With humidity and heat it is triple digit temp here. I went for a 30 mile drive and came home and my A/C compressor was kicking on and off rapidly. The lowest vent temp I could get while driving was 71 with an infrared kitchen thermometer. I did a little research and pulled the compressor clutch off and cleaned it very well. Had some rust on it. I also cleaned the pulley. Air gap was in line with what my research showed with the one spacer that was in there.

After reinstalling, the clutch was cycling about every 10 seconds. After about a minute of running it went to cycling every 20-30 seconds then it started running constantly. I took it out for another short drive and A/C temp was constant in idle and 40 mph. But it still only registered about 70 degrees. This won't get it in Houston. My system has R34 and a Motorcraft compressor and orifice tube. I guess I could be overcharged or undercharged but ??. I'm taking it to the shop tomorrow. Approximately what should I see ideally on the low and high side for optimum performance. Any thing else I should do based on this post? The compressor is Motorcraft YCC193 and the orifice tube is Motorcraft YG346. Installed about a year ago. A new dryer was not installed. Sandy

 

I dont know the pressure values you are looking for, but, it sounds like it may be under charged based on my previous experiences.
Most auto parts stores have R-134, and a fairly inexpensive filler hose with a gauge that will display the pressure in the system. While it is not as professional as a shop, it has worked very well for me on many different vehicles

 

Thanks puppyf250. I can get it checked for free at the shop. I think it is undercharged also. Sandy

 

System is quite low, for what it is worth. The rapid cycling is tripping the low switch when the pressure drops under about 25psi, this prevents freezing the evap. Pressures are based upon ambient temperatures (yay physics! ), just look for a PT chart for 134A to get an idea.

Consider buying a real seat of gauges and charging it yourself, it is not hard. Yellow Jacket or Mastercool are what I recommend. Pure 134A is $5 for 12 at my Wallymart. The '96 takes three, 12oz cans and a shhhht from another for the last two ounces.

Yours will have to diddle with because not an OE 134A truck, at least you have the FS10 compressor. Not the POS FS6 on my '88. You should consider swapping in a '94-97 HVAC box with the bigger evap and a '94-97 condenser. The entire HVAC box can be swapped quick and is only held in with six bolts. At least clean your current evap, you will be flabbergasted how gross it can be come.

 

Vent temp on MAX fan high was 65 at idle vent temp at 2K RPM was 55

 

Something to remember if you just do the R-12 to R-134 conversion kits you see at places like Walmart. All that is is some adapters to attach the R-134 cans to an R-12 system. It will work for a while, but, from my understanding R-134 molecules are smaller, and it will slowly bleed out over time. That being said, I have done this conversion, and have had several vehicles, including a semi, last for a year or two.

 

Sandy,

i know you are far more versed then me, but is your system switching to defrost at all when you say it is cutting in and out during your drives? It has fallen off my priority list but I still need to trace my leak between the HVAC controls and the blend door actuator.

 

55 degrees while driving? That's pretty good if you're 100 degrees ambient with an old leaky ford cab. Certainly worth checking pressures though, almost like routine maintenance once a year.

 

Not going to defrost. We did put dye in the system so a black light in a few days will tell me if I have a leak. I have it working good now as it was still undercharged on the low side. Regards Sandy

 

System was still low on the low side and we added dye and another can of R134. Driving temp coming home was a nice 47 degrees. I might live through this summer We did add some dye so I will check it with a black light in a few. Regards Sandy

 

Oh I see. I missed the post where you evaluated the system. Stay cool

 

FWIW, and I don't know if this will apply to you but my A/C system in my '93 150 (5.0, A/T) didn't seem like it was up to task. We don't get many oppressive days here in Connecticut, but then, I like my cab cold enough to hang meat in! I tried re-charging the system-it was a *bit* low and that helped a little, but was no where where I wanted it to be.
After suggestions from an A/C tech, I replaced the condenser and the dryer, neither of them are expensive at all...vacuumed down the system and recharged and , BAM...good frigid air now comes from the vents!
YMMV, though...

 

55F driving is good to you? Those temps are garbage, sorry.

 

This

On my 91 I was getting low 40s out of the vent cruising down the highway on a 110 degree day. Running computer duster.

 

@Roger T. Pipe @Hit Man X
@Krisverde

I mentioned above the drive home today was showing 47* on an infrared. Much better than before. It got cold enough to put it back on normal. My BIL shop guy wants me to check for the dye in a few days. The dryer is the original R12 one. I really want to put a new dryer in it. He thinks I may have a leak in the evap. Because of the situation at the shop, I need to do as he ask and wait a few days and see if it is leaking. We are good friends and he is acting in my best interest so I will wait. Then I will get it in the low 40's. Sandy