set up the tool by putting the blue chemical in the tube and putting on the plunger on the end. Then remove the reservoir cap or radiator cap (take precautions of the coolant) and start the engine. Take the tool and place it over the inlet area to the reservoir or radiator. When steam starts to form in the area, use the plunger and suck in the steam into the tool. If there is any hydro carbons (raw unburnt fuel) in the cooling system, then the blue chemical will turn to a yellow or greenish color. If the color changes, the head gasket is burned and needs replaced. If the chemical does not change color, then the head gasket is good and there could be a leak on the intake gasket. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose your engine overheating issue.

Temperature gauge does not work – 1998 Mercury Grand Marquis
ANSWER : You will need to test the computer to scan for data of the temperature sensor to see if the computer is reading the correct temperature as tested externally on the coolant sensor. If the sensor is not accurate then replace the sender. If the sender is accurate then you will need to have the temperature gauge replaced.

Temperature gauge arrow climbs high, then returns to normal
ANSWER : There is a cooling fan clutch mounted on the radiator, and this device will move air across the radiator to cool the liquid coolant inside. The water pump is responsible for getting the coolant where it needs to go. With a new thermostat, and providing there are no air bubbles in the system, give another look at the fan function and the water pump. On extremely hot days, it is safe to see this kind of action as long as the temperature returns to normal. The cooling system is also affected by the high heat index and may need more time to get things going. If you would like to have this done, a certified professional from YourMechanic can come to your location to inspect the overheating problem.

Gas gauge isn’t working. Sometimes the speedometer and the temperature gauge doesn’t work. Limited lights around gauges and radio.
ANSWER : Hi there. The dashboard lights are burned out in the dash and the dimmer switch could be worn causing the lights to be weak. The gauges that seldom fail to work is most likely a loose wire in the dash panel. The fuel gauge that is not going to E when shutting off the car has a damaged rheostat within the sending unit. The sending unit is in the fuel tank attached to the fuel pump. If you need further assistance with your gauges not working, then seek out a professional, such as one from Your Mechanic, to help you.

Engine coolant temperature problem
ANSWER : You may have a persistent overheating issue due to a clogged radiator, blown head gasket, worn out water pump, etc. This should be checked out by a professional mechanic immediately to avoid being stranded or causing further damage. A professional, like one from YourMechanic, can determine the source of the problem and make needed repairs.

This is Luis from Mesa, AZ. I have a 2000 Maxima. Temp gauge rises when coolant level is normal, but when level drops, gauge reads
ANSWER : Hello Luis, thank you for writing in. If the vehicle is leaking coolant, and you are seeing white smoke or steam from the exhaust, then your engine is consuming the coolant. This happens when your head gasket allows coolant to flow into the combustion chambers. It is also why you are likely only loosing coolant when you drive. At this point, do not worry about the other symptoms. Most of them may rule themselves out when the head gasket is repaired. If there has been any further damaged to the cooling system, we can sort them out after the leak is taken care of. Keep in mind the coolant overflow tank needs room in it in case the cooling system heats up and the coolant expands, it needs a place to drain into so you do not loose that coolant. For more help replacing the head gasket, contact our service department to schedule an appointment.