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cebudave
05-01-2017, 09:04 AM
I have a vehicle which the a/c (134a) is not going below 70f. Outside temp 85f. Low side pressure 30 to 35 psi high side 185 psi. I believe thermostatic expansion valve is work (its new)because I see the pressure will hold at 30 then move to 35 psi then a few minutes latter it will return to 30, high side changes accordingly with low side.

The discharge of the expansion valve is a little cold to the touch.

Is the expansion valve out of adjustment? if so would I increase pressure on the spring (turning counterclockwise) or decrease the pressure (turning clockwise)?

to adjust it I have to remove it. Right now the system is void of 134a.

The Viking
05-01-2017, 04:56 PM
high side changes accordingly with low side.

Most likely you got an issue with the amount of refrigerant in your system. The way forward is to ensure you get the system to a deep, standing, vacuum (<3Torr) and then recharge the system with virgin 134a, weighing it in according to the manufacturer's specification.

:cool:

chemi-cool
05-01-2017, 06:27 PM
And make sure all heating pipes are closed.

charlie patt
05-01-2017, 07:46 PM
What is vehicle.and age

cebudave
06-01-2017, 12:35 AM
What is vehicle.and age

its a 1992 Suzuki every van, the pump, drier, and expansion valve are new. flushed the whole system also.

I was thinking the expansion valve is out of adjustment

mikeref
06-01-2017, 09:12 AM
No mention of Evaporator cleaning or replacement. A New Factory set vehicle expansion Valve rarely need any tinkering.
Over in OZ, a 20+ year old Evap is past it's use by date.
Suction pressures mean bugger-all unless a specific Engine RPM is included.
Loss of Gas is one possibility. :)

hyperion
06-01-2017, 10:54 AM
Check that the evaporator fan motor is running at the correct speed and that the fan blade is not dirty causing a reduced airflow.

charlie patt
07-01-2017, 08:34 PM
At that age first thing is
1, is it on the correct gas on 1992 could be on 12
Also lot more info please firstly is it fixed speed or fan speed controll condensor fan
Has the system been hp tested overnight to prove system held pressure vacing and holding a vac not good enough
If system been flushed what amount of oil been installed
and is it single or twin evaporator when you say van ie commercial or people carrier sorry but in devon van to us is a commercial vechicles
On system like this you have to start from the beginning otherwise u end up going around in circles my issue is slightly high low side and at that ambient not enough head ta charlie

lzenglish
08-01-2017, 12:00 AM
And make sure all heating pipes are closed.


I agree! If the unit is charged to specs., check your heating water system for unwanted heat leakage air mixing. Your vehicle may or may not have a hot water hose shutoff valve, but may have a supply air mixing door instead.

cebudave
13-01-2017, 04:28 AM
Ok two years ago I changed the pump from r12 to a r134a one, r12 pump no longer available. After which the system was flushed with denatured alcohol, dryer changed, expansion valve, and recharged with r134a.

Right now its 40 psi and 250 psi, temp 70F, this is at idle 900 rpms. All fans ae working properly.

Question is if I screw the hex screw in it should increase the flow into the evaporator? thus lowering the superheat.


At that age first thing is
1, is it on the correct gas on 1992 could be on 12
Also lot more info please firstly is it fixed speed or fan speed controll condensor fan
Has the system been hp tested overnight to prove system held pressure vacing and holding a vac not good enough
If system been flushed what amount of oil been installed
and is it single or twin evaporator when you say van ie commercial or people carrier sorry but in devon van to us is a commercial vechicles
On system like this you have to start from the beginning otherwise u end up going around in circles my issue is slightly high low side and at that ambient not enough head ta charlie

charlie patt
13-01-2017, 09:27 PM
On provision u have the correct level of refrigerant ,,,,on that age in uk we would have a sight glass and 900 rpm your suction pressure is to high if needle on gauges not flickering I would suggest oil charge incorrect or bad pumping comp this is on condition gas level correct if you bring you revs up to 1250 partly cover condensor with cloth sea what suction is if head rises slightly suction stays same comp poor or bad oil level 12 and 134 valve ni on identical but at high ambient they suffer screwing the valve will do little but they do have a sive before them if the valve body icing on comp side this indicates this but this normally covers low suction also is there any sweating on suction line I pressume gas level been checked recently????

cebudave
25-01-2017, 05:50 AM
Ok, I just took the following pressures and temps Low 40 psi, charts says that's 45*, outlet pipe to evap 80*, High 200 psi, chart temp 130*, inlet pipe to expansion valve 102*

Outside temp 85*. vent temp 58*. engine rpm 900

superheat P/T 45* minis 80* = 35*
subcool P/T 130* minis 102* =28*

Sight glass on drier looks foamy

Now the whole system was flushed, and blown out with air. Vacuumed system to 28 hg held over night

Replaced drier, expansion valve, and condenser fan with a higher cfm (fixed speed)

So do I need to open the expansion valve a turn out to allow more flow into the evaporator? Or is there some other thing I am missing. Any help would be appreciated.

charlie patt
25-01-2017, 08:16 PM
As previous your suction is to high your head to low if you have a higher speed fan at 900 rpm engine revs your short 50 psi head and suction 10 psi to high sight glass should be clear at this ambient you should be running 250 min with high speed fan most systems will hold a vac holding pressure on cars is a different thing before playing with tev u really need to check gas level your sight glass is active because it's short or something in system that should not be or oil the biggest problem is most of the above work is just worrying who flushes then blows out with air then replaces tev, also fitting higher speed fixed fan on a car is silly most have variable speeds to allow air flow when driving only ones that don't is subcooled units which this is to old I think you just need to start from basics a basic car ac is simple but if you alter parameters and you don't no what you are doing you just make it worse the biggest problem you may well get it correct on idle then you take it up the road and due to engine speed and airflow vechicles ac don't work

cebudave
26-01-2017, 02:17 AM
As previous your suction is to high your head to low if you have a higher speed fan at 900 rpm engine revs your short 50 psi head and suction 10 psi to high sight glass should be clear at this ambient you should be running 250 min with high speed fan most systems will hold a vac holding pressure on cars is a different thing before playing with tev u really need to check gas level your sight glass is active because it's short or something in system that should not be or oil the biggest problem is most of the above work is just worrying who flushes then blows out with air then replaces tev, also fitting higher speed fixed fan on a car is silly most have variable speeds to allow air flow when driving only ones that don't is subcooled units which this is to old I think you just need to start from basics a basic car ac is simple but if you alter parameters and you don't no what you are doing you just make it worse the biggest problem you may well get it correct on idle then you take it up the road and due to engine speed and airflow vechicles ac don't work

Ok, so what should the low psi be at idle? The drier, where the sight glass is, is before the TEV on the high psi side. From my understanding the r134a at that point is to be 75% liquid and 25% gas, or am I wrong regarding this.

Could you give me the following info, ball park figures would be fine.

Low side PSI -
outlet temp evaporator -
High side PSI -
Inlet temp to TEV -

This a Suzuki super carry van. the condenser is underneath the vehicle, not in front of the radiator. The stock fan was a single speed fan. It was pulling too many amps, that's why I replaced it and the radiator fan.

cadwaladr
26-01-2017, 04:45 AM
I would take the evaporator out the condensor out and remove the oil from them of course refit them fit a 134a valve another new drier drain the compressor oil and refill it with the oil for 134a pressure test vacuum the system and recharge with 134a to the manufacturers specification,after all that it should work and the aircon repair will be worth more than the vehicle!!!