Ac....

[SHOtimer]

So, my AC will work great and cold if it is around 70 or below. However, once it hits the high 80's and into the 100's (like it is today) the AC refuses to get cold.

When I engage the AC the clutch will engage and the AC will cycle, but it will have a heavy load on the engine (unlike when it is in the 70's, i won't feel it) - and in town it will barely get cold. Sitting a light the car will lurch when the compressor cycles, because it is causing such a load.

Today I was doin about 75-80 (100 degrees outside) - with the AC on Max and it was cycling, it would start to get cold then cycle, and go warm, then cycle and start to get cold...then cycle again. This whole time I can really feel the change on the motor while it cycles.

The entire AC system as about 10k on a new Ford compressor, new 'VOV' orfice tube, new accumulator, and all new O-rings.....

Any thoughts?

Doug

 

[Zap]

Do you know how long the clutch cycles on for? If the air is only somewhat cold when it is cold, then I would suspect low charge.... however, you may also need to adjust (or have a faulty if reused) low pressure cutoff switch. The evaporator could be freezing up if the compressor isn't cutting out at the right time.

 

[SHOtimer]

I don't think it is possible that the evaporator is freezing up...it never gets that cold. I replaced the low pressure switch with a brand new Ford piece...and had no change.

I am saving up some beans to take it to an AC shop - however I see that as a last resort....

I prefer being the only one to mess with my SHO.

Doug

 

[1993MTXSHO]

Dunno if this will help but I had trouble with mine and didnt want to deal with it. Mine would work at idel but as soon as the car was under a load the compressor would kick off. Changed out the CCRM and bingo works great now

 

[SASHO91]

How many times is the comp. cycling? rule of thumb- 3 times per mintue.

Im wondering if its a sensor causing this.... the ambient temp. sensor or maybe the coolant temp sensor for the EATC...

any way you can just get the a/c shop to run the pressures on it?

What type of system is it? Im assuming its going to be a R-134a as you put "new" stuff in...

 

[SHOtimer]

I don't think it is either one of those sensors - because it isn't as if the AC is making cold air and the EATC is mixing it with hot air - it isn't making cold air.

The compressor is supposed to cycle 3 times per mintues....even when it is 100 outside?

Also, she is a '95 - always been R134a.

Doug

 

[SASHO91]

yep even with it 120 outside...

you may be low on frion....

if you can, try to get the readings....

 

[SHOtimer]

Well, it is gonna take a week or two to get the readings.

I was under the assumption that because the compressor was putting a large load on the motor that the pressures inside the system were high. Wouldn't that negate the possibility of a low charge?

Doug

 

[Zap]

If the pressures were too high, the high pressure cutoff switch would indeed stop the compressor.... Being a factory system, you will have a HPCOS installed. A number of retrofits often leave the sensors out. Completely forgot about it. The extra high temperatures will allow the problem to manifest more quickly/more often, too. The higher temperature will increase the pressure (hence why A/C is less effective at high temperatures).

At any rate, if you're going to be doing A/C work (and prefer a shop to not touch the car), Harbor Freight has a nice set of gauges with hoses in a case for about $40. Well worth the investment, and you will be able to tell the story immediately and adjust appropriately from there.

The pressures can indicate low/high charge, blockage, misadjusted cutoff, and normal operation depending on what the high and low side show.

 

[SHOtimer]

Right. I am wondering if high pressures are my problem, and why the compressor is being turned off before it actually gets the R134a cold.

What is the HPCOS? I don't think I completely take what you are saying in the first paragraph.

Well, I'm not gonna have the shop take the car apart (I can do that part well enough on my own) - but I certainly will take it there to figure out what is goin on...and for the evac/recharge, if that is necessary.

I was told it is possible that their is air in the system (when it was charged after I redid the system) they vacuumed it for quiet awhile before they recharged. But, that the air could be expanding with the hot temperatures, causing the problem and that a flush/recharge could remidy the situation.

Doug

 

[Ishodu]

I would get the pressure checked on both sides and see where your at. HPCOS I think he is referring to High Pressure Cut Off Switch.

 

[Zap]

If the system is overcharged, as it runs the pressure will increase to a point above where it should be, and the switch will detect overly high pressure and stop the compressor until it has lowered (in order to prevent a line from rupturing).

Air in the system could cause the pressure problem... If a system is charged to weight, and the air hasn't all been removed, there will be an overcharge. If the system is charged to pressure and there is air, it won't cool effectively.

Checking the pressures will indicate the problem, and if they are too high, removing some of the refrigerant until they are correct for the ambient temperature and then checking the air temperature coming out of the vents will indicate if the system is then properly charged. If the pressures are correct, but the cooling is ineffective, air (or something else, such as excess oil charge) is present.

 

[SHOtimer]

Ok - well sounds like I need to visit an AC shop when the system is acting up and find out what is going on internally within the system.

What I have noticed is the problem is heat. To be more specific - if I start the AC in the morning - when it is cool - it will be freezing. If I keep it on I can drive through 100 degree wheather and it will stay freezing. However, if I stop for food and let the car sit for 20-30 min in that temp....I will never get the cold air back because the refrigerant will get so saturated with heat that it won't be able to cool back down again. This is at highway speed BTW.

So, I guess the problem could be as you said - an overcharge, undercharge, air in the lines, or excess oil.

When I put the system together I put about 7oz's of oil in it - which is what is reccommended.

When the system was charged it was done in about 60 degree weather - the tech weighed the R134a canister untill the proper weight of it had been sucked into the system - and he verified that the pressure were good. This of course was after he vacuumed it. - I was standing there watching.

Doug

 

[rangerj]

You added 7 ounces of oil to the system? Was the old oil cleaned out of the system before you did this? As correctly stated above the pressure readings are the first step in diagnosing A/C problems. Guessing and simply replacing parts is not the best way to go. What else was replaced the last time you serviced the A/C system?

Do some basics while you are waiting to get the system serviced. Check for any leaks by looking for black oily residue on the condenser core (in front of the radiator), and at all connections, and at the front of the compressor (behind the clutch and clutch coil assemble (try a mirror and a light). Check the clutch gap for approximately .035 gap, or look up the specified gap for your model year.

When the system is working the high pressure line should be hot and the low pressure line should be cold.

The symptoms you describe bring to mind several possible problems. The pressure readings, temperatures out of the center dash vent, and the cycle times would help in making a diagnosis. HVAC thermometers are inexpensive and available at most auto parts stores.

Question for all forum members.
Would it help if some of us experienced in A/C matters posted a list of the A/C components, how threy work, and how to diagnose and repair problems with each of the components? I know most of this information is in the past posts, but I think it would help if it was accumulated in one place. Any suggestion? Anybody interested? It is that time of year.:wave:

 

[SHOtimer]

You added 7 ounces of oil to the system? Was the old oil cleaned out of the system before you did this? As correctly stated above the pressure readings are the first step in diagnosing A/C problems. Guessing and simply replacing parts is not the best way to go. What else was replaced the last time you serviced the A/C system?

Do some basics while you are waiting to get the system serviced. Check for any leaks by looking for black oily residue on the condenser core (in front of the radiator), and at all connections, and at the front of the compressor (behind the clutch and clutch coil assemble (try a mirror and a light). Check the clutch gap for approximately .035 gap, or look up the specified gap for your model year.

When the system is working the high pressure line should be hot and the low pressure line should be cold.

The symptoms you describe bring to mind several possible problems. The pressure readings, temperatures out of the center dash vent, and the cycle times would help in making a diagnosis. HVAC thermometers are inexpensive and available at most auto parts stores.

Question for all forum members.
Would it help if some of us experienced in A/C matters posted a list of the A/C components, how threy work, and how to diagnose and repair problems with each of the components? I know most of this information is in the past posts, but I think it would help if it was accumulated in one place. Any suggestion? Anybody interested? It is that time of year.:wave:

When I rebuilt my motor last summer I replaced the AC system while I had it apart. I installed a new Ford compressor (complete), a new orfice tube, a new accumulator, and had the condenser pressure tested and flushed. I also installed all new O-rings on the system. At this time I distributed 7oz's of oil throughout the system before I took it to the shop to have it vacuumed and charged. - So, their really was no old oil to speak of in the system, except what was in the evaporator - the AC shop said I shouldn't count on much being in there at all.

So, the entire system has only about 10k on it.

I think that a sticky with all that information would be a great idea.

Doug

 

[rangerj]

Another thought. Make sure the radiator fan comes on when the A/C is on. There is a thermal sensor in the evaporator core that also should be checked. I'm looking for the test proceedures and will post them.

 

[SHOtimer]

Another thought. Make sure the radiator fan comes on when the A/C is on. There is a thermal sensor in the evaporator core that also should be checked. I'm looking for the test proceedures and will post them.

I have verified that the fans are always on when the AC is on. That was my first thought. Ok, thank you.

Doug