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You need to first understand the way the resistor is "put together". There are various different types, and you didn't specify. For example, there are simple bulk resistors where everything in the electrical path lies on a straight line. In a wirewound resistor, the resistor element is wound in a spiral around a cylinder. Or you could be talking about a resistor in an Integrated Circuit (IC) or on a thick-film hybrid circuit. You could be talking about a small "chip" resistor that goes onto a PCB. You need to be more specific to get a more specific answer.
The first thing you should determine is if the resistor is actually open, or if you simply have a bad connection to the resistor. Is it soldered to something? If so, use an ohmmeter equipped with pointed probes to check for connection on either side of both of the resistor's solder joints, if possible. If this is not possible (such as in the case of a surface mount "chip" resistor), you have to consider the solder joint as part of the resistor in the investigation.
In fact, you should keep in mind that failure of a solder joint is MUCH more likely than simple failure of a resistor, unless the resistor has had too much current passed through it. Resistors tend to be mechanically more robust and reliable than solder joints.
If the resistor was electrically overstressed (too much current, causing too much power dissipation/heat) the point of failure should be fairly obvious. There will be black, carbonized material at the failure point. You may need an optical microscope to see it, and it could be internal. There may be other external signs, such as bulging or discoloration that are not as obvious.
If the resistor is not truly open but merely very high resistance, it may be possible to thermally image the fault location. Care must be taken to not pass through too much current and make the fault worse (unless you only care about the fault's location and not its cause).
A high resolution x-ray can be used to image and find electrical opens in some types of resistors. It may also be possible to use more advanced tools such as Acoustic Tomagraphy, but that is rarely justified for using on a resistor that has become open. There are simpler, cheaper techniques that will give good results. The big advantages to x-ray and Acoustic Tomagraphy are that they can be done non-destructively.
If it is a true electrical open, you generally expose the conductive element by stripping off the exterior chemically, or by cross-sectioning the device. Opens can then usually be spotted with simple optical microscopy. If the defect is too small, a Scanning Electron Microscope (SEM) can be used to image it. If one lead of the resistor is grounded, the un-grounded part of the resistor will quickly accumulate a charge and start to "glow" in the SEM, exposing the site of the open.
Remember, if you couldn't verify that the solder connections to the resistor were OK, you have to consider them as possible points of failure in the analysis.
What else can I help you with?
What is neutral grounding resistor panel?
A neutral grounding resistor panel is used to resist fault current to the ground. It is used for alternator protection protection purposes. When a fault occurs in the alternator, the panel helps force the current to the ground.
How designing stabilizing resistor in restricted earth fault relay?
To determine the value of Stabilizing resistor Rs = Vs/Is = If(Rct +2Rl)/Is Where, Rs = resistance value of the stabilizing resistor Vs = voltage at which the relay will operate Is = current flowing through the stabilizing resitor and the relay If = maximum secondary fault current magnitude Rct = internal resistance of the current transformer Rl = resistance of attached wire leads
When a needle of an analog ohmmeter indicates infinity the resistor being measured is?
Open
Why remove resister from circuit to measure resistance?
a meter uses its own supply to measure resistance. you dont have to remove the resistor from the circuit but you must isolate it from the circuit supply to get an accurate reading.
Most common failure in a resistor?
This depends on the type of resistor. Carbon composition and metal film resistors typically will burn open, carbon film types can short.
Why neatural ground resistor using in 33kv transformer?
The function of a neutral earth resistor is to limit any fault current resulting from fault between a line conductor and earth.
What neutral ground resistor?
A neutral ground resistor is a type of grounding system used in electrical systems to limit the amount of fault current that can flow through the system during a ground fault. It helps protect equipment and personnel from electrical hazards by reducing the voltage levels that could result from ground faults. The resistor is typically installed between the neutral and ground connection points of the system.
Does an open resistor measure 0 ohms?
No, an open resistor has a value of infinity. An open resistor typically will measure over 900 Megohms. A zero ohm resistor is exactly that, and will measure zero ohms. They are typically surface-mount devices.
How does a Neutral grounding resistor work?
A neutral grounding resistor limits the fault current flowing through the neutral point of a power system during a ground fault. It helps to reduce the risk of damage to equipment and prevents excessive voltage levels on the system. By limiting the fault current, the resistor provides a safe path for fault currents to flow and helps in isolating the faulted section of the system.
What are the common defects of a variable resistor?
Normally if a resistor fails they will either increase in value or open up at all (open circuit).
What is neutral grounding resistor panel?
A neutral grounding resistor panel is used to resist fault current to the ground. It is used for alternator protection protection purposes. When a fault occurs in the alternator, the panel helps force the current to the ground.
Why does my blower fan run at all speeds except max Like the opposite of the normal resistor failure?
wiring fault. at max speed the resistor is bypassed
What is open on fault?
There are isolation devices (Circuit breakers) meant to cut off or OPEN automatically when a fault occurs. The breaker has "opened" on fault.
How can you check if 50 mega ohms resistor is open?
use a merger tester, if there are no indication to certain number of ohmic (50 M), that is mean resistor is open.
How to know if the resistor is open and shorted?
I assume that the person asking the question meant "open OR shorted" as these are opposite terms. Most resistors will open when they are damaged. It is very rare to find one that is shorted. To determine if the resistor is open or shorted simply use a multimeter set to measure ohms. Place the leads across the resistor and it should read the resistance value of the resistor. If it measures max range of the meter (some digitals will display "OL") then the resistor is open. If it measures 0 or very close then it is shorted, which as mentioned above, is unlikely.
How designing stabilizing resistor in restricted earth fault relay?
To determine the value of Stabilizing resistor Rs = Vs/Is = If(Rct +2Rl)/Is Where, Rs = resistance value of the stabilizing resistor Vs = voltage at which the relay will operate Is = current flowing through the stabilizing resitor and the relay If = maximum secondary fault current magnitude Rct = internal resistance of the current transformer Rl = resistance of attached wire leads
No power at the blower motor resistor?
Since you're checking the resistor, I would assume you checked the fuse/relay for the blower motor. If not check that. If you have then there would be an open wire between the relay and the resistor.
