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aux fan not working with AC - help 400E W124
Hey guys. My A/C just starting acting up. The system is charged full, no leaks. I found when stopped or when in park, the A/c compressor cycle on/off/on/off/on/off etc etc. I suspect the low/high pressure switch is shutting down the compressor due to excessive high pressure. While driving, however, it works fine. I noticed my Aux fans no longer come on. The fuse is not blown. The red switch on the receiver drier is working. When I short the red switch terminals, I can hear a click in the fuse box from a relay. I took the relay apart and it looked fine. Its not a Klima relay but more so a standard issue relay with two big relays inside it. I dont suspect the problem to be there, should I? I know the aux fans work because they were just on today when my temp guage ran hot.
I have no idea where to go from here? Can anyone help me?
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
#2
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Look at the ceramic ballast resistor..the lead-in wire from the relay will MANY times melt & then that is inop...
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MERCEDES Benz Master Guild Technician (6 TIMES) ASE Master Technician Mercedes Benz Star Technician (2 times) 44 years foreign automotive repair 27 Years M.B. Shop foreman (dealer) MB technical information Specialist (15 years) 190E 2.3 16V ITS SCCA race car (sold) 1986 190E 2.3 16V 2.5 (sold) Retired Moderator |
#3
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Ok will do. This is the resistor that is in the general area of the receiver drier (drivers side front), correct?
Thanks for your fast response.
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
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Quote:
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
#5
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aux fans
now that you have found the resistor take a test light and with ac on check for power on both sides of it.you will find that either there is no power on one side[replace resistor]or that the wires on one end are cooked[should be enough slack available to repair] good luck david poole owner european performance dallas tx.
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#6
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Did you check the fuse on the relay (can't remember if it is blue or green). To access this you need to remove some screws to get to the second half the fuse box. See post #6 on this thread: 95 E300D high engine temp only with ac on. Replacing that fuse fixed my A/C for 2+ years. However recently I had a similar problem to what you are describing with my car. I checked that fuse and it was fine. AC was blowing warm, compressor would engage, but the aux fan would not come on. I changed the ceramic ballast resistor for fun and it didn't help. I took the car into the shop. It was low on "freon." They added some and the air cond. worked again. They added dye but could not find a leak. After that the car was in the shop for a couple of weeks to work on a glow plug issue. I picked up the car tonight. Turned on the AC and everything was fine. Drove for about 10 minutes and AC started blow hot air again! I stopped by the auto parts store and bought a pressure gauge. Seemed to be plenty of "freon" in the system. Drove home and parked it. About an hour later I started the car and turned on the A/C...cold air again and the low temp fans operated as normal. So there is a gremlin in there somewhere. My car is a 1995 E300D so I suspect the AC systems are the same... |
#7
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Thanks for all the responses guys. Im going to my mechanics later tonight and we are going to get to the bottom of this. From what I gathered, there is one resistor and two fuses (low and high speed fan). Since the high speed fan works, im guessing that the resistor is fine (i hope).
I will let you guys know my findings...
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
#8
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<
The resistor has nothing to do with high fan.. it is only used to drop the voltage for low fan... so, a bad resistor results in no low fan, but high fan is fine. |
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Quote:
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
#10
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#11
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found the problem
Well MB Doc was right on the money. The wire going to the resister looked like it caught fire and totally seperated from the resister terminal. Took about an hour to repair the connection (hard to get to). All is working now, and i got my cold A/C back in the city driving
Thanks to all you guys!
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93 300D 2.5 Turbo, Black/Palomino 273K 09 E350 Black/Black 41K |
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