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  #16  
Old 07-10-2010, 07:30 PM
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You need to put your car model and year into your signature..

So if you stop the engine and IMMEDIATELY restart.. the compressor will come back on?

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  #17  
Old 07-10-2010, 11:17 PM
LarryBible
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I have no intimate familiarity with the big bodied cars, but it sounds like jcciem might be on the money here. The reason I think this might be true is that you are getting condensation on the low side line meaning that the refrigeration portion of the system is cooling.

Another possibility COULD be a fresh air door open bringing in hot outside air, bringing up the vent temp.

These observations are based purely on theory with no intimate knowledge of your particular ACC system.
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  #18  
Old 07-11-2010, 12:55 AM
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Quote:
Originally Posted by werminghausen View Post
After some testing I found out that the compressor gets cut off after maybe 5-10 minutes of driving and once cut off it won't come back....unless I restart the engine.
This is typically a Klima issue. The Klima senses one of it's input parameters is not quite right and dumps the compressor clutch. The only way to get the compressor back is to shut down power to the Klima and reset it...........usually done by shutting down the engine.

My worst scenario was getting stuck in a heavy rainstorm in near 80 ambients. Water got onto the belt.........compressor slipped.........and the Klima dumped the clutch. Now I'm sitting in a steambath...............

Pull the Klima and jump sockets 5 and 7. This provides 12V directly to the clutch.........all the time. Drive the vehicle and monitor the vent temps. If they drop down near 40 and stay there, it's time to do Klima troubleshooting..........not a fun task, but necessary.
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  #19  
Old 07-25-2010, 04:28 PM
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Sorry for being so late:

I have a 1987 SDL and yes if I restart the car the compressor is back.
Yesterday I was driving for over an hour and the compressor worked well (well...is relative with 60F at the vents) then it stopped and didn't come back. So the time when the compressor is cut out is unknown to me. Sometimes it is after 10 minutes, another time after an hour. Martin



Quote:
Originally Posted by leathermang View Post
You need to put your car model and year into your signature..

So if you stop the engine and IMMEDIATELY restart.. the compressor will come back on?
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  #20  
Old 07-25-2010, 04:36 PM
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Hi Brian

I tend to agree that this is a klima issue. yesterday I was drivong for more than an hour before the compressor stopped working. So some of the parameter might be off...like the belt slipping what else might be the culprit.
However the one hour I was driving the compressor worked unfortunately with 55- 60 F temperatures. Temperatures won't come down even though I clamped the heater hose...but the monovalve seems to work just fine.
Bad flap? I removed the cover of the glove box and with the AC on I felt a warm airflow behind the glovebox when I put my fingers back there.. basically outside air (at 90F)
Do yo know what this means? Martin




Quote:
Originally Posted by Brian Carlton View Post
This is typically a Klima issue. The Klima senses one of it's input parameters is not quite right and dumps the compressor clutch. The only way to get the compressor back is to shut down power to the Klima and reset it...........usually done by shutting down the engine.

My worst scenario was getting stuck in a heavy rainstorm in near 80 ambients. Water got onto the belt.........compressor slipped.........and the Klima dumped the clutch. Now I'm sitting in a steambath...............

Pull the Klima and jump sockets 5 and 7. This provides 12V directly to the clutch.........all the time. Drive the vehicle and monitor the vent temps. If they drop down near 40 and stay there, it's time to do Klima troubleshooting..........not a fun task, but necessary.
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  #21  
Old 07-25-2010, 04:38 PM
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When my SDL did that I replaced the Klima with a simpler relay. I gave up the protection of the compressor speed sensor and 105/115*C (or whatever the actual setpoints are in an SDL) switch.

If you replace the Klima relay, consider one from a 300D 2.5, any year I think, which eliminates the 10 second compressor delay after starting the engine. I don't know electronics but I suspect it's that circuit that goes wacky in older Klimas.

Sixto
87 300D
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  #22  
Old 07-25-2010, 06:09 PM
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Sixto
interesting point: the klima relay from a 300D 2.5- does it fit in the SDL as it is?
And does it function the same- just without compressor delay compressor speed sensor and temperature cut out?

for instance 1990 300D 2.5
part number 0035456905

Kaehler (KAE)
AC Relay; AC Compressor Cut-Off Relay;11 Pin plus Locater Pin
Please verify appearance and Mercedes part number on existing unit prior to ordering. 1 per car $125?

Martin





Quote:
Originally Posted by sixto View Post
When my SDL did that I replaced the Klima with a simpler relay. I gave up the protection of the compressor speed sensor and 105/115*C (or whatever the actual setpoints are in an SDL) switch.

If you replace the Klima relay, consider one from a 300D 2.5, any year I think, which eliminates the 10 second compressor delay after starting the engine. I don't know electronics but I suspect it's that circuit that goes wacky in older Klimas.

Sixto
87 300D
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  #23  
Old 07-25-2010, 06:18 PM
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Checking the fresh air flap today:
I removed the glovebox inside and testes the fresh air flap function in the 3 ac modes. In defrost mode( left botton) the fresh air flap opens (flap coming toward the seat) and lets fresh air in. In the 2 other AC modes (second and third button to the left are closing the outside air flap (meaning flap pushes toward the engine closing the outside air off.
So I believe this is how it is supposed to be and the flaps can't be the reason for bad air temperatures at the vent?

However I was driving yesterday with AC on (55-60 degrees at vent) and had the glovebox cover removed. I could stick my fingers in and feel the temperature.
What I found was higher air temperatures (higher than 60 degrees) in the glovebox. It felt like outside air....but today I tested that it can't be outside air.
So what is this warm air inside the glove box?
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  #24  
Old 07-25-2010, 06:39 PM
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Quote:
Originally Posted by werminghausen View Post
Hi Brian

I tend to agree that this is a klima issue. yesterday I was drivong for more than an hour before the compressor stopped working.
Are you certain that the compressor was engaged during this entire time period? If the ETS is cycling the compressor, your results could be exactly as you observed.

The Klima issue won't resolve your vent temps if the compressor is operating.
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  #25  
Old 07-25-2010, 10:57 PM
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I agree that I have 2 problems:
1) the bad vent temperatures
2) the compressor gets cut off and won't turn on unless I restart engine

I am guessing that the compressor was not cycling on and off in 90F weather. I assume it is running constantly until it is cut off. But I can't tell 100%.
I was testing pressures and temperatures again today (car was in the driveway) and for the period of maybe 15 minutes the compressor was running constantly- no on and off cycle
I have also never experienced lower temps at the vents than 55-60 this year.
When the compressor gets cut off the air from the vents start smelling somehow (maybe moisture in the air) and I then from this point I see the temperature rising slowly from 60 to over 80F.

I agree that the klima relay would not solve the bad vent temperatures but it could solve the issue that something cuts out the compressor and it won't come on unless I restart the engine.

For the bad vent temperature I am still figuring out if it is
a) bad AC system
b) outside air infiltration
c) heater core infiltration ( at this point I assume that my monovalve
is working- so it is no c)




Quote:
Originally Posted by Brian Carlton View Post
Are you certain that the compressor was engaged during this entire time period? If the ETS is cycling the compressor, your results could be exactly as you observed.

The Klima issue won't resolve your vent temps if the compressor is operating.
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  #26  
Old 07-25-2010, 11:10 PM
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Quote:
Originally Posted by werminghausen View Post
For the bad vent temperature I am still figuring out if it is
a) bad AC system
b) outside air infiltration
c) heater core infiltration ( at this point I assume that my monovalve
is working- so it is no c)
a) You seem to have ruled out this issue after a proper fill with R-12 and correct gauge readings...........

b) Possible, but not likely to kill the vent temps to such a degree.

c) Clamping off the line to the heater core would rule out the monovalve. I do know that their check valves are not all that great and that the air from the system is always warmer than ambient.


The final possibility is a very poor evaporator. If the evap is nearly clogged with debris and dust, the heat transfer won't get the temperature down, even though the a/c system is working perfectly. Time to get a peek in there and see what you've got.

FWIW, the '86 gets down to 35F. in ambients below 80F. and will freeze its evaporator. Between 90F and 100F, the vent temp stabilizes at 40F. and the evap remains just above freezing. Inside the cabin gets downright cold...........
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  #27  
Old 07-26-2010, 07:29 AM
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Well, I have exchanged the evaporator 2 years ago and it should be almost brand new. if debris can get in there that fast?
I know there in no fine filter anywhere to keep leaves out.

Is there a way to 'easy' get access to the evaporator in order to take temperature measurement? I just want to make sure that the AC is working and then go from there.
Is there a way to get to the temperature sensor at the evaporator , take it out and stick a thermometer in? I forgot where this sensor was located.
I guess it was on the driver side way down....





Quote:
Originally Posted by Brian Carlton View Post
a) You seem to have ruled out this issue after a proper fill with R-12 and correct gauge readings...........

b) Possible, but not likely to kill the vent temps to such a degree.

c) Clamping off the line to the heater core would rule out the monovalve. I do know that their check valves are not all that great and that the air from the system is always warmer than ambient.


The final possibility is a very poor evaporator. If the evap is nearly clogged with debris and dust, the heat transfer won't get the temperature down, even though the a/c system is working perfectly. Time to get a peek in there and see what you've got.

FWIW, the '86 gets down to 35F. in ambients below 80F. and will freeze its evaporator. Between 90F and 100F, the vent temp stabilizes at 40F. and the evap remains just above freezing. Inside the cabin gets downright cold...........
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  #28  
Old 07-26-2010, 08:25 AM
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Quote:
Originally Posted by werminghausen View Post
Well, I have exchanged the evaporator 2 years ago and it should be almost brand new. if debris can get in there that fast?
Sorry..........forgot about that.

No, two years is not sufficient to accumulate enough dust and debris to clog the evap.............it takes more than 20 for that.

Back to the a/c system itself...............
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  #29  
Old 07-27-2010, 09:23 PM
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I have charged 1 can R12 tonight (ambient was 26C) and the pressure reading were not that different. What I realized was that the compressor started cycling on and off which didn't happen before. I got slightly better temperatures (around 50F) at the vents.
I'll wait until pressure equalizes and take the gauge set off and go for a spin.
I'll report back.
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  #30  
Old 07-27-2010, 11:23 PM
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I took the car for a spin and in the beginning it was all promising, cold air, ahh.
But soon the compressor was cut off and never came back. I restarted and... same thing. I am frustrated right now but maybe I need to get a new Klima relay from the 1990 300 D 2.5 ? in order to keep this compressor going.
Well the compressor never gets cut off when the engine is idling. So it must have something to do with the fact that the car is moving?

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