Quick A/C question on pressure

[MY90GT]

Did a total r12 to r134 conversion several months back.
Just getting time to fool with it again. Been to hot.
It's 74 degrees out with low humidity.
Engine idling at 1500 rpm
AC on MAX, fan on high.
Suction side pressure 65
Discharge side 205.
Suction side looks a little high. Is that a sign of too much
freon or not enough

Thanks,

 

[jrichker]

The suction pressure is high. Usually overcharging results in a higher discharge pressure than what you indicate.

 

[MY90GT]

So, does low pressure, high suction indicate a low charge.

 

[jrichker]

The only time I have seen the suction go high when the compressor was running was when charging the system. I really don't have a good answer for you.

Try emailing PuterAmI, since he is the other resident A/C guy.

 

[MY90GT]

Thanks,

 

[PuterAmI]

Did a total r12 to r134 conversion several months back.

Suction side pressure 65
Discharge side 205.

Could you define "total conversion"? It appears that you have a restriction. Most common is the orifice. So, I am wondering if you changed out the liquid line with fixed orifice.

 

[MY90GT]

Total, everything. The original replacement compressor went out about a month before the warrenty went out. Clutch pack. Installed a new one.
Added some additional oil, vaccumed, charged with 2 cans of R134.
Went back about a month ago, when the temp. outside started going up.
That's when I noticed the high suction, low discharge temp. Could it have to much oil? I'm about ready to "recover" the system, vacuum and recharge.

 

[89 Saleen#455]

Another Vote for a clogged or partially obstructed O-tube.

Did you flush the entire system (with the exception of the compressor, accumulator, and new O-tube) with mineral spirits or brake cleaning sovent before pulling vacuum?

 

[PuterAmI]

Another Vote for a clogged or partially obstructed O-tube.

Did you flush the entire system (with the exception of the compressor, accumulator, and new O-tube) with mineral spirits or brake cleaning sovent before pulling vacuum?

My thought exactly when I read the above post. When the compressor "went out", it threw particles into the system. If the system was not flushed, they gather and clog the orifice which is the smallest point of the system.

Yes, if you added oil without knowing how much is in there, you have too much. Another reason I hate death kits.

If it was me, I would go ahead and recover the system and flush it. You'll also need another liquid line with orifice.

 

[MY90GT]

When the new compressor went out, the compressor was fine, it was
the clutch pack that went out. Since the compressor was still under warrenty, they gave me a whole new compressor, insteady of just the
clutch assembly. I swapped out the compressors, added about 6oz of
additional oil, vacuumed, added 2 cans of Freon.
I need to be clear, that when I did the conversion, I did not reuse ANY of the old parts. Everything new went in, lines, orifice, compressor, evaporator, condensor, everything, right down to the new R134 cutout switch.

 

[89 Saleen#455]

If it was me, I would go ahead and recover the system and flush it. You'll also need another liquid line with orifice.

Puter's response is right on the money!

Recover the system. Pull the accumulator and plug both ends to prevent moisture from absorbing. Pull the liquid line and replace. Flush the remaining components with mineral spirits (with the exception of the compressor). Drain all the oil from the compressor. Reinstall all components adding the following PAG oil amounts: 4oz. in compressor, 2oz. in the condenser, and 2oz into the evaporator. Total oil charge should be 8oz. Pull vacuum for a min. of 1 hour and charge.

 

[MY90GT]

Put a fork in me I'm Done......

OK, went with your advice, and here's what I've got.
91 degrees outside air
Low humidity
Air on Max, doors open
Fan on high.
Suction 26
Discharge 245
Engine idling at 800 rpm
I have a 33 degree drop between air entering the HVAC unit
and discharging at the vents.
92 in, 59 out.

Does that sound about right??????
If not the car is going up for SALE !!!!!

 

[jrichker]

OK, went with your advice, and here's what I've got.
91 degrees outside air
Low humidity
Air on Max, doors open
Fan on high.
Suction 26
Discharge 245
Engine idling at 800 rpm
I have a 33 degree drop between air entering the HVAC unit
and discharging at the vents.
92 in, 59 out.

Does that sound about right??????
If not the car is going up for SALE !!!!!

Sounds good to me. That's about what mine is running lately.

 

[MY90GT]

Thanks for your help......

 

[PuterAmI]

I get 42 on a 93 ambient day.

Take a water hose and sprayer and spray your condenser. If the high pressure falls pretty much, I am thinking you are still undercharged by ~2-4 ounces. Also check the condition of your fan. It may not be working as it should since this reading is at idle. Also let me know what they are at 1800RPM.