Photo step by step post showing a W123 evaporator removal (1983 240D and 1982 300TD) - Page 4 - PeachParts Mercedes-Benz Forum

sjh · #46 01-24-2011, 04:56 PM

Is there a similar post for the w124 or w126?

crazy4diesel · #47 03-28-2014, 09:26 PM

I don't think that Dave the OP of this thread, has logged on since last October, but I'm wondering if anyone knows if the broken bracket he describes in this wiki is available? Mine is also broken, it has a part number on it of 90 412 09 127 which I am not able to locate anywhere.

vstech · #48 02-26-2016, 12:45 PM

black death is microscopic aluminum particles mixing with the oil and bonding to the metal and rubber tubing. a liquid filter can trap the particles with all the dessicant surfaces of the filter media. the screen and mesh in the casing keeps the scrubbing action of the liquid in place. with gasses you only have the surface area of the screen to catch what passes through. they will certainly catch some stuff, but the liquid side will catch far more. to be effective on the vapor side, the filter would need to be the size of our air filters to function well. notice there are only two types of filter driers for refrigerant. Liquid, and suction... the suction side filters are to protect compressors from building up contaminants in the oil, and to break down acids that form. they are HUGE in comparison to the liquid filters, and they only have about a month of life in them before they need to be removed, or they plug up, and kill the compressor.

sure, a liquid filter would offer some protection from black death or debris entering the condenser... but a liquid filter scrubs the oil and refrigerant for the life of the system, and prevents it in the first place.

leathermang · #49 02-26-2016, 07:24 PM

Quote:

Originally Posted by vstech

agreed... but keep in mind... a clean evaporator will increase the load on the compressor and condenser... so like I said EVERYTHING needs to be clean. .....

A clean evaporator does not increase the load on the compressor and condenser.... were you typing too fast when you wrote that? you can correct that and delete this post if you want to...

For the same amount of cold going to the passenger compartment having a clean and thus proper functioning evaporator is the minimum and designed load by the engineers for a given heat load...
any lack of cleanliness or obstructions increases the load and run time of the compressor.

vstech · #50 02-26-2016, 08:27 PM

Quote:

Originally Posted by leathermang

A clean evaporator does not increase the load on the compressor and condenser.... were you typing too fast when you wrote that? you can correct that and delete this post if you want to...

For the same amount of cold going to the passenger compartment having a clean and thus proper functioning evaporator is the minimum and designed load by the engineers for a given heat load...
any lack of cleanliness or obstructions increases the load and run time of the compressor.

I see what you are thinking, but the better the heat transfer through the evaporator, the more heat entering the refrigerant, and the higher the suction pressure will be. The txv will alter refrigerant flow to allow a set superheat be PRESSURE will rise with a clean evaporator coil.

leathermang · #51 02-26-2016, 09:17 PM

Vstech, for the SAME amount of cooling output into the passenger compartment per period of time... a clean evaporator will be less work for the compressor....
You are not taking into account the fact that the compressor will cycle off when the ' pilot set temperature' is reached....

vstech · #52 02-26-2016, 09:55 PM

you are not taking into consideration that a clean evaporator will cool the cabin better...therefore, it will absorb more heat... the evaporator temp will be higher, the freeze switch will not activate, due to the higher amount of heat intake of the evaporator... that heat will cause more stress on the compressor and condenser.

if the condenser is not clean, straight, and ready for the excess heat... the lifespan of the compressor will not be long.
running the electric fan will assist with heat removal, but CAPACITY and SURFACE area are needed to reject it all.

leathermang · #53 02-26-2016, 10:04 PM

Vstech, To suggest that putting an ' obstruction ' to efficiency ( clogged fins on the evaporator) into a system designed for a certain working pressure and time engaged is harder on the compressor ( it was DESIGNED for that ) than a properly cleaned system does not make sense...
IF what you are saying is correct in the larger picture... they would have installed the dog and cat and human hairs on the input side of the evaporator at the factory....

vstech · #54 02-26-2016, 10:21 PM

Quote:

Originally Posted by leathermang

Vstech, for the SAME amount of cooling output into the passenger compartment per period of time... a clean evaporator will be less work for the compressor....
You are not taking into account the fact that the compressor will cycle off when the ' pilot set temperature' is reached....

think about it... a dirty evaporator will ice up, it will block airflow, and it will take much longer to cool the cabin.

with it clean, the system will absorb heat from the cabin much quicker, the system will cool better, but that rapid heat absorption has an effect on the compressor and condenser, via the pressure rise.

the COMPRESSOR is happy with a dirty evaporator... but it won't cool very well. when the evaporator is cleaned, and the txv is operating optimally, with proper charge quantity, and a clean condenser, the overall system is much happier.

it's a total system, changing one part affects the entire system, not just the changed part.

many times techs will say, the pressure is low, it must be a restriction... but a restriction will cause the head to climb... no... a restriction will cause the head to drop. because refrigerant will back up behind the restriction. everything affects everything...

vstech · #55 02-26-2016, 10:25 PM

Quote:

Originally Posted by leathermang

Vstech, To suggest that putting an ' obstruction ' to efficiency ( clogged fins on the evaporator) into a system designed for a certain working pressure and time engaged is harder on the compressor ( it was DESIGNED for that ) than a properly cleaned system does not make sense...
IF what you are saying is correct in the larger picture... they would have installed the dog and cat and human hairs on the input side of the evaporator at the factory....

ha... no... that's not what I'm saying.

I'm saying that if one side is cleaned, and not the other, you will have major issues.

cleaning JUST the condenser will aid the system in cooling ok, and will not stress the compressor...

cleaning JUST the evaporator, will drastically load up the compressor if there is damaged condenser...

I'm just saying don't focus on only one part of the system...

it's ALL gotta be serviced to work properly. but if you ONLY clean one side, clean the condenser. because it's the side that removes heat from the SYSTEM... the evaporator just removes heat from the cabin. and when the heat is pulled from the cabin, it enters the ac system and needs to be expunged.

leathermang · #56 02-26-2016, 10:38 PM

The evaporator is not going to ice up when it is clogged from hair for the same reason it does not when it is clean... that little ' pig tail ' connected to the ' temperature regulator' which is against the evaporator to sense it's temperature will shut off the compressor...

vstech · #57 02-26-2016, 10:39 PM

Quote:

Originally Posted by leathermang

Vstech, To suggest that putting an ' obstruction ' to efficiency ( clogged fins on the evaporator) into a system designed for a certain working pressure and time engaged is harder on the compressor ( it was DESIGNED for that ) than a properly cleaned system does not make sense...
IF what you are saying is correct in the larger picture... they would have installed the dog and cat and human hairs on the input side of the evaporator at the factory....

also... from the size of the components, I am dubious that anything was DESIGNED on the 123 or 126 ac system... more like cobbled together to appease the stupid americans that think ac is important... germans don't need no stinking ac... why do we?

ha.

it's like mb went... the rich americans need ac to be a luxury car, hey, GM... can you loan us some ac parts? and they stuck in what would fit the grill and made the cabin all fancy and automatic.

look at most american cars... the grill is designed around large condensers. heck, my standard cab pickup has 1/3 the cabin space, but 4 times the condenser space... cools better than any 123 could dream of cooling... massive blower massive airflow... massive condenser... sure it's designed to flood the suction line, and has a built in liquid bucket and a stupid orifice tube instead of a sophisticated TXV... but the thing works very very well.

vstech · #58 02-26-2016, 10:43 PM

Quote:

Originally Posted by leathermang

The evaporator is not going to ice up when it is clogged from hair for the same reason it does not when it is clean... that little ' pig tail ' connected to the ' temperature regulator' which is against the evaporator to sense it's temperature will shut off the compressor...

yes, it will protect the compressor... because ice starts forming, and the freeze switch cuts out the compressor before the ice builds up. but it also keeps the cabin from getting cool.

if the evaporator is clean, the freeze switch won't cut out the compressor, because the airflow through the coil is greatly increased... so the compressor runs longer, and the pressures build.

look, you're arguing with me while you are agreeing with me without knowing it.

vstech · #59 02-26-2016, 10:46 PM

Quote:

Originally Posted by leathermang

Vstech, To suggest that putting an ' obstruction ' to efficiency ( clogged fins on the evaporator) into a system designed for a certain working pressure and time engaged is harder on the compressor ( it was DESIGNED for that ) than a properly cleaned system does not make sense...
IF what you are saying is correct in the larger picture... they would have installed the dog and cat and human hairs on the input side of the evaporator at the factory....

and actually... in a way, they did design the system with dog hair, and leaves in mind... it's why they put in the freeze switch. to keep the evaporator from getting too cold when airflow is low, when cabin temps are low, or when dirt builds up on the surfaces.

leathermang · #60 02-26-2016, 10:47 PM

No one is suggesting it is not important for the condensor to be clean... that is the bottleneck of any AC system... air across the condensor...
what I am disputing is this :
"" clean evaporator will cool the cabin better...therefore, it will absorb more heat... the evaporator temp will be higher, the freeze switch will not activate, due to the higher amount of heat intake of the evaporator... that heat will cause more stress on the compressor and condenser."" --Vstech

the ' more stress' implies something bad when we are discussing poor longevity from R4 compressors..... but cleanliness everywhere fins are is less stress on the system designed for clean fins everywhere than leaving the fins of the evaporator dirty...