Air Conditioning Question

[Bluerauder]

Took my Marauder into the dealer yesterday to have the A/C checked. Didn't seem to be putting out cold air like it used to. Of course, it has been unseasonably cool here through May. Now that June is heating up and the humidity is rising, the A/C issue has been more noticeable. I went through the same thing just about a year ago. Recharging the A/C with R-134 (?) last time worked until now. :D

Service tech says pressure readings are good and that the temp at the vents is 32 degrees. :rolleyes: No way. I had the service manager come out to the car and tell me if it felt like 32 degrees to him. Nope !!! I suspect it is closer to 60-65 degrees max. Couldn't leave it there for another full day, so I decided to reschedule and check it out. On the way home last night, it took a full 25 minutes before the interior started to cool noticeably. On the way home tonight, the auto blower stayed on max for the entire 40 minutes trying to get the interior to 68 degree and it is only 85 today.

I suspect a bad compressor. But the tech says pressures are fine. Maybe he can't read pressures or thermometers. :rolleyes:

Any ideas on what the real problem is?? :confused:

P.S. I don't know how you folks with the charcoal interiors can stand the heat. I had a Silver/Gray Sable as a loaner yesterday with the charcoal leather interior and it was scorching inside. My Light Flint is much, much cooler.

[twolow]

P.S. I don't know how you folks with the charcoal interiors can stand the heat.
Lots and lots of tint :)

[Smokie]

I know A/C. First off it is very unlikely that your vent puts out 32 degree air since that is the temp at which water freezes, 36-40 degrees on an 85* day with high humidity would be normal. I recommend you buy a pocket thermometer such as the ones A/C tecnicians use and put it in the vent (they are inexpensive and very accurate)

Does your A/C produce water that drips under car while A/C is running? It should.
Does your suction line going back to compressor sweat and it is very cold to the touch? It should. (Suction line is the larger diameter hose or pipe from the outlet of the evaporator back to compressor)

Don't have someone just tell you the pressure is ok, ask if they are checking both the low side and high side and ask what those pressures are.

Typical hot day your high side should be between 190--250 psi, your low side at a high idle should be no less than 35 psi and no more than 45 psi. Good luck.


P.S. Freon does not wear out, if freon was added to your system YOU HAVE A LEAK. it is illegal in Fl. to recharge a leaky system, it must be repaired (find and Fix the leak)

[Ricka11]

Hey Bluerauder:

I owned a 93 Mazda MX6 (Ford Probe) and had a similar A/C problem. Well after several trips to the shop and many hundreds of dollars later, the problem was finally corrected, a bad Expansion Valve. Once that was replaced, A/C worked great!
.
Also, that was my Black Marauder parked under the cover over at the L/M dealership. Thanks for the MM.Net card!

[Bluerauder]

Does your A/C produce water that drips under car while A/C is running? It should.

Don't have someone just tell you the pressure is ok, ask if they are checking both the low side and high side and ask what those pressures are.

It was dripping and puddling 2 weeks ago when the rear tires were changed; but I don't see it anymore. :(

They did say that they checked the high and low side pressures; but I didn't ask what they were 'cause I wouldn't have known what was reasonable. :rolleyes:


Also, that was my Black Marauder parked under the cover over at the L/M dealership. Thanks for the MM.Net card!
Rick, sorry I didn't recognize your car. I forgot to write my screenname on the bottom of the card when I gave it to the service manager. He said that he would get it to you. Seems that it worked 'cause you figured out who is was !!! :up:

[ncmm]

Lots and lots of tint :)
plus a reflective window shade for the front window when parked

otherwise. . . :sweat:

[Fourth Horseman]

P.S. I don't know how you folks with the charcoal interiors can stand the heat. I had a Silver/Gray Sable as a loaner yesterday with the charcoal leather interior and it was scorching inside. My Light Flint is much, much cooler.

Garaged as much as possible. Shade is my friend. :)

[SergntMac]

I know A/C. First off it is very unlikely that your vent puts out 32 degree air since that is the temp at which water freezes, 36-40 degrees on an 85* day with high humidity would be normal. I recommend you buy a pocket thermometer such as the ones A/C tecnicians use and put it in the vent (they are inexpensive and very accurate)

Does your A/C produce water that drips under car while A/C is running? It should.
Does your suction line going back to compressor sweat and it is very cold to the touch? It should. (Suction line is the larger diameter hose or pipe from the outlet of the evaporator back to compressor)

Don't have someone just tell you the pressure is ok, ask if they are checking both the low side and high side and ask what those pressures are.

Typical hot day your high side should be between 190--250 psi, your low side at a high idle should be no less than 35 psi and no more than 45 psi. Good luck.


P.S. Freon does not wear out, if freon was added to your system YOU HAVE A LEAK. it is illegal in Fl. to recharge a leaky system, it must be repaired (find and Fix the leak)
Javier knows A/C, take this 411 to the bank.

[MitchB]

Yes you can have discharge temps below 32 degrees, although the system is not designed to run this way. Your car has a fixed orifice instead of an expansion valve. The system is designed to cycle the compressor. Cycling is controlled by a low pressure switch located in the suction side of the evaporator. As the load or cooling demand increases, the compressor increases its cycle 'on' time. Humidity imposes great loads on the system.

Anyway, you would be surprised if you could see the diagnostic routines used to evaluate and diagnose system performance. They are all in Ford's shop manuals and should be followed to some degree by your service tech. It is rather difficult to troubleshoot a system remotely, especially if you do not have a mechanical feel for what you are looking at. However, do not let your dealer tell you nothing is wrong if you know with certainty the system is not working properly. Two important things to keep in mind: 1. If it is determined that the solution to your cooling problem is, at least in part, to add freon, then obviously you have a leak! Point is, any system that leaks also looses oil. Reduced oil in the system will shorten compressor life. 2. The compressor needs the low temperature freon return vapor for cooling. As a system looses freon, the first thing that happens in addition to reduced system capacity is the compressor starts to overheat. 1 and 2 above usually occur together and work synergystically to really shorten compressor life. So don't accept a quick look-see by a service tech who tells you its OK. System pressures alone do not tell you how the system is working.

BTW, I have worked on HVAC systems of all types for many years, have a federal license and an engineering background. It is truly amazing and sad to see the level of incompetence in the field. And not only in automotive field. Home installers do not do much better.

Oh, one other thing, if your tech does not use an infrared gun to measure the temp of the system at varoius points, then he at least better follow the shop manual's performance guidelines and parameter limits closely.

Mitch

[Dennis Reinhart]

Actually the car has a CCOT system constant cycling orfice tube. I have over twenty years experince with A/C I have never seen 32 degree air coming out the vent, things to consider, are do you run the car in AC or Max AC, if its in AC you are out of the recirculate mode, what happens then is a blend air door will open up and and you will blend out side air with cold evaporator air, in high humidity you will see frost coming out of the vents, in this mode you loose peak cooling, if the compressor looses a Teflon ring the Low side will be high, if the orfice is plugged the low side will go low, the high side will be higher than normal, on a 90 degree day a normal gauge reading is 40 on the low side 250/275 on the high side, if the A/C is low the compressor will cylce on and off very frequent with the blower in high, with a fully charged A/C with the blower on low its normally to see it cycling on and off this keeps the evaporator from freezing up, if the A/C is over charged little as 4 OZ can effect cooling out put, call me any time if I can help.

[Smokie]

Service tech says pressure readings are good and that the temp at the vents is 32 degrees. :rolleyes: No way. I had the service manager come out to the car and tell me if it felt like 32 degrees to him. Nope !!! I suspect it is closer to 60-65 degrees max.
I suspect a bad compressor. But the tech says pressures are fine. Maybe he can't read pressures or thermometers. :rolleyes:

Any ideas on what the real problem is?? :confused:

Assuming that the you really had a vent discharge of 32 degrees, that should have alerted the tech. of a PROBLEM, because it is NOT a normal discharge temp. If you are low on gas and have a partially frozen evaporator it is possible for the air passing thru the ice at slower than normal speed to loose so much heat the temp might drop to 32 degrees, however it is a vicious circle where the slower air flow and freezing evaporator eventually the pressure on the low side is so low that the low pressure cut-off will turn off the compressor.

I am not in any kind of disagreement with information given to you by the previous members...only with the lying or ignorance from the dealer that told you there is no problem with your A/C.

[Bluerauder]

Thanks to all that responded with all the great information. :up: I am still sorting through this. :rolleyes:

Assuming that the technicians statement of high and low side pressures being in the normal range are accurate and that the A/C is fully charged. And that he got a 32 degree vent temperature (which I kinda doubt). Then, I will run it and listen for compressor cycling with the blower on both the high, then the low settings. :D Will also pick up one of those thermometers if they have them at Auto Zone.

Based on what I think I have heard here, my evaporator may be freezing up and the tech didn't run it long enough to see the pressure drop on the low side. If so, what is the fix ?? I am still under warranty for another 15,000 miles or 16 months. Of course, I'll punch out on miles first -- probably by next June.

[Dennis Reinhart]

Thanks to all that responded with all the great information. :up: I am still sorting through this. :rolleyes:

Assuming that the technicians statement of high and low side pressures being in the normal range are accurate and that the A/C is fully charged. And that he got a 32 degree vent temperature (which I kinda doubt). Then, I will run it and listen for compressor cycling with the blower on both the high, then the low settings. :D Will also pick up one of those thermometers if they have them at Auto Zone.

Based on what I think I have heard here, my evaporator may be freezing up and the tech didn't run it long enough to see the pressure drop on the low side. If so, what is the fix ?? I am still under warranty for another 15,000 miles or 16 months. Of course, I'll punch out on miles first -- probably by next June.
If the evaporator starts to freeze up the low side pressure will drop, when this happens the the pressure switch see that and cycle the compressor off, if the the sensor goes bad, and they some times do, the evaporator can freeze over and no air will pass through it just like the old freezers years ago before defrost elements and timers were added, but even in this case if the evap is frozen up, the low side will will be abnormally low, thats where experince counts when it comes to proper diagnoses.

[Smokie]

There are things that you can do without expensive equipment to have a reasonable idea what the problem is.

First off all testing and checks need to be done with A/C on MAX A/C setting with temp control set at 60* (this is important) set the fan speed wheel to max by hand so you disengage Auto Fan.

The only fancy tool you need is the little pocket thermometer I suggested and the palm of your hand.
Set thermometer in the vents in the middle of your dash and observe temp. drop. Do this during hottest part of the day, not at night (important)

Within 5 minutes of starting A/C you should notice water dripping under car from evaporator.
The low pressure line right at the compressor should be VERY cold and sweating after 5 minutes.
If you notice that the discharge speed of the air coming out of vent slows down and becomes very cold (below 35*) your evaporator is freezing.

Is not important that you diagnose exactly what the cause of the problem is, it can vary. what is important is that you recognize that there is a malfunction.

On a hot day, 85 or above, your A/C will drip water nonstop, your discharge temp. will fluctuate between 36-45, remember it is normal for compressor to cycle on and off so temps will fluctuate.

Best of luck.

[worksuxxx]

Let off the accelerator pedal. WOT shuts off A/C :banana2:

[Bluerauder]

Had the dealer take another look at the A/C system again while it was in for the wiper/washer problem. :D

Pressure readings were 200 psi High Side, 42 psi Low Side, and 33 degrees at the outlet vents. I now have this documented with the dealer and the service rep with three visits and readings on the service sheet. The car A/C was blowing cold on the way home tonight and it felt alot better. However, the outside temperatures are about 10 degrees lower today than for the last week or so. Humidity was also down; but I am still not noticing much condensation under the car if any like I used to.

Understand that the High Side should be in the 250 psi range and I let the service manager know that. His technician insists that the readings are within spec. :rolleyes:

[Smokie]

The pressure on the low and high side vary with ambient temperature, humidity and engine rpm's, also the vent temp. can vary, I find it unusual that it would be 33 degrees on a hot humid day such as 85* or above and 80% humidity or higher.

If your vent discharge temp. is in the low 30's while your fan is on med-high or high, your car has to cool down and actually on a cloudy day or at night get quite cold inside the car.

I would recommend getting a thermometer to put in the vent and monitor the temp. When you feel uncomfortably warm and the fan is on medium or faster, I guarantee you that your vent temp will be above 50 degrees.

[MitchB]

I'll say it again, the way you evaluate A/C performance is by measuring certain performance parameters and comparing your observations to an allowable range for these parameters given the conditions the observations were made under. Take just one important set of measurements: for a given ambient temperature and humidity, your pressures need to be within a certain range, with the blower on a given speed, your duct discharge temp need to be within a certain range, and with ambient temp, humidity and for a set blower speed, your compressor needs to have a duty cycle within a certain range. In other words, the compressor 'on' time must be within a given range. I verify these performance parameters for any A/C system I work on. There are tables in the shop manual that give you the variables and allowable ranges. Taking measurements and comparing them to these tables is the only way you can determine whether or not your A/C system is functioning normally. It does not sound like your dealer is following Ford's own service proceedures.

Mitch

[DEFYANT]

Thanks for all the info here! I have a feeling this will be dug up in the future!!

[STRAN]

I just read through it.

[RF Overlord]

Having the same trouble as Pat did way back then...air from the vents is only a few degrees below ambient and the compressor is short-cycling. Sounds to me like low refrigerant...I don't have the tools or gauges to properly work on HVAC systems, so Phoebe is going to the doctor tomorrow. Tirrell Radiator in Hyannis.

[2vmodular]

you do not want the evaporator temperature under 32 degrees. you will get ice forming on the evaporator if you go that low which will restrict air flow.

these cars do have a large amount of extra a/c capacity during the mild northeastern united states summers. if you apply power directly to the compressor 100% of the time, you can easily turn your evaporator into a solid block of ice as long as the ambient temperature isn't extreme.

[cougar9150]

Kind of having this same problem. Not cooling down very well during the heat of the day but seems to work fine once the outside temps are in the low 80s. Had it running out front for about 20 minutes, the compressor was on 100% of the time after cycling during the 1st 2-3 minutes. It did have a very noticeable puddle under the car from the AC dripping but none of the lines were really cold to the touch or sweating and the air out of the vents isn't really that cool. The Fan was running the whole time, air on max, and set to 60.

This is out of my expertise and comfort zone so it looks like the shop will be taking a look at it.

[NATEHAWK]

Yes you can have discharge temps below 32 degrees, although the system is not designed to run this way. Your car has a fixed orifice instead of an expansion valve. The system is designed to cycle the compressor. Cycling is controlled by a low pressure switch located in the suction side of the evaporator. As the load or cooling demand increases, the compressor increases its cycle 'on' time. Humidity imposes great loads on the system.

Anyway, you would be surprised if you could see the diagnostic routines used to evaluate and diagnose system performance. They are all in Ford's shop manuals and should be followed to some degree by your service tech. It is rather difficult to troubleshoot a system remotely, especially if you do not have a mechanical feel for what you are looking at. However, do not let your dealer tell you nothing is wrong if you know with certainty the system is not working properly. Two important things to keep in mind: 1. If it is determined that the solution to your cooling problem is, at least in part, to add freon, then obviously you have a leak! Point is, any system that leaks also looses oil. Reduced oil in the system will shorten compressor life. 2. The compressor needs the low temperature freon return vapor for cooling. As a system looses freon, the first thing that happens in addition to reduced system capacity is the compressor starts to overheat. 1 and 2 above usually occur together and work synergystically to really shorten compressor life. So don't accept a quick look-see by a service tech who tells you its OK. System pressures alone do not tell you how the system is working.

BTW, I have worked on HVAC systems of all types for many years, have a federal license and an engineering background. It is truly amazing and sad to see the level of incompetence in the field. And not only in automotive field. Home installers do not do much better.

Oh, one other thing, if your tech does not use an infrared gun to measure the temp of the system at varoius points, then he at least better follow the shop manual's performance guidelines and parameter limits closely.

Mitch



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[2vmodular]

harborfreight has a cheap set of a/c manifold guages onsale for $29.99.

http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html

discharge & suction pressure readings are really useful when trying to troubleshoot an a/c system.

[Bluerauder]

Thanks for all the info here! I have a feeling this will be dug up in the future!!

Yep, 6 years and back from the archives.

[nwilkes]

Im having the same issues. When its below 80 degrees outside the interior gets cold. Over 80 degrees and i end up opening windows cause it feels like i have a hair dryer blowing in my face. Time to go to the shop and spend some more $$$.