Question for the R4 compressor experts - PeachParts Mercedes-Benz Forum

mannys9130 · #1 02-22-2016, 11:45 PM

Quote:

Originally Posted by BillGrissom

Count me "wrong". My 1985 has a Sanden H13 on Rollguy's brackets. My 1984 has the R4 that came with it and will stay such because I have another used R4 (or 2?) plus a new R4. Both cool the same, best I can tell (given the quirky climate controls). Also "wrong" because I use Duracool hydro-carbon refrigerant and PAO 68 oil, which could be why my R4 lasts thru our severe Central Valley summers (>110 F).

Definitely. Hydrocarbon refrigerant's been beat to death already so I won't even attempt to touch that one... I'm glad to hear your Mk. 1 hand can't tell the difference between the two cars. My points still stand. Once you have to fuss with an R4, rip it out and put what's much better in its place. In Tucson, we see extreme temps that reach 115* F and subpar AC systems make themselves evident very clearly.

vstech · #2 02-26-2016, 11:43 AM

Quote:

Originally Posted by mannys9130

Definitely. Hydrocarbon refrigerant's been beat to death already so I won't even attempt to touch that one... I'm glad to hear your Mk. 1 hand can't tell the difference between the two cars. My points still stand. Once you have to fuss with an R4, rip it out and put what's much better in its place. In Tucson, we see extreme temps that reach 115* F and subpar AC systems make themselves evident very clearly.

I agree that the R4 is an inferior compressor... but it's been in use for decades, and the problems with it in this car are the car's design limitiations, NOT the compressors...

the biggest problems are the HUGE evaporator coil, and the massive interior and glass in the vehicle, and the minuscule condenser area in the car.

changing to a sanden will get you longer life out of the compressor... but if you want to use the R4, and you already have it... be SURE you address all the problems with the vehicles system.

start with a PERFECTLY CLEAN condenser... clean it inside and out. all fins need to be meticulously cleaned and straightened... or replace the thing with a new coil. flush the hoses, and clean the evaporator.

a filter in the line feeding the condenser would do very little, as filters are designed for liquid flow to clean... and there is no liquid flow before the condenser. the screen might catch some debris when the compressor grenades, but not worth the leak potential in my opinion.

now, protecting the TXV with a filter after the condenser is a great upgrade... no idea why the receiver doesn't incorporate a filter in it...

123/126 ac systems simply aren't gonna cool well stock without upgrades if the vehicle operates above 92F ambient... sanden or R4...
CERTAINLY not with 134 in them...

vstech · #3 02-26-2016, 07:00 PM

Quote:

Originally Posted by vstech

I agree that the R4 is an inferior compressor... but it's been in use for decades, and the problems with it in this car are the car's design limitiations, NOT the compressors...

the biggest problems are the HUGE evaporator coil, and the massive interior and glass in the vehicle, and the minuscule condenser area in the car.

changing to a sanden will get you longer life out of the compressor... but if you want to use the R4, and you already have it... be SURE you address all the problems with the vehicles system.

start with a PERFECTLY CLEAN condenser... clean it inside and out. all fins need to be meticulously cleaned and straightened... or replace the thing with a new coil. flush the hoses, and clean the evaporator.

a filter in the line feeding the condenser would do very little, as filters are designed for liquid flow to clean... and there is no liquid flow before the condenser. the screen might catch some debris when the compressor grenades, but not worth the leak potential in my opinion.

now, protecting the TXV with a filter after the condenser is a great upgrade... no idea why the receiver doesn't incorporate a filter in it...

123/126 ac systems simply aren't gonna cool well stock without upgrades if the vehicle operates above 92F ambient... sanden or R4...
CERTAINLY not with 134 in them...

remember... I did say clean the evaporator... you pointed out how much crud gets in there... but it's extra important to clean the heat rejection coil... the condenser. or the pressures build too high for the R4, and it disintegrates... black death.

ROLLGUY · #4 02-26-2016, 07:13 PM

Quote:

Originally Posted by vstech

but it's extra important to clean the heat rejection coil... the condenser. or the pressures build too high for the R4, and it disintegrates... black death.

That is another reason to have the condenser fan on whenever the compressor clutch is engaged. I designed the relay to do just that. Having the fan on right away gives the condenser a jump start, rather than having to wait for the thermal fan switch to turn on the condenser fan.