A/c sucks bad expansion valve?

[Kevinl]

My car has been converted to 134a today was the first decently hot day of the year and it was barely adequate once it gets hotter forget about it

I took a temp at the vent and it was blowing 74 degrees at idle hooked up gauges the low side reads about 45 at idle and when I rev it up the suction pressure drops way low down to 10-15 psi
I'm sure the car still has the r12 expansion valve since I have a receipt when the previous owner got it fixed and there is no mention of replacement

[bmwstudent]

Need head pressure, suction pressure, ambient air temp, to make an educated guess. I'm not sure what the low pressure switch kicks out at but ten psi is the low end of where it should be while running. I would hook up the manifold set and run it to watch the pressures.

[cabriodster87]

You may just need a little refrigerant added, i topped up my system yesterday and pressure/ temp is good as it gets.

[Kevinl]

It is 35 psi low 185 high at idle with 80 degree outdoor temps when revved the suction pressure drops down to about 11 and then slowly rises to about 15 psi

[glucklich21]

Read the temps and pressure link in my DIY http://www.r3vlimited.com/board/showthread.php?t=246743

[Kevinl]

I ve looked over your DIY quite a bit. I find the BMW document to be confusing are these readings taken at idle or cruising

I find it hard to believe the head pressure would only be 85 Under these conditions

It will blow down to about 47-48 while going highway speeds when it is under 80 degrees outside when it is 95-100 it will only blowto about 65 degrees on the highway and 75 at idle

Aux fan has been replaced by previous owner with a aftermarket one the resistor is bypassed as well

[glucklich21]

Replace the expansion valve. If that doesn't solve it, I wouldn't be surprised if your compressor is past its prime. My idle and at speed temps weren't far from each other +/- 5 degrees with a new compressor. The pressure readings on the BMW doc is at idle.

[Kevinl]

The compressor was replaced two years ago I think it's fine I have a receipt for all the repairs that were done but I do not see an expansion valve on there

So thats what I am leaning toward
I wish it was still R12 but I don't think I want to go to the trouble to convert it back

I am EPA 608 & 609 certified so I can buy r12 but flushing all the oil out of the system is something I don't want to bother with

[Bmjpv]

a/c

You should look into Freeze 12 , works much closer to r12 than r134 ever thought about. Joe

[bmwstudent]

What does the high side go to while at high idle (1500-2000 rpm)? If the low side is going down below ten psi and the high side won't develop more than 200 psi you might try a little more refrigerant. Before you start adding refrigerant though I would look over the system for basics like a restriction at the drier, check to see if it's icing up while the system is running. It should NOT be, if it is then it is bad. The suction line from the evaporator to the compressor SHOULD be sweating ice cold water off of it, but it really should not be developing icing frost on it, a little is ok but you don't want it to freeze the entire length of line. The condenser should be hot to the touch where the line enters it and warm where it leaves it and goes to the drier, the drier should be warm. You said your compressor was putting out 180 psi at idle, I doubt it's bad. I know when we were converting trucks over in the late 90's early 2000's we would often change the expansion valve and the compressor cycling switch or the high pressure switch (fan switch), because the operating pressures for 134 are much higher and the r12 switches simply would not let the system get up to a high enough pressure to actually change state and cool properly. Most fan switches for todays tractor trailers kick the fan in around 350 psi and then kick out around 250. The only time the compressor is turned off is if the cold switch in the evaporator starts to get too cold and freezes up( which actually means the system is working properly). But that is a tractor trailer system. I'm not sure but I believe that these cars use a compressor cycling switch instead, which means the compressor is cycled anytime the head pressure gets too high, and whenever the cold switch recognizes that the evap is down to temp and no longer needs to be cooled. At any rate the compressor should be expected to cycle on and off at some point but not constantly. I COULD BE WRONG on the compressor cycling switch, I have not been into the a/c on an e30 yet I'm just giving generic a/c info that can be applied to any a/c system.

[Kevinl]

Yeah after reading more I think it may be undercharged I will try refilling it by weight before tearing the system apart

[bmwstudent]

Just hook up the gauges and add 1/10th of a lb until it starts to act properly, when your retrofitting a system there isn't always an exact known perfect quantity. Unless someone has done a few and knows what has worked well in the past for them. Start with the recommended amount for r12 then just give it little more until it starts working. (cold suction line, hot discharge, cold air, etc. Remember more is not always better, if the system gets too full it won't work properly either.

[bmwstudent]

If you don't have a scale to dispense by weight, just give it little burps of refrigerant through the low side line. Crack open the valve and let a little go through at a time, then close it off and watch the gauges. You may want to put a decent fan directly in front of the condenser(radiator) to mimic driving at highway speeds, because sometimes the clutch fan will not pull enough air to cause the change of state(of the refrigerant) in the condenser.

[Kevinl]

I took the car to my uncles shop and had it evacuated& recharged it works ok now

my e36 never had great ac either

My suburbans a/c will freeze you out but the condenser is twice the size of the e30's

[Kevinl]

I drove it this morning and it about froze me out.
When I picked it up from the shop it was sitting in the sun all day and was 105 degrees out side