Blazer HT6 Questions

Hey guys, Im hoping somebody can confirm some a/c questions for me. Im still learning on a/c so hopefully they dont seem too basic.

Have a 97 4.3 blazer with a HT6 compressor and no working a/c. The body seals on the compressor leaked out the dye all over and I can find no other leaks in the system. Note that the compressor still works and did not fail, thus I dont see that any debris got into the system.

I had a working compressor from a suburban that is the same compressor and I know is good. I am a bit confused on how to charge the system.

I bought a set of r134a manifold gauges and I am borrowing a buddies vacuum pump to evac the system. Does this remove the oil as well from the system or just the moisture and refridgerant?

I looked up that this system uses 8 ozs of pag 150 oil and 2.0 lbs or 32 ozs of R134a. Now Ive poured all the oil I can out of the "new" compressor and let it drain. Im confused on how much new oil to add to the compressor when I install it?

If would seem I would have to put the pag oil in the compressor and then evac. But how do I know how much oil is still left in the system? Do I pour in the ful 8 ozs ?

Im confused on the evac and flushing process. Does flushing with a flush product completly remove all oil from the system?

Thanks guys!

Body seal leaks on the HT6 are very common. That alone does not mean that debris has contaminated the system. Remove the fixed orfice tube and check the screen for debris. If there is no debris in the screen, don't bother flushing the system. The tube is inside the inlet line, (lower line), at the accumulator. Remove the high pressure line and remove the orfice tube. If the system has zero pressure for any length of time, it's a good idea to replace the accumulator. It has a desicant inside that absorbs moisture in the system and if exposed to atmosphere, it will absorb humidity. The desicant will absorb only so much moisture and after that, the accumulator must be replaced.

Evacuating will remove oil vapor, (not enough to worry about), moisture and refrigerant from the system. The system must be evacuated to 29.4"Hg, (2 atmosphere's) for a minimum of one hour before recharge, the longer the better.

If you measured the oil that was removed from the original compressor, drain the "new" compressor and add that amount plus 1 ounce. If you didn't measure it, drain the "new" compressor, install it on the vehicle, and add 8 ounces into the low side port on the compressor, connect the lines and turn the compressor shaft by hand at least 10 revolutions to circulate the oil into the system. Then evacuate the system, and recharge using the low side port on the accumulator. It's better to have too much oil rather than too little in the system. Too much oil will reduce cooling efficiency, too little oil will reduce compressor life.

Flushing compound will remove MOST of the oil from the system if done properly. It's impossible to remove all oil from the condenser and evaporator.

Thanks for the help. I drained the old compressor and added 1 more once to the new compressor so in all I ended up using about 4 ouncesof new pag 150. I then put 2 and a half 12 once cans into the system and it charged to about 35 lbs. It was blowing ice cold in the cabin and the head pressure was about 235 at max cold. Is there a way I can determine if there was no little oil in the system other than having a compressor failure?

Thanks!

There is no "dipstick" on the AC system ;) There is no way of knowing how much oil is in the system without draining each component. Oil must be measured when installing it. As mentioned earlier, you're better off with too much oil than not enough. 4 ounces might be a little low. Keep a close ear on the compressor, if it starts to make any abnormal rattle noises, add a couple more ounces and cross your fingers.

No noises so far. Im still a bit confused however. Can you clarify my thinking?

The system im working on holds a total of 8 ozs of oil total. When I drained the old compressor I got maybe 2-3 ounces out. So are the other 5-6 ounces still in the system? How much oil is lost when purging the mixed oil/refridgerant?

I didnt take the rest of the system apart. Just added the 4 ozs to the compressor, vacuumed and charged. If I put more oil in than the compressor had in it shouldnt I be okay? I guess I dont understand where all the oil is stored in the system and how it is lost.

There is no "crankcase" in the compressor. The entire oil charge of 8 ounces is distributed throughout the system with approximately half of it in the compressor. The other half is circulated in suspension with the refrigerant. A certain amount of oil is lost when there's a leak in the system. If there's a catastrophic leak, such as a blown hose, more oil will be blown out than there would be with a minor leak, like the seals on the compressor.

Ok I think I get it now. Ill keep my eye on the compressor. I may pickup a pag oil charge and put that in to make sure its got enough oil. Thanks old master!

Ok so the compressor seems to be working fine but my A/C is no longer blowing cold. Everything is holding pressure and no leaks. After awhile it stops working and later it will start again. Am I correct in thinking the oriface tube is plugged.

I guess I am getting paid back for being cheap. Anyways to flush the system and fix it right I was going to replace the orifice tube and accumulator. How exactly do I flush the system? I bought some a/c flush solvent today. Do I just pour it in the lines and blow it out or is there a better way. Thanks!

Anyone?

Sorry for the delay, (been on vacation). Need to have some data from you on this one... Engine at 2,000 RPM, A/C on MAX, windows and doors closed, what are high side and low side pressures when the compressor cycles on, and when it cycles off? Also need to know the ambient temperature and relative humidity.