AC Low Pressure way too high

[Norseman]

I had my AC converted from R12 to R134a today. But the LP was way too high - 150-200 psi. HP was 130-200 psi and should be OK.

We followed the procedure explained at the GNTtype.org, but the pressure-cycling switch acted a little odd. The procedure says:"You can reduce the cycling pressure by turning the screw beneath the connector on the cycling switch counter clockwise." When doing this the cycling pressure raised. Turning the screw clockwise reduced the cycling pressure. The compressor went on and off every 4 second.
Fan worked OK and I got cool air inside the car.

I have a new compressor, orifice valve and pressure cycling switch.

Could anyone help me, please, and explain why the LP is that high ??

Per B.O

 

[Nick Micale]

Are you SURE the orifice tube is not in backwards?

 

[cruzn57]

high lo side press

How much oil did you put in?
also , did you drain out the old oil?
I would have replaced the reciever /dryer, it contains alot of the old oil,
sorry to harp on the oil thing, but 134 isn't that friendly with the oil found in use with r-12
Should use ester, or Pag oil with 134, see what is available near you, , verdict is out on which is better, (like which spark plug is best)
High, lo side press ,means something is plugged, or restricted,
check it out, carefully!
good luck
cruzn57

 

[Norseman]

The orifice tube was put in as showed in GNT-type.org, with the O-ring in(as the old one).

Sorry, I forgot to mention the accumulator/dryer was also replaced.
I put 2 oz of ester oil(came with the retrofit set) in the accu/dryer, put 2 oz in the compressor and 4 oz was sucked in the system when charging the R134a.

The old system had not been in operation for years, probably cause of a blow out(the old orifice tube was packed), and contained very little oil. The old compressor was dry. The only place I found a trace of oil was in the evapurator core.

I blow each part of the system out with compressed air, before installing.

Ill take another look at the system today, looking for a restriction.

Thanks.

Per B.O

------------------
-87 GN - with some mods.

 

[Norseman]

Had the car to a garage yesterday, where they had equipment to refill A/C.
Unfortunately they where not experts handling A/C, on top of this, their automatic filling unit got broke. Fortunately it happened after emptied the system.
I took this opportunity to inspect the pipelines again. No restrictions found.
The orifice tube was not contaminatied, and was correct installed.

To fully understand how the A/C works electrically, Ive been reading the service manual for a couple of hours.
In this connection I have some questions:
1) At page 8A-201-8 fig.a there are shown two A/C switches.(A/C high pressure switch on the pipeline, and the A/C high pressure cut-out switch in the back of the compessor).
The good book says at page 8A-64-3 that the switch in the A/C line is the A/C HP cut-out switch.
Whitch one is right?
2) At page 8A-31-0 The A/C High pressure switch(two switches in one, hi closes above 300 psi and lo closes above 260 psi). This has to be the switch on the pipeline. Cant find anyone else like it anywhere?
The purpose of this switch is only to turn the coolant fan on/off. Am I right?
3) Is it the little switch(opens>430 psi, closes<200 psi, normal closed) in back of the compressor that stops the compressor when the pressure become to high?
I thought the working pressure on HP side was between 150-200psi?

Per B.O

------------------
-87 GN - with some mods.