Quote:
Originally Posted by Sugar Bear
ROLLGUY,
You are correct, good catch!
Thank you.
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You are welcome. This is for the newbees- Many (including myself) have learned the hard way. The standard DIY vac and charge on these cars may work once in a while, but for the most part, a couple weeks to a month at best. They most always have leaks, and the only reliable way to test is with pressure before a vac and charge. This is especially true with R134a. It has smaller molecules than R12, so a hose that might not have leaked with R12, will surely leak with R134a. Also, with the R4, there is NO OIL SUMP. When refrigerant leaks, the oil leaks with it. Often when a DIY recharge is done, a complete flush and proper oil charge is NOT part of the job. This oversight usually ends up in disaster for an R4. With no or very little oil circulating, the compressor will seize, and/or spread it's innards throughout the system. If a proper flush is not done BEFORE installing a new or rebuilt compressor, that compressor may not last long. Also, the old mineral oil that is left in the system is not compatible with PAG and R134a (used in most new/rebuilt compressors). It is imperative that all these steps be followed precisely if one desires their new compressor to last more than a month or season (at best).
Before deciding to go the Sanden route, I experienced all the bad scenarios that are possible with the R4. If one desires a long lasting A/C system in their 'Benz, follow these steps:
*If possible, leak check before removing/replacing any equipment
*replace any bad, or all old hoses and Orings
*flush all remaining hoses, evaporator, and condenser (Parallel Flow
condensers must be replaced, they can't be flushed properly)
*if DIY charge, add the proper type and amount of oil before installing
components. Dye is recommended for leak checking after charge
*install the new compressor noting what type and amount of oil came with
compressor
*if replacing expansion valve, be sure to replace with one compatible with
the refrigerant you are using
*replace receiver/drier, and leave capped until hooking the last two hoses to
it.
*check for leaks with dry gas, repair any leaks
*for pro charge, add the proper type and amount of oil with charge machine
and then charge with the proper amount of refrigerant (gauges with R134a,
sight glass with R12)
*check for leaks with UV light or sniffer (or both).
It is important to note what type and amount of oil is in the new/rebuilt compressor that is being used. If your compressor came with PAG (for R134a), and you are running R12, you MUST drain the compressor and flush the system, as PAG and mineral oils are not compatible. If you are not sure what oil is in your compressor, it is best to start "with a clean slate". Ester oil is compatible with both refrigerants, so that is what I use. The typical system needs 8 ounces of oil to work properly. If one does not know the amount of oil in their new compressor, or looses some upon installation (common with the ports being on the low side in a 'Benz), it is best to just drain the compressor, and add the proper amount of oil to the other components (or during the charge process). This way, you know that there is enough oil in the system. Even if draining the oil from the compressor, there is enough oil inside for start-up. The oil will then circulate with the refrigerant.