AC Question for Glacier

[85Dave]

The AC isn't cooling very well in my 92. I converted it a couple of years ago when I replaced the compressor. I flushed the condenser and evaporator until I got clear solvent out. Replaced lines, accumulator, orifice tube, all o-rings, and compressor. At the time, it was cool, but not cold. Now, it just barely cools. Today I checked the temps and pressures.

Begining
Outside temp - 94 F
Vent temp - 66 F
High side pressure - 255 psi
Low side pressure - 27 psi
rpms - 1500

I slowly added 134a until the temp just started to rise.

Ending
Vent temp - 55 F
High side pressure - 290 psi
Low side pressure - 35 psi

The temp briefly went to 54.9, but stabilized at 55.4 F. That's when I quit adding freon.

Any ideas on why the temps don't get colder?

 

[hermitrl]

Just curious---how often does your compressor cycle? having similar problems.

 

[85Dave]

It doesn't. The compressor was compressin' the whole time. Maybe an hour or so. I put a box fan in front of the radiator the whole time.

 

[Glacier991]

When you are just running vent air, is it the same as outside air, or is it a little warmer? My 92 bleeds a little warm air in (even with the heater control "off"... I haven't been ambitious enough to check out why, but that is one possibility. Another might be the orifice tube. They come in a flavor for 134 systems.... On the rebuild - How long did you evacuate it and to what level? You could have air in the system too. Other than those ideas? Tell truth I really am not certain.

 

[hermitrl]

Well I filled mine myself--and think I overfilled it as the compressor would not cycle. I actually had freon jetting out the relief valve when reving the engine. I released some from the high side until the compressor would be able to pump the coolant pressure to 25 pounds or so where it would finally click off. It is much cooler now but still not quite there yet. waiting till payday to get it properly filled. perhaps yours is overfilled and the compressor can't get the low side down enough to trigger it off? Mine would not cycle off until the low hit 25 on a cheap guage.

 

[monkeydude3]

To me those high side readings seem too high. They should usually be around 150 psi or so, give or take, when running. When off, the high and low side should be very close and in psi, very close to the degrees in F that the air temp nearby is.

It does seem like the orifice tube. That is like a pinhole, and basically turns the compressed R 134A to a mist type state, and at that point when it goes from very high pressure to low it cools. If that gets even a little restricted you will lose cooling. Look into that, because your high side seems a bit high. Low side seems to be reading normal.

George

 

[Longjohn119]

You probably had a metering device (orifice) problem (your 1st reading had an abnormally high head pressure) This is a sign the liquid side is 'backing up', in other words it isn't going through the orifice fast enough, starving the evaporator coil, hence the inadequate cooling, and backing up liquid line, hence the high head pressure

Now you probably have an orifice AND an overcharge problem (If it's not overcharged now then you have a leak to fix ) ... you'll probably have to recover, change the orifice and then weigh in a new charge (best way to get it right)

 

[Glacier991]

His high side is not necessarily too high for 134. It is entirely within "possible" range. A really high high side for 134 is over 300-325. THAT would be because of a condensor not doing it's job (or real high ambient temps or inadequate airflow) or other problems.... he said he had a fan on it...at 94 degrees! So his pressures are "ok" in my book. At least didn't excite me overly... if you really are worried try it again and squirt water on the condensor every few mins.....WITH the fan.

134 runs HIGH head pressures in converted systems (cuz the condensor is too small)....s'why many conversion kits come with a hi pressure release to be installed as part of the conversion.

and with all due respect.... 150 psi high side on 134 at 94 degrees is not a normal reading. You should expect into the 200's

And if I had it, I'd recover, replace the orifice tube, properly evacuate and recharge.

 

[85Dave]

When I charged the system after the retrofit, the pump I was using could only pull about 26 or 27". So I know there is some air in the system. I've seen some used vacuum pumps on ebay. Various brands. Do you have an opinion on used pumps?

Also, which orifice tube do I need for the retrofit? What about variable orifice tubes?