a/c clutch cycles

[warrior24]

I have 92 ranger and the clutch keeps cycling on and off I check the psi with a/c on full and I get 44psi low side. I tested power at the compressor and I get 14v constant. So I guess that means my clutch is ok. I noticed that on the accumulator (clutch cycling switch) the terminals have green gunk on them. Should this green stuff be there ? I am thinking for anti corrosion when the thing starts to sweat. So if I have proper pressure why is it cycling? Do I need to get professional gauge set rent or own ? I have read some stuff about jumping the clutch cycling switch or compressor but i am not sure on which one. Guess I just wanna fix my a/c as it is starting to heat up Here in AZ.

 

[warrior24]

Update I jumperd the cycling compressor switch harness, so compressor stayed on then checked pressure 20psi and it was low so I added r-134 and used a hole can and un-jumpered the harness and plugged the harness back in and now the compressor stays on. Now I have 26 psi, I think because the compressor kept cycling it made the pressure stay up ( it was off more then it was engaged) , because I checked the pressure with the air off and I would get 64 psi, which led me to believe that I was getting a sorta false positive reading. I wonder if I had the professional gauges it would have had this problem. I hope my explanation makes sense please feel free to enlighten me if I am wrong or make no sense as I often do.

 

[skippy]

Pressures are checked with the compressor operating.If you had to add refrigerent,you have a leak.With system off and pressures allowed to rise,check all connections with soap/water solution,the leak shoud blow you a bubble.Don't forget to check the refrigerant gage connections.

 

[LittleHorse]

The pressure will be higher when it's off because the pressures will equalize between the high and low sides. Then when it first starts, the high side pressure will climb and the low pressure will drop real quick and then start climbing as the system stabilizes, and eventually settle on a constant value, assuming the load is constant and large enough to keep the system on line.

26psi still corresponds to a 30° evaporator, which is pretty low for an air conditioning system or anything that doesn't run a defrost cycle. Really you want it to be about 37-42°, which would be 32-37 pounds.

Do our trucks have a sight glass in the refrigerant lines? I haven't messed with mine enough to notice one. If it has a sight glass, you could charge it until there's no longer any visible flashing (bubbles). Then depress the suction line valve for just a little burst and make sure it's all gas coming out. If there's liquid drops, you've over charged it.

The most reliable way to charge a car system is to evacuate it and then weigh it in according to manufacturer specs.

 

[warrior24]

Ok I am gonna rent a vacuum from checkers and gauge set to do it right . My understanding is put the vacuum on for 3 hours to get all moister out. Then leave it with vacuum to see if it stays at that for 30 min. Then if vacuum pressure changes you have a leak. Then add r-134 until I get 32-37 psi depending on lowest temp reading from thermometer. I have one question how much psi should the high pressure read?

 

[Beanmachine7000]

It sounds like you described a correctly working A/C system to me, your compressor will cycle on and off, and 44 psi is just about perfect...

 

[LittleHorse]

Ok I am gonna rent a vacuum from checkers and gauge set to do it right . My understanding is put the vacuum on for 3 hours to get all moister out. Then leave it with vacuum to see if it stays at that for 30 min. Then if vacuum pressure changes you have a leak.

correct up to there...

Then add r-134 until I get 32-37 psi depending on lowest temp reading from thermometer.

not really...what you want to do is use a balance/scale accurate down to an ounce. Find out what the refrigerant capacity of the system is. Place the full can on the scale while you're charging and "weigh in" the correct amount of refrigerant. You'll probably empty at least two cans in the process. At this point, you'll be charged and your pressures should be good.

The pressure being low or high is just a symptom of other issues such as being undercharged or an unbalanced load, or mechanical problems. You can't accurately charge by pressure without knowing exactly that your system and load are perfectly matched at that moment.

The equipment I work with is charged by the sight glass, because it will be clear at the point it's ideally charged. It often requires adjustment though based on ambient temperatures, etc. Also, systems using a thermostatic expansion valve are much more tolerant to charge variations than a typical orifice tube systems seen in automotive and less expensive residential systems using R-22.

I have one question how much psi should the high pressure read?

The highside pressure will vary according to the incoming air temp to the condenser. The hotter the air, the higher the pressure. It will naturally adjust itself according to achieve the temperature difference it needs to reject the heat it picked up through the evaporator. It's also a function of condenser size, and varies by design.

 

[warrior24]

WOW thanks guys for all the useful info. I have learned something new and I love it when that happens.

 

[skippy]

The pressure will be higher when it's off because the pressures will equalize between the high and low sides. Then when it first starts, the high side pressure will climb and the low pressure will drop real quick and then start climbing as the system stabilizes, and eventually settle on a constant value, assuming the load is constant and large enough to keep the system on line.

26psi still corresponds to a 30° evaporator, which is pretty low for an air conditioning system or anything that doesn't run a defrost cycle. Really you want it to be about 37-42°, which would be 32-37 pounds.

Do our trucks have a sight glass in the refrigerant lines? I haven't messed with mine enough to notice one. If it has a sight glass, you could charge it until there's no longer any visible flashing (bubbles). Then depress the suction line valve for just a little burst and make sure it's all gas coming out. If there's liquid drops, you've over charged it.

The most reliable way to charge a car system is to evacuate it and then weigh it in according to manufacturer specs.

No sight glass.On vehicle systems,weigh in the charge after evacuation.Do leak search and repair first.

 

[IRKillroy]

um, it'd be best to evacuate you system into a container that you'd be able to re-use what you evacuated.... so basically, take it to a shop to get this done as R-134a still does damage to the Ozone....

 

[skippy]

um, it'd be best to evacuate you system into a container that you'd be able to re-use what you evacuated.... so basically, take it to a shop to get this done as R-134a still does damage to the Ozone....

Very good advise.

 

[warrior24]

OK ill do that.

 

[shadetree]

not really...what you want to do is use a balance/scale accurate down to an ounce. Find out what the refrigerant capacity of the system is. Place the full can on the scale while you're charging and "weigh in" the correct amount of refrigerant. You'll probably empty at least two cans in the process. At this point, you'll be charged and your pressures should be good.

I do not know of anyone who uses this method in servicing automobile a/c systems. They fill to system capacity while monitoring pressure, myself included.shady

 

[IRKillroy]

um... anyone who is MACS certified or knows what they are doing will fill it by weight. it's the way it's intended. pressure is relative to atmosphere and temp in the truck...

is this why you call yourself shadetree? because you work under one?

the machines at the A/C shops have the 30lb bottles on a scale, they evacuate the system then hold it for 30 min... then charges it using weight... pressure is only to check if the SYSTEM is working properly, not how much refrigerant is in there.

 

[shadetree]

um... anyone who is MACS certified or knows what they are doing will fill it by weight. it's the way it's intended. pressure is relative to atmosphere and temp in the truck...

Simply not true. It is not necessary on an automotive system. Even home techs use pressure readings for filling the system. The system holds so much refrigerant no matter the outside factors.

is this why you call yourself shadetree? because you work under one?

It doesn't really matter if one works under a tree, in his home garage, or in a million dollar facility, as it has nothing to do with anything as long as the tech has the knowledge, and knows what he/she is doing. I have been doing auto repairs most of my life, and currently own a restoration business. What is your mechanical background?

Being that you are a newbie, Jim frowns on things personal in these forums.

the machines at the A/C shops have the 30lb bottles on a scale, they evacuate the system then hold it for 30 min... then charges it using weight... pressure is only to check if the SYSTEM is working properly, not how much refrigerant is in there.

Maybe where you live, but not all shops do things the same way. There are several ways of achieving the same goal, and they all have the same result.shady