90 Legacy L A/C

[tntkenny0927]

My legacy is once again giving me problems the A/C is acting up the compressor won't kick on only when it feels like it i did the r134a conversion i put the right amount of freon with oil been using the e z chill recharge with oil freon 12oz bottles now the gauge was on full. So everything was at its right level the a/c was on max ac setting the blower fan on high i had to drain the high pressure valve which made the compressor kick on but like i said earlier it just stop and is doing the "I'll turn on when i feel like it" deal when the compressor is on it barely blows cool air i changed all the relays and the sensor on top the silver canister that holds the freon but no luck i'm here in florida not summer yet and we're seeing 90+ days my little 1 year old is always sweating up a storm any advice please help thanks and god bless...

[Fairtax4me]

The gauges on the little refill bottles are inaccurate at best. The whole system should only hold about 18-20 oz iirc. There should be a label showing how much the system holds, usually in Kg, but that can easily be converted to oz with google.

 

The system pressure may still be too high or the pressure switch may be bad.

Find someone with a manifold gauge set and hook it up to see the actual pressure in the system.

[Legacy777]

Check out my r134a conversion thread on the legacycentral bbs.

 

http://bbs.legacycentral.org/viewtopic.php?f=11&t=1083

 

I'm not a huge fan of those "easy & quick" conversion kits.  They just don't work well.  A properly converted r134a setup works very well.  I'm in Houston and have similar humid weather as Florida.  The AC in my 90 Legacy works better than my 97 Impreza.

[Rooster2]

If you charged with only one 12 oz can of 134A refrigerant, then I don't think you have enough refrigerant in the system.

 

It is my experience that when a system is low on refrigerant, it behaves exactly like what you are experiencing.............the compressor only casually comes on lazily,  and blows just slightly cool air, then shuts off. Add another can (smaller size can) of 134a, and see what happens.

[capn_r]

Was the system evacuated prior to the charging?  If you had to "drain the high pressure valve" to to get the compressor to come on I would guess the trinary switch was open due to excessive pressure. ( I may be mistaken that the EJ's have trinarys)  The probable combination of non-condensable gases and the refrigerant creates very high pressures. (Dalton's Law)

[tntkenny0927]

the old r12 system was completely evacuated properly and the conversion was just the regular autozone type kit just the 2 fittings i originally had about 2 cans 12oz and close to a 16oz of course with the gauge kit it came with i recently had my tires changed and had the technician check the ac real quick he had the manifold gauge set with the 3 gauges and valves said the pressure was high and the freon was low so i drained the high valve dry then put a 12oz can same ez chill stuff to proper readings but ran into the compressor being lazy same issue when bypassed to constant 12v power compressor ran fine and blew barely cool...

[Legacy777]

Capn_r, yes the Legacy has a trinary switch on the receiver drier.

 

 

kenny,

 

When you say the r12 was completely evacuated, did you have a shop do it?  If so, what exactly did they do?  The old mineral oil isn't compatible with r134a.  Was the old oil removed and new oil put in?

[tntkenny0927]

i believe all that was done was the gas and freon evacuation this weekend i'm gonna tear it apart and drain it all like the write up by josh legacy 777 is posted i will replace the dryer receiver and the blower filter i will drain the oil from the compressor also the gas and freon from the compressor and lines a complete drain and buy the gas oil and freon seperately and do the job right i have no other choice need to keep my baby cool in this hot state will keep u guys posted thanks legacy 777 for that write up i do appreciate it guys.

[presslab]

Yeah, in a place like Florida you'll want to fix it for the long term!

 

I recommend one of the hydrocarbon refrigerants like ES-12a; they work at pressures more similar to R12.  R134a systems have different TXV and switches because the pressures are different.  The R134a condenser is larger because the specific volume is larger.  Rather than change all that, or have 20% reduced cooling, it's easier to use one of the alternative refrigerants.

 

If you flush it all out and start clean I'd use double-end-capped PAG oil; POE oil doesn't lubricate as well, and can coke (break down/burn) if it gets too hot.

 

You might consider replacing the TXV as well, at the least remove it and clean it out really well.  This may be the source of your problems right now.

[capn_r]

I think maybe refrigerant recovery is being confused with evacuation. (Pulling the system into a vacuum)

[Legacy777]

I have not used the R12 alternatives, so i can't comment on them, but I can tell you from first hand experience that there is little to no noticable reduction in cooling capacity by using roughly 80% r134a of the original R12 capacity.  As mentioned, the converted system in my Legacy cools better than the original r134a system in my Impreza.

 

I agree with capn_r, there may be some confusion on evacuation and pulling a vacuum on the system. 

 

Kenny, once you've cleaned the system, changed the oil, and have the system sealed back up, you need to pull a deep vacuum on the system to boil off any moisture that may be left in there.  I typically will pull a vacuum for 45-60 minutes, close the system, make sure there are no leaks and then charge the system.  If you do not have a vacuum pump and gauges, I'd suggest doing all the work up until that point and then take it to a shop to pull a vacuum and charge the system.  Based on my own personal experience I'd double check and confirm with them the amount of time they plan to pull a vacuum on the system, and inform them of the amount of refrigerant you want the system charged to.

[presslab]

I have not used the R12 alternatives, so i can't comment on them, but I can tell you from first hand experience that there is little to no noticable reduction in cooling capacity by using roughly 80% r134a of the original R12 capacity.  As mentioned, the converted system in my Legacy cools better than the original r134a system in my Impreza.

I'm glad it works well for you, and filling it will less refrigerant doesn't sound like a bad idea in this case. R134a is certainly an option for those that are afraid of hydrocarbon refrigerants. R134a is a "super greenhouse gas" and can react corrosively with moisture.

 

Filling it with a different volume of refrigerant does not change the fundamental vapor pressure. You can see the differences here:

http://www.refrigerantguy.com/PTC.htm

 

The Legacy has a larger cooling capacity (BTU/hr) system than the Impreza.

[Legacy777]

Thanks for sharing the chart.

 

I agree that the 12a is a closer match to the original R12 refrigerent.   But, it appears that there is only a single digit difference between the R12 & R134a vapor pressure until around 108 deg F, and maxes out at 18 psi difference at 129 deg F.  Is that a huge difference and enough to cause poor operation of the AC system.....I don't know.

[presslab]

Yeah, that's why you hear people say that the high side pressures are higher with R134a. Because the R134a needs a higher pressure (at the same temperature) to become liquid, that means it's harder work for the condenser and/or compressor. High side pressure isn't on the chart, but you can imagine the temperature difference at the typical ~250 PSI. If you reduce the pressure in the system (by charging with 80% volume for example) then the low side suffers because now the pressures are too low there.

 

The TXV in our cars can compensate a lot for pressure imbalance, and that makes it more tolerant to R134a retrofit. Other cars (typically domestics) use an orifice tube which doesn't work so well when pressures are off.

[Legacy777]

That's good to know our cars respond better to the retrofit.

 

It's been a while since I've put the gauges on my car to see where the pressures sit.  I should probably do that before it gets too aweful hot here in Houston.