Inline Filter--High Side or Low Side?

[Vardaman]

I replaced the compressor and condenser on my Suzuki, after a previous owner let them sit open while driving the car. I flushed the system before creating vacuum and refilling, but the replacement compressor failed--My guess would be that it's because I bought a Chinese POS compressor with crappy seals that gave out. No catastrophic failure, but I'm open to the idea that maybe there was residual contamination in the system that compromised the seals, and I don't think a filter would hurt anything--especially since it's relatively easy to install now that the system is empty.

I'm now installing a used stock compressor, but I want to make sure there's no crap circulating in the system. I'd like to install an inline filter. I see two types--barb-type for the low side (generally pretty inexpensive) and compression fitting for the hard lines on the high side (generally over $50.) My inclination is to think that if most filters I see are high side, that's the better way to go. Still, I don't want to piss away extra money on something that doesn't work better, or has a higher chance of failure.

Is there a reason that either a high side or low side filter is better?

[JohnHere]

A few questions to start, if I might:

How did you flush the system and with what? Dry out all the components thoroughly after flushing? How did you evacuate it and for how long? How did you charge it, by exact weight-of-charge or by "guestimation?" Did you use pure refrigerant-- that is, no sealer or other additives? Did you put any oil in the system? If so, what type of oil? Did you replace the receiver/dryer?

The parallel-flow condenser (on the high side) serves as a large system filter. In my opinion, if you're starting with a clean and "dry" system, along with a new PF condenser, there's no real need for an auxiliary filter.

[tbirdtbird]

Your PF condenser is likely clogged with debris, due to the comp failure, and they cannot be flushed. Replacement is the only option.

We see this problem somewhat often....compressor grenades, sending shrapnel to the condenser. Owner then replaces only the comp, and the debris in the system works its way back to the new comp, and then it fails as well.
If comp is replaced, cond also needs replaced

[Vardaman]

To begin with, there was never a compressor failure. The original compressor was damaged when a bolt in the engine compartment sheared and tore off the low-side port. After this happened, the previous owner left the parts hanging for quite a while, so it's possible that dirt got in. The compressor was never activated after the damage occurred.

I flushed the lines with A/C Pro Flush & clean, then blew the lines out with compressed air, after which I left all the lines open for two days so the solvent could evaporate. I then installed a new condenser, drier, and compressor. There is no orifice tube to replace in the Suzuki--just an expansion valve/block. I used manifold gauges and an electric vacuum pump to evacuate the system (after adding the correct amount of PAG oil) ensured that there was still vacuum after 24 hours, then filled the system with 134A, using the manifold gauges to ensure I was adding the right amount.

Six months after installation, the pulley on the compressor snapped and it was clearly a bad casting that caused this. Then a year after installation, the R134A began to leak out the front seal of the compressor. Leading me to the conclusion that Chinese-made compressors are garbage.

I still feel more comfortable having a filter in the system, so my question remains. Low side, or high side?

[JohnHere]

OP, if you post the year and model of your Suzuki, I'll look up the refrigerant and oil specs when I return home from vacation later this week.

[JohnHere]

"If" I was inclined to install an aftermarket filter, I would do so on the high side between the compressor and condenser to catch any debris that the compressor might shed.

Be aware that a salvage yard compressor (as well as rebuilts) are hit or miss as to whether they will last or even work. A new unit with a warranty is always preferred.

Also, a stock MVAC system CANNOT be accurately charged by pressures. The refrigerant must be weighed-in precisely, especially a system like yours that holds a very small amount--perhaps one pound or thereabouts--in which the margin of error is very small. Only one or two ounces "off" will negatively affect cooling performance and might oil-starve the compressor.

[Vardaman]

Sounds good. The workshop manual says 80cc of PAG 46.

[Vardaman]

So how is a DIY mechanic able to add by weight? Is it as simple as weighing the cans before and after? Or are you suggesting that this simply isn't a DIY kind of job?

[tbirdtbird]

Well, charging is not as easy as it once was. In the R12 days all you had to do was clear the sight glass. Those days are long gone.
There are dedicated refrigerant scales, and there have been posters here who have managed to use a postal scale. The weigh in method is truly the best way to go as John says. And be aware that you can seldom get all the refrigerant out of those small 12oz cans, so weighing before and after is a good idea.
Most of us here on the board have a refrigerant scale and fill from a 30 lb jug

[JohnHere]

The commenter immediately above, tbirdtbird, has it exactly right.

You can charge it yourself, but you need to have both the knowledge and proper equipment. As said, a postal scale will work, but it should be a good one, very accurate, and be able to count down from the tare weight. That is, you would put the small can with the yellow hose attached onto the scale, and then press the "tare" button, which will zero-out the display. Then begin charging and stop when you reach the exact weight-of-charge (this will be a negative number on the display).

Incidentally, what year, model, and engine size is your Suzuki?