Cooling Fans and Compressor Questions
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1999 Mercedes-Benz C43 AMG
Cooling Fans and Compressor Questions
Hey, I have a 99 C43. I just had my a/c compressor and dryer replaced. Everything seems to working good. Its blowing freezing cold air now. I have a few questions though. When the a/c is turned on..are both fans suppost to come on full blast and stay on constantly? Also, is the compressor and cooling fans suppost to come on when the heat is on? Ive noticed my car doing this. I have read that by hitting the economy button, the compressor will kick off. Should I use this button what I am using the heat?
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190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
The a/c will come on when the interior controls are set to heat, it's to dehumidify the cabin air. Just leave the EC button off
As for the fans coming all all the time they will come on often but not full speed constantly unless it's very hot. First thing is to make sure your viscous coupling is working ok otherwise it may be a case of the aux fans making up for an inop main fan. What's the ambient temp when you're checking it?
Did you regas the system yourself? If the system wasn't vacced down sufficiently or the gas used was poorly handled previously (ie air in the bottle) then you will get very high condensor pressures which make the fans stay on all the time at full speed.
As for the fans coming all all the time they will come on often but not full speed constantly unless it's very hot. First thing is to make sure your viscous coupling is working ok otherwise it may be a case of the aux fans making up for an inop main fan. What's the ambient temp when you're checking it?
Did you regas the system yourself? If the system wasn't vacced down sufficiently or the gas used was poorly handled previously (ie air in the bottle) then you will get very high condensor pressures which make the fans stay on all the time at full speed.
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190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
Press and hold the "REST" button on the a/c panel until the display changes (about 6 seconds). Now use the fan speed buttons to move up and down the menu (value number is the on the left side).
Common values used are 1 interior temp, 2 ambient temp (raw value from sensor, not "dampened"), 3 heater core temp, 5 evaporator temp, 6 engine temp, 7 condensor pressure in bar, 8 condesoner temp.
Press the rest button again to exit the menu.
With the a/c on the lowest temp and fan on full and engine idling for 5 min, go the values 5, 7 and 8 and post what the pressures and temps are.
Common values used are 1 interior temp, 2 ambient temp (raw value from sensor, not "dampened"), 3 heater core temp, 5 evaporator temp, 6 engine temp, 7 condensor pressure in bar, 8 condesoner temp.
Press the rest button again to exit the menu.
With the a/c on the lowest temp and fan on full and engine idling for 5 min, go the values 5, 7 and 8 and post what the pressures and temps are.
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190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
Somethings not right there. Did you do this with the A/C system running on full cold? What ambient temp did you try this at?
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190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
Ok. Your first pontential problem is your evaporator temp sensor. If it's 50F out side and you have the A/C on full then it definately shouldn't be reading 80F. It may either be dislodged from it's correct location or faulty. The only issue this should cause is a potential to freeze the evaporator during a long trip and the compressor won't cycle on/off so it will increase fuel consumption.
Secondly for those ambient temps the condensor temps and pressure don't correlate correctly. http://www.glacierbay.com/ptchart134a.asp I would be guessing that you have a portion of air either in the system when it was charged (not vacced down sufficiently) or the gas that was used already had some air in it. When there is air in the system the condensor pressures go up rapidly but there is very little heat.
Secondly for those ambient temps the condensor temps and pressure don't correlate correctly. http://www.glacierbay.com/ptchart134a.asp I would be guessing that you have a portion of air either in the system when it was charged (not vacced down sufficiently) or the gas that was used already had some air in it. When there is air in the system the condensor pressures go up rapidly but there is very little heat.
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1999 Mercedes-Benz C43 AMG
hmm....that's interesting. Like I said, I just has my compressor replaced. Maybe the mechanics didn't vacuum it sufficiently. Where would you recommend I start at to try and get the problem fixed. I know you said it may be the evap temp sensor. Where is this located at? Should I just take it back to the mechanic and hope that he can find the problem?
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MBWorld Fanatic!
Joined: Jan 2007
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From: Sydney, Australia
190D 2.5 (x2), 190E 2.6, W202 C240,W202 C43 (C55), W210 E55, W212 E250CDI
Take it back to the mechanic, the refrigerant side of the system isn't right.
I'll have to check on the evap temp sensor, I've never had to change one. I know the W210 needs the dash removed but that may not be the case for the W202
I'll have to check on the evap temp sensor, I've never had to change one. I know the W210 needs the dash removed but that may not be the case for the W202
