Hi - One of my current projects is to get a freezer working. I semi understand the basics. Repair seems to be by full replacement of faulty items ie thermostat, compressor, door!.
Included in this is the Starter relay. I understand what this does and have the following explanation from the internet:
The relay has a coil in it that is connected in series with the "run" winding in the compressor. When the power is applied, the compressor draws a high current as it is in a "stalled" state. This current is high enough to "pull" the relay in, which connects the "start" winding. This is connected through the capacitor which gives the start winding a "leading" state in electrical terms, which sets the motor rotating. As the motor speeds up, the current drops and is no longer sufficient to hold the relay up, and the motor continues to run without the "start" winding..
The neutral, or cold side of the motor is connected via a small thermal breaker which cuts the motor off if it doesn't start, until the breaker cools down, then it has another go at starting. This is the buzz and "Click" noise you sometimes hear if you turn your fridge off for a short period and then back on. The compreesor often wont start if the discharge pressure is too much greater than the suction.
Some compressors have a "run" capacitor as well which remains connected to give the motor a higher tourque, both for starting and running states.
All of this only takes a split second. This system has been replaced in many cases by electronic relays, but they don't have the ability to "read" the rotating state of the motor as well as the relay.
The guy who invented these relays should have received a medal. "
I believe the one I have is electronic so most of the above doesnt apply.
I have also looked up "how to test a relay" which brings up various ways of testing the electronmechanical type but says the "electronic" one can only be tested by an expert.
They are not expensive to replace - probably cheaper than asking an expert to test it but being of an inquisitive nature and willing to have a bash at mending most things decided to take it to bits. I expected to find an array of small electronic components but it just seems to have two contacts with a disk of some sort between them - almost zero resistance according to my
cheap vom. there is no internal connection to the common connector. I'd have thought +220vac to one side of a metallic disc and -220vac to the other would equal a big bang? I will have to investigate further where the common wire comes from- dont seem many wiring diagrams or schematics available on line. Might try the reference library.
I attach photos of the relay and perhaps someone can tell me if it looks like it should work or if it looks broken. The disk may have a pale coating on it but has rubbed off where the contacts touch it.
Included in this is the Starter relay. I understand what this does and have the following explanation from the internet:
The relay has a coil in it that is connected in series with the "run" winding in the compressor. When the power is applied, the compressor draws a high current as it is in a "stalled" state. This current is high enough to "pull" the relay in, which connects the "start" winding. This is connected through the capacitor which gives the start winding a "leading" state in electrical terms, which sets the motor rotating. As the motor speeds up, the current drops and is no longer sufficient to hold the relay up, and the motor continues to run without the "start" winding..
The neutral, or cold side of the motor is connected via a small thermal breaker which cuts the motor off if it doesn't start, until the breaker cools down, then it has another go at starting. This is the buzz and "Click" noise you sometimes hear if you turn your fridge off for a short period and then back on. The compreesor often wont start if the discharge pressure is too much greater than the suction.
Some compressors have a "run" capacitor as well which remains connected to give the motor a higher tourque, both for starting and running states.
All of this only takes a split second. This system has been replaced in many cases by electronic relays, but they don't have the ability to "read" the rotating state of the motor as well as the relay.
The guy who invented these relays should have received a medal. "
I believe the one I have is electronic so most of the above doesnt apply.
I have also looked up "how to test a relay" which brings up various ways of testing the electronmechanical type but says the "electronic" one can only be tested by an expert.
They are not expensive to replace - probably cheaper than asking an expert to test it but being of an inquisitive nature and willing to have a bash at mending most things decided to take it to bits. I expected to find an array of small electronic components but it just seems to have two contacts with a disk of some sort between them - almost zero resistance according to my
cheap vom. there is no internal connection to the common connector. I'd have thought +220vac to one side of a metallic disc and -220vac to the other would equal a big bang? I will have to investigate further where the common wire comes from- dont seem many wiring diagrams or schematics available on line. Might try the reference library.
I attach photos of the relay and perhaps someone can tell me if it looks like it should work or if it looks broken. The disk may have a pale coating on it but has rubbed off where the contacts touch it.
Attached Files
Usually, window aircons wouldn't restart till the pressure equalized, and the PTCs in fridges/freezers have no hope of starting anything till they cool off. Most newer window units with electronic controls have a 'compressor delay' to prevent short cycling.
) In modern compressors the thermal protection is almost always inside the compressor (at least the brands we have around here), if its busted you need a new compressor.
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