A/C problem
 

I have a 97 Jeep Cherokee. Now that it's the summer I want to use my air conditioning. However, when I turn on the A/C, no cold air is put out and the compressor clutch cycles on and off, as if it were in defrost mode. I am sure it is set on max a/c with the fan on high, and still the clutch cycles on and off. I also checked the pressure of the Freon and that is where it's supposed to be. I was thinking it might be a relay of somesort that controls the clutch, maybe it is stuck it the defrost position? Any help would be greatly appreciated.

Your low pressure switch is disconnecting the clutch because you
have less than twenty pounds in the suction side while pumping, it
should be between 34 and 38.
God Bless America, ßill O|||||||O
http://www.billhughes.com/

MPClark wrote:
>
> I have a 97 Jeep Cherokee. Now that it's the summer I want to use my air
> conditioning. However, when I turn on the A/C, no cold air is put out
> and the compressor clutch cycles on and off, as if it were in defrost
> mode. I am sure it is set on max a/c with the fan on high, and still
> the clutch cycles on and off. I also checked the pressure of the Freon
> and that is where it's supposed to be. I was thinking it might be a
> relay of somesort that controls the clutch, maybe it is stuck it the
> defrost position? Any help would be greatly appreciated.
>
> --
> MPClark

The problem is insufficient freon in the system. Fixing it is a two step
process. (1) Find the leak. (2) Evacuate the system and fill it with the
exact amount of refrigerant required.

If you were a redneck shade-tree mechanic, you might get one of those
twelve-ounce cans of freon, that comes with its own recharge hose, and fill
the system until you thought it was working properly. This might work, but
for long-term satisfaction you have to find and fix that leak.

Earle

"L.W. (ßill) Hughes III" > wrote in message
...
> Your low pressure switch is disconnecting the clutch because you
> have less than twenty pounds in the suction side while pumping, it
> should be between 34 and 38.
> God Bless America, ßill O|||||||O
> http://www.billhughes.com/
>
> MPClark wrote:
> >
> > I have a 97 Jeep Cherokee. Now that it's the summer I want to use my air
> > conditioning. However, when I turn on the A/C, no cold air is put out
> > and the compressor clutch cycles on and off, as if it were in defrost
> > mode. I am sure it is set on max a/c with the fan on high, and still
> > the clutch cycles on and off. I also checked the pressure of the Freon
> > and that is where it's supposed to be. I was thinking it might be a
> > relay of somesort that controls the clutch, maybe it is stuck it the
> > defrost position? Any help would be greatly appreciated.
> >
> > --
> > MPClark

it's against the law to knowly charge a leaking a/c system and leave the charge
in if the leak is not repaired
don't try to use a can with sealer it react to o2 to seal the leak so any o2 in
the system and it's sealed off but good requiring coils and hose replacement

Earle Horton wrote:

> The problem is insufficient freon in the system. Fixing it is a two step
> process. (1) Find the leak. (2) Evacuate the system and fill it with the
> exact amount of refrigerant required.
>
> If you were a redneck shade-tree mechanic, you might get one of those
> twelve-ounce cans of freon, that comes with its own recharge hose, and fill
> the system until you thought it was working properly. This might work, but
> for long-term satisfaction you have to find and fix that leak.
>
> Earle
>
> "L.W. (ßill) Hughes III" > wrote in message
> ...
> > Your low pressure switch is disconnecting the clutch because you
> > have less than twenty pounds in the suction side while pumping, it
> > should be between 34 and 38.
> > God Bless America, ßill O|||||||O
> > http://www.billhughes.com/
> >
> > MPClark wrote:
> > >
> > > I have a 97 Jeep Cherokee. Now that it's the summer I want to use my air
> > > conditioning. However, when I turn on the A/C, no cold air is put out
> > > and the compressor clutch cycles on and off, as if it were in defrost
> > > mode. I am sure it is set on max a/c with the fan on high, and still
> > > the clutch cycles on and off. I also checked the pressure of the Freon
> > > and that is where it's supposed to be. I was thinking it might be a
> > > relay of somesort that controls the clutch, maybe it is stuck it the
> > > defrost position? Any help would be greatly appreciated.
> > >
> > > --
> > > MPClark

Except we know all air conditioning systems leak with every
vibration of the engine, since the early eighties when the manufacturers
switched to O ring connections: http://www.billhughes.com/OringTool.jpg
God Bless America, ßill O|||||||O


tim bur wrote:
>
> it's against the law to knowly charge a leaking a/c system and leave the charge
> in if the leak is not repaired
> don't try to use a can with sealer it react to o2 to seal the leak so any o2 in
> the system and it's sealed off but good requiring coils and hose replacement

You don't really "know" that a system is leaking until you find the leak.
Your typical shade-tree mechanic may not have the reasoning ability to
connect chronic low pressure with a leak.

All seriousness aside, I fully agree but people are going to do, what they
are going to do, and why do they sell those twelve-ounce cans of freon, that
come with their own recharge hose, anyway?

It took me two cans of sealer/leak detector to find the leak in my Suburban,
after two "certified" mechanics said they had it fixed, and seriously
overcharged me for six pounds of freon. The experience led me to buy a
vacuum pump and gauges, and almost to come out of retirement. The sealer,
leak detector, and oil were all leaking down the drain from the rear air,
onto the ground. ;o)

Earle

"tim bur" > wrote in message
...
> it's against the law to knowly charge a leaking a/c system and leave the
charge
> in if the leak is not repaired
> don't try to use a can with sealer it react to o2 to seal the leak so any
o2 in
> the system and it's sealed off but good requiring coils and hose
replacement
>
> Earle Horton wrote:
>
> > The problem is insufficient freon in the system. Fixing it is a two
step
> > process. (1) Find the leak. (2) Evacuate the system and fill it with
the
> > exact amount of refrigerant required.
> >
> > If you were a redneck shade-tree mechanic, you might get one of those
> > twelve-ounce cans of freon, that comes with its own recharge hose, and
fill
> > the system until you thought it was working properly. This might work,
but
> > for long-term satisfaction you have to find and fix that leak.
> >
> > Earle
> >
> > "L.W. (ßill) Hughes III" > wrote in message
> > ...
> > > Your low pressure switch is disconnecting the clutch because you
> > > have less than twenty pounds in the suction side while pumping, it
> > > should be between 34 and 38.
> > > God Bless America, ßill O|||||||O
> > > http://www.billhughes.com/
> > >
> > > MPClark wrote:
> > > >
> > > > I have a 97 Jeep Cherokee. Now that it's the summer I want to use my
air
> > > > conditioning. However, when I turn on the A/C, no cold air is put
out
> > > > and the compressor clutch cycles on and off, as if it were in
defrost
> > > > mode. I am sure it is set on max a/c with the fan on high, and still
> > > > the clutch cycles on and off. I also checked the pressure of the
Freon
> > > > and that is where it's supposed to be. I was thinking it might be a
> > > > relay of somesort that controls the clutch, maybe it is stuck it the
> > > > defrost position? Any help would be greatly appreciated.
> > > >
> > > > --
> > > > MPClark
>

MPClark did pass the time by typing:
> I have a 97 Jeep Cherokee. Now that it's the summer I want to use my air
> conditioning. However, when I turn on the A/C, no cold air is put out
> and the compressor clutch cycles on and off, as if it were in defrost
> mode. I am sure it is set on max a/c with the fan on high, and still
> the clutch cycles on and off. I also checked the pressure of the Freon
> and that is where it's supposed to be. I was thinking it might be a
> relay of somesort that controls the clutch, maybe it is stuck it the
> defrost position? Any help would be greatly appreciated.

Without actually looking myself it sounds like your slightly low
on refrigerant. That's normal for a system as old as yours. My 93 ZJ
required a kick in the arse (3oz) back in 2000 or so and actually
might need a checkup, hasn't gotten that hot yet.

There are two sensors in the AC system. A low pressure and a high
pressure. the low one is located on the accumulator bottle, the
high one on the ac pump output.

Be careful about how you measure pressure, a correct reading depends on
outside temperature also. My guess is your at the very low edge of
the scale. Also remember to correctly get the pressure you need
to have the compressor running. That's done by jumpering the harness
to the low level switch and settign the AC on max/recirc. Both the hoses
going into the cab should be cold to the touch. If one is cold and the
other warm then your low (or very overfilled). Always trust the pressure
gauge.

If your not familiar with servicing AC systems it might be best to let
a local shop do the work. Around here it's about 90$ for an AC system
service.

For those that quote laws.. here is the EPA read
http://www.epa.gov/ozone/title6/609/recharge.html
The legality depends on the state (or country) you live in.


--
DougW

Alright, I went back to check all of that. After letting the engine and A/C run for several minutes, I checked the pressure to be just about 40. Then I felt the lines: the two going into the cab are slightly warm, the one going into the compressor is also slightly warm, and the line coming out of the compressor is too hot to touch. It's confusing me because whether there is a leak or not, the pressure is where is should be, so low pressure shouldn't be a problem I would think.

It could be a defective low pressure switch, disconnect it and jump
the plug:
http://members.cox.net/wilsond/Fixes...essure-low.jpg It just
unscrews if you need to replace it, no pressure will be lost.
God Bless America, ßill O|||||||O
http://www.billhughes.com/

MPClark wrote:
>
> Alright, I went back to check all of that. After letting the engine and
> A/C run for several minutes, I checked the pressure to be just about
> 40. Then I felt the lines: the two going into the cab are slightly
> warm, the one going into the compressor is also slightly warm, and the
> line coming out of the compressor is too hot to touch. It's confusing
> me because whether there is a leak or not, the pressure is where is
> should be, so low pressure shouldn't be a problem I would think.
>
> --
> MPClark

MPClark did pass the time by typing:
> Alright, I went back to check all of that. After letting the engine and
> A/C run for several minutes, I checked the pressure to be just about
> 40. Then I felt the lines: the two going into the cab are slightly
> warm, the one going into the compressor is also slightly warm, and the
> line coming out of the compressor is too hot to touch. It's confusing
> me because whether there is a leak or not, the pressure is where is
> should be, so low pressure shouldn't be a problem I would think.

The compressor output line will always be hot. The return line from
the condenser (little radiator in front of your radiator) will be cooler.
That line runs back to the accumulator/expansion valve and after that should
be cold, that runs into the cab where it goes through another coil called
the evaporator, then back into the engine bay and to the compressor.

If you grasp the line going from the accumulator into the cab it should
be darn cold/freezing. The line coming out of the cab to the compressor
should also be cold (nearly as cold as the line going in, but not quite)

When checking pressure or filling you need to have the compressor
running all the time, you do that by jumpering the lowside cutout
harness with a bit of wire.

40psi is "normal" for about 75deg outside temp.

General charge chart.
F Lowside psi
65 25-35
70 35-40
75 35-45
80 40-50
85 45-55
90 50-55
100 50-55
105 50-55 (this is where r134a peters out)

The shops measure from the high side.. BE CAREFUL,
high side is HIGH.

F Highside psi
60 120-220
70 140-240
80 170-260
90 200-300
100 230-340
110 270-390

Your description tells me it's low on gas. But don't add a whole can.
only add a bit at a time till the system starts cooling down.

One of these helps for the low side work
http://tinyurl.com/7fsmc


--
DougW