Automotive Air Conditioning Information Forum (Archives)

efxengr on Sat July 21, 2012 4:13 PM

Year: 2001
Make: Hyundai
Model: Elantra
Engine Size: 2.4L
Refrigerant Type: 134a
Ambient Temp: 88
Pressure Low: 30
Pressure High: 195
Country of Origin: Korea, Dem. People's Rep of

A/c hasnt worked in a year but when checked had a residual low/high pressure of 30psi so doubtful it leaked down. Car driven regularly, has 190,000 miles. Before settling on the pressures above I got the following:

Idle:
Amb 88F
Low 35 psi
High 215 psi
Vent temp 72F

One guide I found says Low should be 35, high should be 180-190.

1700 rpm:
Amb 88F
low 18 psi
High 230 psi
Vent temp 72F

Engine off low/high = 125/150

I bled off some refrig and got:

idle:
Amb 88
Low 30psi
High 195
Vent temp 72F
Engine off low/high 110/150

When reved suction drops to about 20 quick and high goes to about 225.

Note, on this car the low side connection is between the txv block and the compressor inlet so its reading true suction pressure. Also, when adding 134a I had to very carefully throttle the low side valve...if not the suction pressure would rapidly jump to 60-75 psi. It seems like the TXV is sticking...not allowing cooling and starving the compressor when reved up. Also, would seem that if the valve was full open the suction pressure wouldnt react so quickly when filling.

When car is off the pressures arent balanced so either the valve is stuck or the condenser is clogged. Doesnt the compressor have a check feature such that the closed (stuck) TXV would isolate the suction line on the compressor from the rest of the system?

Another question...has anyone tried changing the dessicant bag in the combo condenser/drier on these cars? Is it better to just replace the condenser.

Thanks for any help.

Edited: Sat July 21, 2012 at 4:21 PM by efxengr

mk378 on Sat July 21, 2012 6:00 PM

30 psi static means the refrigerant was about 95% gone, 5% remaining. How much did you add?

Do the condenser fans work?

This looks like it might be a variable compressor system, those really need to be charged by weight.

efxengr on Sat July 21, 2012 6:51 PM

Condenser/radiator fan(s) were working...one stayed on the whole time when the a/c was on. Compressor came on and stayed on. Added less than 14 oz, probably 8-10 but didnt weigh, only approximating by what is left in can. Used operating pressures at idle and 1700 rpm as a guide to filling.

As a followup I noticed that the txv has a plastic cap on top. I removed it to see the end of the valve shaft/rod. Should that move in and out? it never moved when testing.

Edited: Sat July 21, 2012 at 6:53 PM by efxengr