Content of the material
- Appliance Repair Safety Protocols
- Bad Dryer Thermistor or Thermostat
- Using Self -Diagnostics to Test for the Thermistors?
- Two types of thermistor
- NTC Thermistor
- PTC Thermistor
- How to test an NTC thermistor
- REFERENCE LINKS
- Next Step
- Schedule Heating AC Inspection
- How to Choose a Replacement Thermistor
- Symptoms of a faulty thermistor
- Testing a Thermistor
- How to Tell Before a Thermistor Goes Faulty
- 2. Dryer Making Noise
- Damaged Drum Rollers or Bearings
- Worn Dryer Belt
Appliance Repair Safety Protocols
- Start every refrigerator repair by unplugging your appliance and turning off its water supply valves.
- Wear work gloves and safety glasses to prevent unnecessary injuries while working on your refrigerator.
- If you’re having difficulty repairing your refrigerator, please call a professional appliance repair technician to take over the job.
Bad Dryer Thermistor or Thermostat
Symptoms of a bad dryer thermistor include air in the dryer that won’t heat up. If the dryer does heat up, a bad dryer thermostat can result in loss of temperature control. If you have a faulty dryer thermostat, the dryer may keep the heat on for too long, causing the dryer to get too hot. If the cycling thermostat is defective, the dryer will not heat up.
According to PartSelect, if the cycling thermostat in the dryer becomes defective, it will not be able to accurately sense the airflow temperature. It can cause the heater or gas burner to stay on too long. Testing the thermostat is not easy to do, so you should first inspect the other more commonly faulty parts. If you do test your dryer’s cycling thermostat, use a multimeter, and the test should give you a reading of either zero or infinity. If your test produces any other reading, the cycling thermostat needs to be replaced.
The high-limit thermostat can also be tested. This thermostat is only activated when heat rises and trips the thermostat. Sometimes, the contacts may fuse together and no longer be active. Test the high-limit thermostat in a similar way as the cycling thermostat: Touch the terminals with the probes and replace the high-limit thermostat if you get a result other than zero.
Using Self -Diagnostics to Test for the Thermistors?
Not if you value your time.
You certainly can run the self-diagnostics but this test can only detect a closed or open circuit and thermistors normally do not fail this way. Instead, sintered non-oxides in thermistors lose its potency and lose their ability to provide correct resistance.
Two types of thermistor
- NTC (Negative temperature co-efficient)
- PTC (Positive temperature co-efficient)
Shows a decrease of electrical resistance when the system water increases in temperature and shows an increase of electrical resistance when the system water decreases in temperature.
These decrease the resistance proportionally with an increase in temperature. For example 25 degrees C to start at 12,000 Ohms, to 55 degrees C at 4,000 Ohms. As the temperature goes up, resistance comes down.
Typical starting resistances are in the range of 12-15,000 Ohms (12-15k Ohms), down as low as 900 Ohms when boiling.
Shows an increase of electrical resistance when the system water increases in temperature and shows a decrease of electrical resistance when the system water decreases in temperature.
This is the opposite of an NTC. As the temperature increases proportionally with temperature rise. They are identical to look at as an NTC, they just behave differently.
From a 10 degree start at 800 Ohms, up to 90 degrees at 1600 Ohms. They are less common than NTC thermistors.
How to test an NTC thermistor
Unless you can see a wire has come loose you are unlikely to see anything physically wrong. Diagnosis is done by measuring the resistance with a continuity (or multi) meter. I can’t give readings for all thermistors because they vary, especially in different types of appliance, but you should be able to get a reading across both terminals. If it’s completely open circuit it’s likely to be faulty.
- Thermistors (external link, Wikipedia)
- Thermistors and NTC Thermistors (external link, electronics-tutorials.ws)
- Temperature Sensors (external link, electronics-tutorials.ws)
- Troubleshooting Thermistor Problems in refrigerators (external link, YouTube-Sears Parts Direct)
- Sintered Metal Oxide for Thermistor (external link, US Patents-Google)
Schedule Heating AC Inspection
The most popular service booked by readers of this article is Heating AC Inspection. Once the problem has been diagnosed, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. YourMechanic’s technicians bring the dealership to you by performing this job at your home or office 7-days a week between 7AM-9PM. We currently cover over 2,000 cities and have 100k+ 5-star reviews… LEARN MORESEE PRICING & SCHEDULING
How to Choose a Replacement Thermistor
There are two main types of thermistors. The first is negative temperature coefficient (NTC) thermistors. NTC thermistors decrease resistance when temperatures increase. The second is positive temperature coefficient (PTC) thermistors, which increase their resistance when the temperature increases. If you need a replacement thermistor, ask yourself the following questions:
- What’s the base resistance of the thermistor you’re replacing?
- What base resistance does your application need?
- How do resistance and temperature relate to this application? Should resistance decrease or increase as the temperature rises?
- What’s the ideal thermistor size and style for your application?
Symptoms of a faulty thermistor
If a thermistor goes faulty it could either fail to give any temperature readings or give incorrect ones. If it no longer registers any temperature change the appliance should overheat if it’s used in conjunction with heating elements, or if used in refrigeration it could cause temperatures to get too low. In most cases however, appliances using these devices are sophisticated enough to recognise the sensor isn’t working and produce some error code.
Testing a Thermistor
To check the accuracy of your thermistor, you will need:
- A thermistor
- A heating device of any kind, such as a blow dryer or space heater
- A multimeter with an ohmmeter
Once you have your materials, you can begin evaluating your thermistor in a few quick steps.
- Step 1: Make note of the current reading on your thermistor.
- Step 2: Change the resistance value to its rated resistance value. If you cannot set to the rated value, this is an immediate sign that you are in need of a new thermistor.
- Step 3: Apply heat to the thermistor and watch for changes. Thermistors should be able to adjust in seconds, so ff you do not see immediate resistance fluctuation, your product is faulty.
How to Tell Before a Thermistor Goes Faulty
Want to get ahead of thermistor failure? Generally speaking, symptoms of a faulty thermistor present themselves before the thermistor goes completely bad. Usually, they are the same or similar issues as faulty thermistor symptoms. So, what are symptoms of a faulty thermistor before it goes bad? They include:
- Temperature fluctuations
- Incorrect temperature readings
- Blower motor broken or cold air for only a short time (in car A/C systems with thermistors)
While these may indicate a thermistor that’s not quite right, you can confirm for sure by testing your thermistor! That’s the most surefire way of knowing if a thermistor is faulty.
2. Dryer Making Noise
Another common problem with Samsung dryers is a rattling, squeaking, or grinding noise. The noise is usually caused by damaged rollers or bearings, a worn-out dryer belt, or a defective idler pulley.
Damaged Drum Rollers or Bearings
If the drum rollers or bearings are damaged, the dryer will make loud, unusual noises, usually a grinding or squeaking noise. Some dryer models have two rollers at the back of the dryer, while others have two at the front and two at the back. The rollers also have bearings in them, which can wear on the axles. When you examine the rollers, make sure that they spin freely. If the rollers have completely worn out, they are likely to have also damaged the axles. If a roller, axle, or bearing is damaged, it will need to be replaced.
Worn Dryer Belt
The dryer belt is part of the pulley system that rotates the dryer drum. A loud thumping noise indicates that the dryer belt is worn or broken and needs to be replaced. A drum that cannot easily be rotated also indicates a faulty dryer belt. To check the dryer belt, unscrew the relevant access panel. If the belt is broken or loose, replace the belt.