Hi,

I was troubleshooting my sister's donated old Viking window AC which
she said wouldn't cool a couple summers ago. Found the defrost
interruptor contact was open with traces of smoke on the case. I
jumpered it and noticed the compressor seemed to be binding at every
other start attempt. When it wouldn't start it tripped my powerbar's
breaker so that explains why the defrost contact burned. The 25uF
starting cap seems okay. It measures alright and low leakage. After a
few careful starts the compressor now runs every time.

I've heard of AC compressors locking up if not used for a very long
time. I'm guessing the oil drains out of the bearings. It seems it
will run fine from here on and it really cools fast. I'll just have to
be careful about starting it next summer and use the powerbar with
breaker.

I have a couple of question's about the defrost contact. Is it simply
a fail-safe device or is it needed to turn off the compressor as part
of normal operation? Are these pretty generic?

This one clips onto the cold end return and made by Klixon (Made in
USA) # 20425F21-439-780 F56-3.0 6CV Not too sure about the F56-3.0 as
it was smudged. It was held in place by a thick tape ressembling
mastic, some kind of thermal insulation?

TIA

A*s*i*m*o*v

.... [] - Please write your complaint legibly in that box.

"Asimov" writes:

Hi,

I was troubleshooting my sister's donated old Viking window AC which
she said wouldn't cool a couple summers ago. Found the defrost
interruptor contact was open with traces of smoke on the case. I
jumpered it and noticed the compressor seemed to be binding at every
other start attempt. When it wouldn't start it tripped my powerbar's
breaker so that explains why the defrost contact burned. The 25uF
starting cap seems okay. It measures alright and low leakage. After a
few careful starts the compressor now runs every time.

I've heard of AC compressors locking up if not used for a very long
time. I'm guessing the oil drains out of the bearings. It seems it
will run fine from here on and it really cools fast. I'll just have to
be careful about starting it next summer and use the powerbar with
breaker.

I have a couple of question's about the defrost contact. Is it simply
a fail-safe device or is it needed to turn off the compressor as part
of normal operation? Are these pretty generic?

This one clips onto the cold end return and made by Klixon (Made in
USA) # 20425F21-439-780 F56-3.0 6CV Not too sure about the F56-3.0 as
it was smudged. It was held in place by a thick tape ressembling
mastic, some kind of thermal insulation?

None of my ACs have such a sensor so I doubt it's needed to prevent
damage to anything.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the Feedback Form in the FAQs.

"Asimov" wrote in message
...
Hi,

I was troubleshooting my sister's donated old Viking window AC which
....
I've heard of AC compressors locking up if not used for a very long
time. I'm guessing the oil drains out of the bearings. It seems it

+ Unusual for a sealed unit. It does need to sit in the normal working
position for a while before it is fired up.

....
I have a couple of question's about the defrost contact. Is it simply
a fail-safe device or is it needed to turn off the compressor as part
of normal operation? Are these pretty generic?

+ You don't want to freeze up the evaporator, so it's needed IMO.

This one clips onto the cold end return and made by Klixon (Made in
USA) # 20425F21-439-780 F56-3.0 6CV Not too sure about the F56-3.0 as
it was smudged. It was held in place by a thick tape ressembling
mastic, some kind of thermal insulation?

+ Possible tape that has dissolved over time? Double sided foam tape?

N

Sam Goldwasser wrote in message ...
"Asimov" writes:

Hi,

I was troubleshooting my sister's donated old Viking window AC which
she said wouldn't cool a couple summers ago. Found the defrost
interruptor contact was open with traces of smoke on the case. I
jumpered it and noticed the compressor seemed to be binding at every
other start attempt. When it wouldn't start it tripped my powerbar's
breaker so that explains why the defrost contact burned. The 25uF
starting cap seems okay. It measures alright and low leakage. After a
few careful starts the compressor now runs every time.

I've heard of AC compressors locking up if not used for a very long
time. I'm guessing the oil drains out of the bearings. It seems it
will run fine from here on and it really cools fast. I'll just have to
be careful about starting it next summer and use the powerbar with
breaker.

I have a couple of question's about the defrost contact. Is it simply
a fail-safe device or is it needed to turn off the compressor as part
of normal operation? Are these pretty generic?

This one clips onto the cold end return and made by Klixon (Made in
USA) # 20425F21-439-780 F56-3.0 6CV Not too sure about the F56-3.0 as
it was smudged. It was held in place by a thick tape ressembling
mastic, some kind of thermal insulation?

None of my ACs have such a sensor so I doubt it's needed to prevent
damage to anything.

Maybe it is a sensor to shut the airconditioner down in case the
temperature gets too cold and there is danger of too much frost/ice on
the cooling coils, or maybe a shutoff if the compressor temperature
gets too high. You don't say where this sensor is located, as far as
I can tell.

H. R. (Bob) Hofmann

"H. R. Bob Hofmann" wrote in message
om...

| Maybe it is a sensor to shut the airconditioner down in case the
| temperature gets too cold and there is danger of too much frost/ice on
| the cooling coils, or maybe a shutoff if the compressor temperature
| gets too high. You don't say where this sensor is located, as far as
| I can tell.

From "clips onto the cold end return" I assume it's on the input to the
compressor.

N

"NSM" writes:

"H. R. Bob Hofmann" wrote in message
om...

| Maybe it is a sensor to shut the airconditioner down in case the
| temperature gets too cold and there is danger of too much frost/ice on
| the cooling coils, or maybe a shutoff if the compressor temperature
| gets too high. You don't say where this sensor is located, as far as
| I can tell.

From "clips onto the cold end return" I assume it's on the input to the
compressor.

I expect it is a sensor to shut down the compressor if ice forms since
that's a runaway situation - once the ice is present, more ice will
form until the evaporator is a solid block of ice and no cooling of
the room takes place.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header is ignored.
To contact me, please use the Feedback Form in the FAQs.

"Sam Goldwasser" bravely wrote to "All" (19 Nov 04 08:08:25)
--- on the heady topic of " AC defrost"

SG From: Sam Goldwasser

SG "NSM" writes:

"H. R. Bob Hofmann" wrote in message
om...

| Maybe it is a sensor to shut the airconditioner down in case the
| temperature gets too cold and there is danger of too much frost/ice on
| the cooling coils, or maybe a shutoff if the compressor temperature
| gets too high. You don't say where this sensor is located, as far as
| I can tell.

From "clips onto the cold end return" I assume it's on the input to the
compressor.

SG I expect it is a sensor to shut down the compressor if ice forms since
SG that's a runaway situation - once the ice is present, more ice will
SG form until the evaporator is a solid block of ice and no cooling of
SG the room takes place.


Yes, I think it is there to keep ice from building up on the room
radiator fins. This is Canada after all, and though the days are very
warm in the fall, the nights get cold. I wrote the sensor clips onto
the radiator return line but I was mistaken, it is the pipe that
brings the cold coolant into the room radiator. Sorry for the mixup.

What I still don't know is if the defrost interrupter contact is used
in normal operation or if it is simply a fail-safe device in case of
an abnormal event like the main thermostat getting stuck? It is too
cold to test right now and I don't know if I should go looking for the
part if it isn't really needed.

A*s*i*m*o*v

.... If all else fails, hurl it across the room a few times!

"H. R. Bob Hofmann" bravely wrote to "All" (18 Nov 04 20:57:38)
--- on the heady topic of " AC defrost"

HRBH From: (H. R. Bob Hofmann)

HRBH Sam Goldwasser wrote in message
HRBH ... "Asimov"
HRBH writes:
Hi,

I was troubleshooting my sister's donated old Viking window AC which
she said wouldn't cool a couple summers ago. Found the defrost
interruptor contact was open with traces of smoke on the case. I
jumpered it and noticed the compressor seemed to be binding at every
other start attempt. When it wouldn't start it tripped my powerbar's
breaker so that explains why the defrost contact burned. The 25uF
starting cap seems okay. It measures alright and low leakage. After a
few careful starts the compressor now runs every time.

I've heard of AC compressors locking up if not used for a very long
time. I'm guessing the oil drains out of the bearings. It seems it
will run fine from here on and it really cools fast. I'll just have to
be careful about starting it next summer and use the powerbar with
breaker.

I have a couple of question's about the defrost contact. Is it simply
a fail-safe device or is it needed to turn off the compressor as part
of normal operation? Are these pretty generic?

This one clips onto the cold end return and made by Klixon (Made in
USA) # 20425F21-439-780 F56-3.0 6CV Not too sure about the F56-3.0 as
it was smudged. It was held in place by a thick tape ressembling
mastic, some kind of thermal insulation?

None of my ACs have such a sensor so I doubt it's needed to prevent
damage to anything.

HRBH Maybe it is a sensor to shut the airconditioner down in case the
HRBH temperature gets too cold and there is danger of too much frost/ice on
HRBH the cooling coils, or maybe a shutoff if the compressor temperature
HRBH gets too high. You don't say where this sensor is located, as far as
HRBH I can tell.


It is not the compressor overheat interruptor contact. There already
is one attached to the compressor body right inside its wiring box.
The defrost interrupter contact clips onto the the pipe bringing the
cold coolant into the room radiator.

A*s*i*m*o*v

.... A fail-safe circuit will destroy others.

"Asimov" wrote in message
...

Yes, I think it is there to keep ice from building up on the room
radiator fins. This is Canada after all, and though the days are very
warm in the fall, the nights get cold. I wrote the sensor clips onto
the radiator return line but I was mistaken, it is the pipe that
brings the cold coolant into the room radiator. Sorry for the mixup.

What I still don't know is if the defrost interrupter contact is used
in normal operation or if it is simply a fail-safe device in case of
an abnormal event like the main thermostat getting stuck? It is too
cold to test right now and I don't know if I should go looking for the
part if it isn't really needed.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

It should cut off the compressor but not the fan. That way the fan will help
clear the evaporator ("radiator") and clear the water that condenses from
it. It's OK for it to operate in normal use - high humidity and cool
temperatures for example.

N

"NSM" bravely wrote to "All" (20 Nov 04 07:37:57)
--- on the heady topic of " AC defrost"

NS From: "NSM"

NS "Asimov" wrote in
NS message ...
NS What I still don't know is if the defrost interrupter contact is used
NS in normal operation or if it is simply a fail-safe device in case of

NS It should cut off the compressor but not the fan. That way the fan
NS will help clear the evaporator ("radiator") and clear the water that
NS condenses from it. It's OK for it to operate in normal use - high
NS humidity and cool temperatures for example.

Indeed, it cuts off the compressor only. It makes sense about it
operating during high humid and cool periods. Thanks.

A*s*i*m*o*v

.... I worked hard to attach the electrodes to it.