A/C questions

[Philsky]

I think it is about time to change or hopefully upgrade my A/C compressor. I have found that my 1996 6.5 suburbans A/C as gotten weak and started to leak, I know I have to replace it but I spend a lot of time in the desert and I would lie something more powerful. I was hoping some one out there might have an idea either after market or factory. Thanks for your time and help.

Phil

[Robyn]

The key to good AC operation is to make sure the system is in top shape.
Replace the compressor with a good quality replacement unit and also replace the accumulator. (Large silver can on the RH side firewall (LH Drive rigs)

Make sure the condenser is clean and that there is not a buildup of crap between the Condenser and the radiator.

If these systems are in good order and charged properly they will cool very well.

My 95 truck will deliver air at the vents at around 44 degrees on a 95 degree day.

This is charged with 134A and not a special refrigerant.

Be sure once you replace the parts that you add any lost refrigerant oil and then pull the system into a vacuum 29" for about 30 minutes to remove any moisture that finds its way in while the system is open.

Charging has some exacts but not having a scale to measure the refrigerant I usually run the thing while adding refrigerant until the air temps and the gauge pressures fall into spec then call it good.

Never had any issues with any systems of mine.

The 134A systems are not quite as good as the older 12 systems but when they are working properly will do the job well.

A new low side switch is probably a good idea too so that the system will cycle properly (little switch on the top of the accumulator)

Also I would replace the orifice tube in the evaporator (small little device that slides into the evaporator on the inlet hose port. This usually has a tab with which to extract it. The inlet hose must be removed first)

Now if you find a metric buttload of metal crap in the orifice tube screen I would be thinking seriously about flushing the condenser as well as the evaporator with flushing fluid.

The components of the AC system do not like dirt, moisture and metal running through them at all.

The little compressors are delicate and will self destruct quickly if the system is contaminated.

A lack of proper oil volume is a big contributor to failure too.
The refrigerant oil mixes with the refrigerant and basically "Fogs" through the system as the refrigerant changes state and lubricates the compressor.

Look over your hoses very well and if you see any areas where the rubber is crimped into metal lines that shows oil seepage, the line is probably leaking and this would be a great time to replace them.

The line "Harness" can be easily replaced as a unit for not all that much $$$$.

Once you have the system up and working, a cruise through with a "sniffer" to check for any leaks is a good idea.

New parts generally dont leak , BUTTTTTTTTTTTTTT it can happen.

Dont reuse any of the old O Rings on the fittings. They can and will fail once they have taken a set.

If the system is fairly new, like less than a year one can usually get by with reuse but the few pennies it cost for new rings is just plain worth replacing them.

On many of these rigs there is a pressure switch on the condenser that will tell the ECM of over temp/pressure and causes the engine to idle faster to help reduce temp/pressure in the system. Find this switch and replace it especially on a high miler. (usually on the RH side of the condenser near the top and is easy to get to with the grill removed.


The other item is one that most folks dont want to talk about.
The evaporator case can become filled with loose debris such as pine needles over time that causes reduced air flow.

If there is any issues now would be the time to remove the heater assembly and clean it out.

As far as upgrades go, these systems are designed to work as a system and the components are sized accordingly.
Replace any bad parts with a good quality "exact replacement item"

A larger compressor wont do much. the evaporator and condenser are sized to work together and the compressor is sized to be able to deliver the needed amount of refrigerant flow.

Also if you have a rear air unit, be sure its working properly too.
These have a nasty habit of stoppage due to a failed expansion valve.

Hope this material helps

Robyn

[GMC Hauler]

Also I would replace the orifice tube in the evaporator (small little device that slides into the evaporator on the inlet hose port. This usually has a tab with which to extract it. The inlet hose must be removed first)

Also if you have a rear air unit, be sure its working properly too.
These have a nasty habit of stoppage due to a failed expansion valve.

Robyn


Robyn,


You have talked about the upgraded orifice before. I looked on Napa's website and found this: http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=430&CatId=12&SubCatId=5

This shows that the automatic adjusting orifice tubes that i've heard you talk about are not for Suburban's with rear air. Can you explain?

Is there a upgraded expansion valve for the rear air? Is that on the rear unit?

I have the R114, the gage set and the vacuum pump. I may be moving back to the south, in which case, my AC needs to be top notch.