[R129 SL] Another air conditioning question

[Jan Kuylaars]

Peter .
 
I replaced the battery and enjoy the sun on the bike.
I heard the news yesterday about the big water flood in New Zealand.
What am I complaining about a gearbox, if some other people losses their
homes and relatives.
I hope the New Zealand government can help those people.
 
And then my mechanic told me that there was a possibility that my oil
filter is slipped tight .
I drove 40000 km with the car and I don't know if they ever had replaced
the oil and the filter.
If the filter is become dirty and the pump is making a lot off pressure,
he said, the oil can be pushed out of the system by the outlet.
It is strange that after I filled the gearbox and the pump is not
running anymore the oil level rises about 4 cm above maximum.
If the engine is running  the oil level go"s down.
 
So we will replace the oil filter and oil and gasket to see what happens
before we start bringing the car to the dealer.
Imagine that the dealer does this and give me a invoice for replacement
of the total gearbox.
 
And then, if the pump is with damaged bearings, it seems me to take a
revised gearbox for 700 euros more than to have problems again over 
one year .
 
Tomorrow driving the Venture again ( Or MAzda when it is raining badly)
Jan.
 

-----Oorspronkelijk bericht-----
Van: r129list-bounces at mbcoupes.com
[mailto:r129list-bounces at mbcoupes.com] Namens Peter Shelton
Verzonden: zondag 15 juli 2007 23:11
Aan: George Jenner; SL Mailing List
Onderwerp: Re: [R129 SL] Another air conditioning question


Hi George,
 
The 'on' coil temperature is the temperature in front of the evaporator
coil!  The 'coil' is a radiator looking part inside the 'clipped'
plastic aircon unit that is on the upper part of the dash but behind the
dash.  It is actually installed from the front of the engine bay in most
models (unsure of the 129 as I have not dismantled mine or any 129 for
parts as yet!).   If latent air (in the car or outside) is say, 20
degrees C (68 degrees F), then if the aircon is working on cold (set to
maximum temperature), the temperature 'off' the coil should be about 7
to 9 degrees.  It should only take about 3 - 5 minutes to start pumping
out cold air.
Set the car to air recirculation, and take the inlet to the aircon unit
(usually under the seats, and measure temperature, measure the coming
out of the front vents when both are set to coldest - should be about 7
- 9 degrees.  If you have a hotter day, the temperature should still be
similar ranges on the output, if it is working correctly!
 
I have my hard top stored in the 'top of the shed' and use the soft top
occasionally (when it is really raining hard).  I travel with the top
down, although the car does let water in even above 60 kph as Merces
need a rain deflector on the top of the screen. I travel with the top
down in all temperatures,  and just turn the heater on.  Just need a
warm hat, ears covered, side shields on my glasses and I'm off!  It is a
heck of a lot warmer (as Jan will confirm) driving the Merc in say minus
3 degree C temperatures, with the top down than being on the motorcycle
at the same temperatures (wind chill factor).  The bike is exhilarating
though and you do not have to lane queue as you can overtake easily with
care and not exceed the sped limit (100 kph on the 'open road' in New
Zealand). 
 
I do not use the aircon for cooling as with the top down it is nice and
breezy. If I want a tin top car, I use the Nissan Maxima, Toyota Echo,
Silver Bullet (1983 280E) or the Orange Roughy (1979 250 Carbie - gas
guzzler) if it is really cold or very wet.  I use the tin tops if the
cat comes with us, as she (the Siamese) has a tendency to jump out of
the 129!
 
Have a great day and good luck with the aircon.  Cold today and 'nearly
sleeting' in 'Eco City'. Jan (The Flying Dutchman and Vehicle Warning
Sensor Inventor) is enjoying the summer on the bike - have to make the
most of the fine weather!
 
Regards, Peter S. 

----- Original Message ----- 
From: George Jenner <mailto:gjenner at nc.rr.com>  
To: Peter Shelton <mailto:joyce.pm at xtra.co.nz>  ; SL Mailing
<mailto:r129list at mbcoupes.com> List 
Sent: Sunday, July 15, 2007 12:54 AM
Subject: Re: [R129 SL] Another air conditioning question

Hi Jan, thank you for the very fine and detailed procedure to check the
problem out.  I know that my fans come on and go off at odd times and I
can not tell where the control for the fans come from.  They never run
after I switch off the engine (like some other makes do) 
I would very much like to have the electronic circuit diagrams and the
diagnosis procedure my email is:
gjenner at nc.rr.com  - Peter, where do I check the on/off coil temperature
and what should I see when I check?  I get foam in the sight glass most
of the time.
 
George

----- Original Message ----- 
From: Peter  <mailto:joyce.pm at xtra.co.nz> Shelton 
To: SL Mailing List <mailto:r129list at mbcoupes.com>  
Sent: Friday, July 13, 2007 7:16 PM
Subject: Re: [R129 SL] Another air conditioning question

Hi Jan,  
 
Not good about your gearbox. I have spares for 201's and 123's but not
for a 129.  I bought a brand new 129 left headlight off "trademe" (NZ
equivalent of EBay) last week. Bought as an 'in case' spare.  genuine
part - $125 euros.  Amazing what people have in their sheds!
 
Jan, after 'frying' your gearbox, maybe you could call yourself the
"Frying Dutchman" rather than the "Flying Dutchman"!  It nearly sounds
the same?. 
 
One of our newer members in our NZ Mercedes Benz Club recently bought a
1974 350SL.  The fuel line leaked and the engine caught fire!   Did a
bit of damage but it was extinguished with a Fire Extinguisher.  It was
a dry powder (mica) type - what a mess it left and it is corrosive!
Also no insurance for this in NZ and he is an insurance agent/
investigator.  I have nick named his car "The Barbeque"  for obvious
reasons.  I suggest we all check our fuel lines frequently as perishing
fuel lines can be fatal.  
 
Jan, your description of the aircon is very good.  It is important to
measure the on/off coil temperatures as this gives an immediate
indication of where the problem may lie.  Bubbling in the accumulator
sight glass is also an indicator.  
 
Great sunny day in Eco City (Manawatu NZ).  The day started off at
minimum 2 and it is about 15 degrees now.  It is hot from the sun, as
the ozone layer over our country is depleting fast, and the UV filtering
effect of Ozone is nearly non existent.  Well, time for a ride in the
500SL, have to make the most of the sunny days. 
 
Regards, Peter S.

----- Original Message ----- 
From: Jan Kuylaars <mailto:J.kuylaars at kpnplanet.nl>  
To: 'SL Mailing List' <mailto:r129list at mbcoupes.com>  
Sent: Friday, July 13, 2007 10:30 AM
Subject: Re: [R129 SL] Another air conditioning question

George.
 
I am not a expert in AC, but basic working is that the compressor
compresses the gas to fluid and the fluid is giving of the heat that is
produced by compressing.
The front radiator is for cooling the heated fluid by passing air while
driving, or by air stream with the electric fans, during standing still.
The heated gas is pumped to the receiver drier to take out the moister.
After the drier there is a pressure control switch for shut down the AC
if the pressure is to low and a other for running the electric fans if
the pressure is to high.
 

If you system is not completely filled, you can see air bubbles in the
glass from the drier when the compressor is running. 
When you see no bubbles there is to less or no refrigerant.You can check
on the compressor. There should be a different in temperature in the
inlet and outlet
After the compressor stops , and there is a clear vision in the glass,
there is to much refrigerant in the system.
If the amount of refrigerant is perfect, the refrigerant should foam and
then stay clear after the compressor stops.
 

>From the drier the fluid runs to the evaporator inside the car , where

the fluid can expand to gas again, and for this expand the gas needs
heat.
The evaporator takes the heat from the room and the room becomes cool. 
 

>From the evaporator the gas is flowing back to the compressors low

pressure side, where the gas is compressed again to fluid and the
process starts again.
 
So as long as your car is driving and the radiator will be cooled there
is no problem.
When your car is standing still and the engine temperature is climbing
the problems starts;
 
There are in mine opinion two possibilities, I am not for sure , but I
am are trying to think with you :
First there could be  a failure in the basic operation, and the second
one is electronic problem from the regulation of he AC.
 
Lets start by the first: if your car is standing still and your electric
fans are not working, the fluid is not been cooled and the heated fluid
results in higher pressure .
Also there is a higher temperature in your evaporator. There is
expanding from the gas but it don't needs a lot of heat for this because
the temperature already is high. The result could be that the emission
of heat out of your car to the evaporator is gone. So no cooling.
This could be resulting in a spiral. After the pressure comes too high
the system shut down or the refrigerant will come out the high pressure
security valve.
Result to low refrigerant and not proper working of the AC.
 
Possible failure could be the fans, the fan control, the pressure switch
or the expansion valve which are not good operating with higher pressure
or heat.
 
Then there is a possibility for electronic failure , like the Italian
college told; The measure of inside temperature and outside temperature
in combination with the temperature from the engine. He told us to fix
this problem with a resistor placed in series with the engine
temperature sensor. Read the earlier messages.
 
Also there can be a failure in the circuit itself.
When you wish I can send you the electronic circuit diagrams and the
diagnose procedure.
 
Greetings from the standing still Dutchmen with damaged gearbox. 
 
I discovered on the bill from my garage that beside replacement from the
starter and the steering house, they replaced the rubber pipe from the
gearbox oil cooler because it should leak a bit. After that I only drove
40 miles before my gearbox looses oil with pump noise and burned oil on
the exhaust as result.
I must check if the rubber pipe is come loose, and maybe they are the
reason of no just oil level or other damage.
But then I have a problem if they are willing to confess and pay for the
damage.
 
Jan.
 
 
 
 
 
 
 
 
 
 

-----Oorspronkelijk bericht-----
Van: r129list-bounces at mbcoupes.com
[mailto:r129list-bounces at mbcoupes.com] Namens George Jenner
Verzonden: donderdag 12 juli 2007 15:59
Aan: SL Mailing List
Onderwerp: [R129 SL] Another air conditioning question


I have been experiencing a perplexing problem with my 1996 SL500 air
conditioning system.  I have the means to check the pressure on the
system and have noticed that when I first start the car the air
conditioned runs normally cold.  As I drive and the car heats up the
system runs normally, but if I turn off the engine (to gas up) and the
out door temp. is hot (in the high 90s) when I restart the car the air
conditioner is no longer running cold.  This has led me to check the
system pressure at various engine temperature stages and the pressure is
in the normal 40 - 50 range when the system is cooling normally but
jumps to 100 + when the engine is hot and the system no longer is
cooling.  I do not think I am loosing coolant but need help to locate
the problem.
 
Has anyone any idea of what may be causing this problem?
 
Thanks, George



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