SL/R129: A/C problems :(
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mercedes
A/C problems :(
its getting real hot here in virginia and my A/C is deciding not to cut it in my SL500
if it isnt too hot out and i have parked my car in the garage, away from the sun, the A/C will blow cool
if it is more hot and especially if i have the car parked outside in the heat for a while, the A/C will do nothing and end up blowing the same temp as outdoors
my car has also been running slightly hotter than usual but nothing extreme, it hovers at 100*C and pokes above in stop and go, outside temps are 90+ so i think thats normal
thanks for the help
Hersh Singh
if it isnt too hot out and i have parked my car in the garage, away from the sun, the A/C will blow cool
if it is more hot and especially if i have the car parked outside in the heat for a while, the A/C will do nothing and end up blowing the same temp as outdoors
my car has also been running slightly hotter than usual but nothing extreme, it hovers at 100*C and pokes above in stop and go, outside temps are 90+ so i think thats normal
thanks for the help
Hersh Singh
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Your system is probably low on refrigerant. Maybe you have a leak. I'm guessing you don't have a set of pressure gauges, so you might try putting your climate controller into a mode where it displays the value of the inputs it is receiving. The step-by-step procedure follows.
1. Ignition to Position 2 with engine off or on.
2. Press the REST button and within 1 second press blower speed button 4.
3. The temperature window will alternately display an item number and its actual value.
4. Use the "F" and "C" keys to navigate to the different items.
02 = In-Car Temperature Sensor
04 = Outside Temperature Sensor
06 = Evaporator Temperature Sensor
08 = Heater Core Temperature Sensor
12 = Engine Coolant Temperature Sensor
14 = Temperature Selector Wheel Setting
18 = Vehicle Speed Signal (km/h)
20 = Soft Top OPEN ("u") or CLOSED ("o")
22 = Power Supply Voltage
83 = Not Used
84 = Blower Motor Voltage
Since you have an A/C problem, I would monitor the evaporator temperature, item #06. If your system is functioning properly, the values you read should fluctuate from roughly 4-8 degrees Celsius.
1. Ignition to Position 2 with engine off or on.
2. Press the REST button and within 1 second press blower speed button 4.
3. The temperature window will alternately display an item number and its actual value.
4. Use the "F" and "C" keys to navigate to the different items.
02 = In-Car Temperature Sensor
04 = Outside Temperature Sensor
06 = Evaporator Temperature Sensor
08 = Heater Core Temperature Sensor
12 = Engine Coolant Temperature Sensor
14 = Temperature Selector Wheel Setting
18 = Vehicle Speed Signal (km/h)
20 = Soft Top OPEN ("u") or CLOSED ("o")
22 = Power Supply Voltage
83 = Not Used
84 = Blower Motor Voltage
Since you have an A/C problem, I would monitor the evaporator temperature, item #06. If your system is functioning properly, the values you read should fluctuate from roughly 4-8 degrees Celsius.
Senior Member
Joined: Jul 2005
Posts: 265
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From: Manchester, UK
500 SL R129, Blue - 1991. Mini Cooper S, Works Kit Silver - 2007. Mitsubishi FTO, Silver - 1996.
Originally Posted by rellik
its getting real hot here in virginia and my A/C is deciding not to cut it in my SL500
if it isnt too hot out and i have parked my car in the garage, away from the sun, the A/C will blow cool
if it is more hot and especially if i have the car parked outside in the heat for a while, the A/C will do nothing and end up blowing the same temp as outdoors
my car has also been running slightly hotter than usual but nothing extreme, it hovers at 100*C and pokes above in stop and go, outside temps are 90+ so i think thats normal
thanks for the help
Hersh Singh
if it isnt too hot out and i have parked my car in the garage, away from the sun, the A/C will blow cool
if it is more hot and especially if i have the car parked outside in the heat for a while, the A/C will do nothing and end up blowing the same temp as outdoors
my car has also been running slightly hotter than usual but nothing extreme, it hovers at 100*C and pokes above in stop and go, outside temps are 90+ so i think thats normal
thanks for the help
Hersh Singh
2. If it still doesn't work top up the refrigerant.
3.If that doesn't work its probably the a/c unit that needs replacing.
I did step 1 and saved myself a fortune.
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mercedes
hmm, i did just replace my climate control unit with a refurb unit since my old one had non-functioning buttons
maybe it had corroded contacts, ill check that out
im scheduled to go in to recharge the system on wednesday, what should i expect the cost to be? hours of labor?
thanks
Hersh Singh
maybe it had corroded contacts, ill check that out
im scheduled to go in to recharge the system on wednesday, what should i expect the cost to be? hours of labor?
thanks
Hersh Singh
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Posts: 260
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From: US-Philadelphia
SL600
Probably minimal A/C design differences between 93 and 97 (although the control panel was different), but I just had the compressor and high side line replaced on my SL600. The compressor was groaning and the high side line was leaking.
My S500 just had the compressor, evaporator, and heater assembly replaced becasue it was doing exactly what you state. It could cool on mild days, but on the warmer days, the fan just blew at fullspeed all the time unable to keep up with the demand for cooling.
My S500 just had the compressor, evaporator, and heater assembly replaced becasue it was doing exactly what you state. It could cool on mild days, but on the warmer days, the fan just blew at fullspeed all the time unable to keep up with the demand for cooling.
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mercedes
i checked the evaporator temperature this morning
also i pulled no DTC's on the climate unit
the outside temp was 23 degrees C (75 degrees)
the climate unit was set to about the same as outdoor temp, the evaporator started at 21 *C and dropped to 8 after driving, at a stop light it moved back to 21 degrees after a few minutes
the next test i tried was to run the A/C at full cooling, the temp jumped from 6 dgegrees to 10 and quiclky rose to 20 at a stop light
due to what bobterry was saying this dosnt sound good, ill get it recharged tomorrow and see what happens
also i pulled no DTC's on the climate unit
the outside temp was 23 degrees C (75 degrees)
the climate unit was set to about the same as outdoor temp, the evaporator started at 21 *C and dropped to 8 after driving, at a stop light it moved back to 21 degrees after a few minutes
the next test i tried was to run the A/C at full cooling, the temp jumped from 6 dgegrees to 10 and quiclky rose to 20 at a stop light
due to what bobterry was saying this dosnt sound good, ill get it recharged tomorrow and see what happens
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Posts: 265
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From: Manchester, UK
500 SL R129, Blue - 1991. Mini Cooper S, Works Kit Silver - 2007. Mitsubishi FTO, Silver - 1996.
have you cleaned all the contacts yet... try a bit of thinned oil - wd40 on a cotton bud, and clean the connections from the car... if you have tried all these, its possible your new one isn't compatible...
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Thread Starter
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mercedes
got the system recharged, they threw some dye in there so i can check if it leaks down the road
it blows ice cold now though
are there any downsides to adding the dye?
thanks for all your help
Hersh Singh
it blows ice cold now though
are there any downsides to adding the dye?
thanks for all your help
Hersh Singh
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Posts: 4,054
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From: NJ
2009 SL63 AMG
Chilln. Yet another thing I love about the R129's is the sheer simplicity and directness of the A/C. It just blows cold air at you, that's all. My Dad's W220 and my Mom's W163 both have a newer style A/C which offer more options than one needs. Although the air circulation is a great feature on the W220, nothing beats the the raw simplicity of the SL A/C. And, if I really want cabin circulation, I'll just lower the soft top. 
