Instead of typing the whole thing over again I will give the link to the original post. I was told to post this over here that maybe someone could guide me in the right direction. I will be checking the system with gauges this Wednesday 8-16-2006 and will post my results but here is the link https://www.ford-trucks.com/forums/5...c-problem.html
If anybody has any info it will be greatly appreciated. More info to come on Wednesday.

 

Until you actually hook up the guages and get real readings, any further postulation is pretty useless as indicated by your first thread. You were advised numerous times what was needed....

Make certain you follow the proper setup (RPMs, MAX AC, and HIGH) and that you note the ambient temp and the center vent temp when you post your readings. If you don't provide complete data, you'll get a lousy diagnosis.

Steve

 

I will post readings sometime tomorrow outside temp and all the good stuff thanks for the help it is much appreciated.

 

I checked the system with the gauges today and my readings go as this. With the engine off the low side about 93lbs high side 102lbs. With the enigine running at about 1500 rpm the low side read 150lbs and the high side 205-210lbs. It is 100 degrees outside at the time of making these readings. This would lead me to believe that the orifice tube or dryer is the problem. Is this correct or am I way off ? Whatever it is I am not going to like.

 

Are you certain that you had a low side of 150psi???? Those readings are impossible - typo or misread maybe?

The low and high side readings should be the same within several minutes of the system being shut down.


Also need the center vent temp.

Incomplete data is not going to help.....You have to provide ALL of it.

Steve

 

The center vent temp was around 50 degrees after letting the air run 3-4 minutes my truck was sitting in the garage and it was about 100 degrees outside. I took 2 reading and they read the same each time. With the car off the low side read 93 and the high side read 102 I had somebody tell me that the orifice tube or dryer was the problem not letting it suck down the low side. Yes the readings are about the same after shutting the car off just like they were before starting the car. Would low on Freon cause this problem? What numbers on the gauge do you actually look for to know if you are low on freon?

 

Ok I feel like a idiot now. The gauges I was using I guess were bad I borrowed another buddy's set and got readings that sound normal. Here is what I got the temp inside my garage where I did the test was 92 degrees the humidity was at 60%. I ran the vehicle for a total of 5 minutes with the A/C at full blast. The first reading I took was before the truck was ever started.
The low side read 86lbs the high side read 99lbs.
The second test was running the truck at a high RPM and my readings were as follows.
The low side would start off between 35-40lbs and as I reved it the pressure would drop to 21-22lbs and the compressor would shut off and it would climb back to 35-40lbs before the compressor would come back on.
The high side would start off between 210-220 as I reved the motor the pressure would climb to 245-260lbs then the compressor would cut off and the pressure would drop back down to 210-220lbs before the compressor would come back on.
If you let the truck sit at idle the pressure would sit at.
Low side 35
High side 225
I then shut the truck off and check the readings they dropped for a second or too then these were the readings.
Low side 63lbs
High side 74lbs
The tempreture off the center vent was reading 47-48 degrees after the truck had been running about 5-6 minutes.
I also wanted to mention one other thing I went to Oreilly and one of the guys that works their part time is a mechanic and he lloked at my truck and said it did not have a high pressure cycling switch just a low one on the dryer I just wanted to throw that in if you needed that info. Thanks again hopefully this is a enough info to diagnos the problem.

 

A high pressure safety cutout switch is supposed to be installed on conversions, but they are often skipped. The lack of one in your system is not a factor in your system's intermittent opperation.

Under the conditions you tested at, those are fairly typical results for an R12>R134a conversion. Nothing to brag about, but pretty typical. Perhaps a minor undercharge, but I wouldn't bet on it. Temperature comparisons between the evaporator inlet and outlet lines would provide a finer definition.

Moving on to the intermittent operation. Since it's pretty unlikely that you would be able to get guage readings during the failure mode, a couple of things may be considered.

1) Posible slipping A/C clutch. Measure the clutch air gap and see if it's too wide.

2) Possible evaporator icing. If this occurs, airflow through the dash will diminish and the little air coming through the vents will usually have a clammy feeling.

3) Possible o-tube icing

4) Possible intermittent failure (internal collapse) of one of the rubber lines.

Gotta leave. BBL.

Steve

 

Now since I have been testing and removing these gauges with the freon that you lose taking the gauges on and off. The compressor is now cycling on and off quite a bit I think that it is low on freon does it sound like it to you?

 

Yes, it does.

Steve

 

The pressures you report and the vent temps you report are within the normal range for an R134a conversion, considering the 93 degree ambient. It is probably warmer than that right in front of the condenser.

If anything, I would say your high side pressures are a little too high. This suggests a slight overcharge rather than an undercharge. You should not think that "more freon" always equals "colder air", as if it were somehow "cold juice" circulating in the system.. Rather, there is an optimum amount of refrigerant in any system. More refrigerant or less refrigerant than optimum will result in higher vent temperatures.

The cycle rate of the fan clutch is very dependent on the temp and humidity of the ambient air, as well as the environment seen by the condensor. Cycling on and off is NORMAL for an orifice tube based system. If the garage cools off, the cycle rate will increase.

It is true that a lower charge also increases the cycle rate, for any given set of conditions. You really should have the proper pressure/temperature/cycle rate charts before you try to "fix" the system by increasing refrigerant charge.

One other thing to note is that your guages remain a bit questionable. The high side and low side guages should read the same with the engine shut off, as the pressures should equalize in the system without the compressor turning.

 

Before this problem started happening the the A/C would put out around 38 degrees at the vent. Is it possible that all these years working so good and now it's overcharged. Yesterday testing it the garage sat at 92 degrees and the compressor was kicking off and on. Is there a place that I can find out specs on this. I feel that it is a little low but you do have a good point that overcharging will not help. Is there any other suggestions out there I open to hear them.

 

The compressor's cycling is a direct function of the cycling switch. If yours is functioning normally (unknown data point, but, for discussion's purpose, we'll assume it is) then it is cutting out at a suction pressure around 22-25 psi and re-engaging around 43-45 psi. Unless the guages are attached and are showing this operating range on the low side, we can only assume that it is cycling as intended (a dangerous assumption).

No. The system cannot magically create more refrigerant as you probably suspect. Since you have now indicated that the system performance was very good previously, we do know that something has degraded.

I also tend to agree with fefarms' assessment that your high side is a little high for the given conditions. This suggests that the condensor is not rejecting sufficient heat due to airflow issues (dirty condensor or radiator fins, or fan/clutch issues) or that there is a restriction in the high pressure side of the system (o-tube or condensor).

I also agree with fefarms in that your guages are not accurate. However, they may be close enough that they're still somewhat useful.

At 92F, the compressor really shouldn't be cycling, especially if at idle. That does suggest a low charge to me. An overcharge cannot produce short-cycling unless there are other system defects.

Steve.

 

I wonder if the 38 degrees you so fondly remember was taken at the same harsh conditions of temperature and humidity? Any air conditioner has the basic function of trying to push heat uphill, so the farther it has to push the heat, the harder it is and the more poorly it performs.

One experiment you can try is to mist your condenser with water as the system is running. This should significantly reduce vent temps. If it does not, something is wrong with the evaporator or orifice tube.

If misting the condenser helps, inspect your fan clutch carefully, inspect the condenser for blockage

You can get a nice chart of refrigerant pressures and A/C clutch cycle rate from Ford's service info. I have the service info for all Ford trucks built in 1996 on CDROM, which I got from an ebay seller for $10.

I'm reluctant to reproduce the complete chart here, because it is copyrighted material. But here is relevant data for your conditions:

Outdoor temp 93 degrees
A/C on "recirc" or "MAX A/C" with max fan speed
windows closed, cabin temp stabilized between 70 and 80 degrees
1500 Engine RPM

High side pressure 240 PSI
Low side pressure cycling between 22 and 52 PSI
Clutch on time 20 seconds
Clutch off time 5 seconds
Center vent temp 45 degrees

This is for a 1996 Ranger system designed for R134a. A conversion would be expected to perform a little worse than this, due to smaller condenser and evaporator.

 

I received this PM from iracekx:

I put the can of freon in a buddy of mine his mechanic told me to spray the condensor when add the can to keep the head pressure down the high side never got over 170. This morning when I drove it the temp was 87 degrees outside and the thermometer that is in the vent read between 32-34 degrees. This afternoon when we were in triple digit temps it was blowing 39-40 degrees so that can of freon seem to fix the problem it never let off the whole 70 miles I drove today.
The other guys probably won't believe it is blowing that cold for a conversion but I know it is so that is all that matters. Thank you again so much for your help and have a great day. P.S coming back from the motorcross track it sure was nice to have A/C again after riding out in the heat. jd