DIY A/C repair questions.

[zavikan]

Ok 02 hyundai sonata GLS


Compressor died, honestly there were other problems. Some blockage someplace. a/c worked sporaticly (super cold sometimes, no a/c at all on others). I think the previous owner kept dumping quick fix crap into the system. Then the compressor clutch fried half engaged.


So. First couple steps...

Remove compressor.
Remove orifice tube
Remove dryer
Remove condenser (I hear THIS is were the gunk builds up, not the evaperator)

Now what?

Do I need to buy a special flush for the lines or would compressed air work? Do I even need compressed air? Should I compress air the lines thru the evap core?

Once I get replacement parts for the 4 parts above, do I just install it or do I need to prime the compressor w/ oil?

The belt isnt even on the A/C right now, so can I kind of replace it piece by piece (im to busy to do it all in one sitting) or will that recontaminate? can I prevent recontamination?


@$*(^@#*$&

James

[gl1674]

James,

The first question is where the blockage came from. Otherwise your new compressor will repeat the fate of the original one.
It could have been water in the system, it could have been defective evap temperature sensor (hint - your "super cold" remark might be the lead to the initial compressor failure). Evaporator should not go beyond freezing point. If it freezes, it may cause over-pressure in the system with the sad consequences.

The next question is whether you have metal debris in the system. Disassemble old compressor and look at the pistons, valves. If these are not broken, you can get away without the flush. If these are broken, then liquid flush is a good way to ensure there is no metal left in the pipes. Metal shavings are not compressible, new compressor will not like them.

Yes, use compressor air to blow out everything from the lines. You don't know how much is left there, so one way to put the right amount of oil is to get the old one out.

New compressor should come pre-filled with some amount of oil. It might be enough for the full system, but do check the compressor labels and factory manual. The compressor is lubricated by a mix of oil and R134 circulating around, you need the right mix for compressor to live long and for a/c to work well.

While you are working on it - keep all system closed off the air, don't keep the pipes open - you don't want any atmospheric moisture inside.

Before you charge the new system you are supposed to evacuate air from it with a vacuum pump for 30+ minutes.
It serves two goals:
- Removes any water vapor or liquid water from inside the system (water tends to freeze, block pipes and break everything, not even mentioning corrosion)
- Improves A/C efficiency (compressing air in the system wastes energy, but does not do any effective cooling)

You'll need a vacuum pump for it. There are a couple of choices:
1. Real motor-driven pump, works from 120v ac
2. Compressed air-driven bernoulli effect pumps - these need a decent supply of compressed air and don't do as deep vacuum - read specs before getting one. I have one of these and using it is not fun - lots of noise, but got the job done.

[zavikan]

Ok, well this is what I've done so far...


Removed everything from the car but the evaporator itself. Nothing seemed to have shavings in it.


Next step for me:

A/C Flush can from Autozone on the hoses and evaporator
Compressed Air on hoses and evaporator to dry out/blow out the flush
install brand new accumulator drier/compressor/condenser/expansion valve
Hook up all the hoses w/ new o-rings(do I need to put a bit of oil on them?

Now I have an empty -clean- system.

From what your saying, it sounds like the next steps for me are:

reinstall belt to the compressor
have the system vacuum pumped
Check instructions that came with the compressor for oil + r134a ammounts
turn on A/C and start the refill of r134a + oil


Any way to find out how much oil to add? do I need to 'prime' the system by dumping oil in a line before it gets vacuumed?

Thanks for the info so far.

James

[gl1674]

Whether to put a bit of oil on o-rings - it does not hurt and makes assembly easier/safer for o-rings. But if it is already assembled I would not bother redoing it.

The last re-man compressor I installed came with a full charge of oil.
Actually it had been charged with mineral oil for R12 and had another small can of PAG for R134. I had to drain the oil from compressor and refill it with PAG prior to bolting it on.

How much - no idea. SVX manual calls for 150 ml of oil for R12 based system;
I don't think R134 is much different (oil type is different, amount not so) but it can vary between car models (it depends on compressor design and size of
evaporator/condenser).

Oil comes first, before R134 (compressor has to be lubricated any time it rotates). There is a catch - oil is not compressible, if you pour all oil into suction port and then try to crank the compressor, you might get a hydrostatic lock and it might break. The instructions called for manually spinning the compressor 10+ times before installing the belt or turning it on.

For the same reason R134 should not be dumped in the liquid form at suction port - you get hydrostatic lock as well.

SVX manual calls for 29.7 inHg vacuum for 15 minutes prior to charging
and another 5 minute wait (testing for leaks or residual water evaporation) with evacuated system.

Are you going to charge with vapor (can valve up) or with liquid (can valve down)? Liquid can go only on high pressure line and only with engine turned off (otherwise the can will blow).

SVX manual calls for liquid charge first and then completing with vapor (not all liquid will go by itself and vapor suction is sloooow)