A/C Questions

I have a '91 Explorer with a malfunctioning (R12) A/C.

Earlier this season the A/C was working, but not real cold. When the
temps hit on the 90's, I added my last can of freon. After adding
the freon, I found that the compressor clutch was not cycling. The
air is very cold, but I am concerned that the system might be
overfilled.

Questions:
How do I test to see if the system is overcharged?
How can I check to see if the cycling problem is due to a bad cycle
switch?
I am assuming that running the compressor at a 100% duty cycle will
damage the system. Is this correct?

Thanks
John Normile

"John Normile" > wrote in message
. ..
> I have a '91 Explorer with a malfunctioning (R12) A/C.
>
> Earlier this season the A/C was working, but not real cold. When the
> temps hit on the 90's, I added my last can of freon. After adding
> the freon, I found that the compressor clutch was not cycling. The
> air is very cold, but I am concerned that the system might be
> overfilled.
>
> Questions:
> How do I test to see if the system is overcharged?
> How can I check to see if the cycling problem is due to a bad cycle
> switch?
> I am assuming that running the compressor at a 100% duty cycle will
> damage the system. Is this correct?
>
> Thanks
> John Normile

I have a hard time getting mine (when fully charged) to cycle off on a hot
day. Did you try it early in the morning or late at night?

To test my system on my newer Explorer with the other refrigerant (whatever
it's called) I use a pressure gauge that came with an A/C recharge kit.
Older cars had a "sight glass" and you looked for bubbles when you turned
off the A/C. You might have a hard time finding a kit for an R12 system at
an auto parts store. eBay perhaps?

The A/C on some of the newer Explorers comes on with the defrost cycle and
it's my understanding that on some cars once you turn on defrost the
compressor will continue to be active until you turn off the engine so my
guess would be that it's probably not real bad that it stays on.

On Sat, 02 Aug 2008 19:42:26 -0700, Ashton Crusher >
wrote:

>On Tue, 29 Jul 2008 22:26:00 GMT, (John Normile)
>wrote:
>
>>I have a '91 Explorer with a malfunctioning (R12) A/C.
>>
>>Earlier this season the A/C was working, but not real cold. When the
>>temps hit on the 90's, I added my last can of freon. After adding
>>the freon, I found that the compressor clutch was not cycling. The
>>air is very cold, but I am concerned that the system might be
>>overfilled.
>>
>>Questions:
>>How do I test to see if the system is overcharged?
>>How can I check to see if the cycling problem is due to a bad cycle
>>switch?
>>I am assuming that running the compressor at a 100% duty cycle will
>>damage the system. Is this correct?
>>
>>Thanks
>>John Normile
>
>
>My experience has been that if you are adding freon in hot weather it
>is darn near impossible to overfill a system. The only sure way to
>check overcharge is with gauges. I believe there is a high pressure
>blowout valve sticking out the back side of the compressor. If it's
>truly overfilled and runs way too much pressure that valve will blow
>out. The AC in these is marginal in hot weather so it would not
>surprise me that it needed to run constantly at this time of year.

Ashton, thanks for the reply.
I have a set of gauges but the factory manual I have doesn't have any
readings for them. So I wouldn't know how to interpret the readings.
Any idea what they should read?

The A/C in this Explorer has always been real strong. And it was
not uncommon that I could not run it full blast, even in the hottest
weather. Now it's in the mid 90's, and the temp at the vents is well
bellow 50.

Contrary to what you have been told, it is not only possible to overcharge a
system no matter what the temp (excluding extreme cold) but it is possible
to introduce enough refrigerant as to destroy the compressor if you are not
familiar with the systems and their properties...

High side pressures are dependant upon ambient temperature and humidity....
rather than reinvent the wheel, I stumbled arouind in Google for a very few
minutes and came up with this
http://www.johnnysradiatorshop.com/files/32332467.doc - I scanned through
it quickly and think it should answer all of your questions and do so with
reasonably good answers... FWIW, low side pressures are "controlled' (not
the best word for what happens) by the low pressure cutout switch.

The proper way to charge any AC system is by weight of the refrigerant...
while you can sometimes get away with a SOTP gauge reference method, this
may not be in anyones best interests... I haven't had to work with R12
systems for several years (they are nearly outlawed in Cananda... if you
have one and it works - good for ya... if you have one and it don't - this
gets gnarly... DIYers are allowed to do things that would have my licence
revoked.

HTH

Top posted - as usual.

Somehow the old fool managed to hit "rely to sender" as opposed to "reply to
group"...

Does this look familiar?

>My experience has been that if you are adding freon in hot weather it
>is darn near impossible to overfill a system.

Even on the oldest systems, there is a "best way" to do things.... This
"best way" is to charge by weight. Are there guidelines regarding system
performance - yes.... But your best results will be by charging by
weight.... (Let's not belabour any environmental considerations). We can use
the sight glass - the "electronic" sight glass, pressures - temperatures -
or a combination of any of these.... None are truly accurate.

Guages are for performance testing systems and are not a real good measure
of how much of what is in the system.... Look at it this way - there are
those of us trying to treat "your" planet with the utmost respect..... the
least you couild do is return the favour....

> wrote in message
news:fz7nk.4907$%b7.2710@edtnps82...
> Does this look familiar?
>
> >My experience has been that if you are adding freon in hot weather it
> >is darn near impossible to overfill a system.
>
> Even on the oldest systems, there is a "best way" to do things.... This
> "best way" is to charge by weight. Are there guidelines regarding system
> performance - yes.... But your best results will be by charging by
> weight.... (Let's not belabour any environmental considerations). We can
use
> the sight glass - the "electronic" sight glass, pressures - temperatures -
> or a combination of any of these.... None are truly accurate.
>
> Guages are for performance testing systems and are not a real good measure
> of how much of what is in the system.... Look at it this way - there are
> those of us trying to treat "your" planet with the utmost respect..... the
> least you couild do is return the favour....
>
>

OK, for example, my '78 F350 says on the AC compressor how many pounds of
R12 it should have in there. So, in order to do it by weight, does all of
the R12 need to be evacuated and then replaced? This does not seem to be
within the scope of most DIYers. Or is it?
>

Yes, the system needs to be evacuated. No... it isn't within the scope of
most DIYers.... And this should be telling you something... I can't speak
for the US - in Canada, if you have an R12 system that needs servicing, it
will not be an R-12 system when you are done. As an automotive shop, we
can't purchase R-12....

Open heart surgery isn't within the scope of most DIYers.... DNA testing
isn't within the scope of DIYers.... closer to home - accurate (or properly
performed) voltage drop testing... and we can add any number of other
operations....

If we are not properly equipped to do something... why would we attempt? If
I don't have the proper equipment in my shop to perform a test or repair on
your car, will you pay me for the attempt?

Look at it this way... how can you ice skate if you don't have a pair of ice
skates?


"Ulysses" /> wrote in message
news
>
> > wrote in message
> news:fz7nk.4907$%b7.2710@edtnps82...
>> Does this look familiar?
>>
>> >My experience has been that if you are adding freon in hot weather it
>> >is darn near impossible to overfill a system.
>>
>> Even on the oldest systems, there is a "best way" to do things.... This
>> "best way" is to charge by weight. Are there guidelines regarding system
>> performance - yes.... But your best results will be by charging by
>> weight.... (Let's not belabour any environmental considerations). We can
> use
>> the sight glass - the "electronic" sight glass, pressures -
>> temperatures -
>> or a combination of any of these.... None are truly accurate.
>>
>> Guages are for performance testing systems and are not a real good
>> measure
>> of how much of what is in the system.... Look at it this way - there are
>> those of us trying to treat "your" planet with the utmost respect.....
>> the
>> least you couild do is return the favour....
>>
>>
>
> OK, for example, my '78 F350 says on the AC compressor how many pounds of
> R12 it should have in there. So, in order to do it by weight, does all of
> the R12 need to be evacuated and then replaced? This does not seem to be
> within the scope of most DIYers. Or is it?
>>
>
>