Does my 1990 AC system have an oriface tube?

[Moneypit]

Does it have an oriface tube or I believe an expansion valve. I replaced the compressor and the drier and charged the system. It blows cold but short cycles, and the ac guy said that it could be because i didnt change the oriface tube or the expansion valve, he wasnt sure which one my car has, and also where is it?

 

[rangerj]

The high pressure line has an oriface tub built into it. The tube itself can be replaced but it is better to replace the line for the few extra $$. I hope you cleaned out the system and replaced the accumulator/dryer. rangerj

 

[Moneypit]

i did that but it still short cycles, could it be the pressure switch?

 

[rangerj]

Short cycling is most often caused by low pressure in the system. If the system has a proper charge of refrigerant, then yes it could be the switch, or the oriface as suggested by the A/C technition you consulted with.

The other possibility is the gap between the clutch plates on the compressor. Did you set the gap on the clutch? rangerj

 

[Moneypit]

I bought the compressor with the clutch, so no i did not abjust i just installed it and the drier. I will check the pressure switch( where is it located?) Also do you know how much freon the system should hold, we put in 3 cans!

 

[AutoSHO]

Did you happen to evacuate the system before you put the refrigerant in?

 

[Moneypit]

we put a vacume on it for 45 min.

 

[projectSHO89]

Time to hook up the manifold guages so you can see what is actually happening inside the system.

Steve

 

[SonicRiot]

Our cars have a cylcling compressor and a fixed orifice tube.

What was the vaccuum brought down to? Do you have sufficient charge? Hook up some gauges. Check out your duct temps and line pressures.

 

[rangerj]

When you say you put in three can that does not tell us much. Three cans of what, R-12 or R-134a? How many ounces of refrigerant were in each can.

If you put in R-12 in a 90 it should take no more than 36 ounces, but the best way to judge the proper amount of refrigerant is by the pressures, and temperature at the center dash vent. If you converted to R-134a the system would require no more than 85% of the amount of R-12, say 28oz to 32oz of R-134a.

The MAXIMUM amount of oil in the system should be 7.5 oz.to 7.75oz.

The low pressure switch is on top of the accumulator dryer. The gap between the clutch disks should be about .035.

the system should be vacuumed at 27hg to 30 hg for a minimum of 30 minutes. But is the system has been open for any length of time, and/or it is humid the vacuum time should be increased. Vacuuming removes moisture. Moisture in an A/C system will do the same thing to a compressor as water in the crankcase will do to an engine!

Look at your evaporator core, behind the glove box. Is it building up ice or heavy frost? Is the high pressure line getting hot, or does it stay cold?

As stated above, or below with the new format, you need to find out what is going on inside the system with a set of pressure gauges. rangerj

 

[SonicRiot]

Did you use 1 LBS. cans?

If so, you DO know that they aren't REALLY 1 LBS...

1 LBS. is 16 OZ. 1 LBS. cans of R-134a refrigerant are only 12 OZ.

So maybe you still do not have enough refrigerant. Just make sure of this.