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#1
05-23-2006, 10:48 PM
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98 ML320 ac compressor help
Hello everyone. After a long hard iowa winter, I went to turn my AC on and the compressor is not engaging. The blower operates, and the engine stumbles a little when you press the AC button, but no compressor activation.
To go back to last year....I have always had a problem getting my compressor to engage. I stopped worrying about it when it got cold. Now, I really need some help. The compressor could be coaxed in the past(last summer) into activating after tapping( pounding lightly) on the fuse box.....I discovered this trick after a hot summer day of checking fuses with the engine on and AC running and slapping the fuse box in frustration.....anyway, so we made it through the rest of the summer slapping away at the fuse box....Now, I have no idea... My question is, is it possible for the actual fuse box(the board that all the fuses and relays plug onto) go bad? I have lifted the fuse box and checked wires underneath to see if there was a short somewhere but everything looked good....I have priced the fuse box board at $150, but before I start throwing money at things, I wanted to know if anyone had any thoughts... Thanks,
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1994 S320 131K miles 1998 ML 320 126K miles 1994 Blue C220 122K miles Im going to Grad School @ the University of Iowa Go Hawkeyes!!! 
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#2
05-24-2006, 08:14 AM
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The A/C compressor signal travels THRU the fuse box...that signal is generated in the AAM (all activity module). Loose or BAD connection at that connector for the A/C compressor is COMMON/
__________________
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
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#3
05-24-2006, 10:28 AM
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Thanks for the help - MB Doc!
That is good news, kind of....so that means I have the problem narrowed down to the fuse box...I just have a couple of questions....you mentioned the AAM, is that the big black thin box that mounts perpendicular to the fuse box board? Looks like the connectors for that are on the bottom. How would I check the connections?
I am getting ready to move back from Iowa to Houston, and that drive sure would be nicer with ac... Thanks in advance.
__________________
1994 S320 131K miles 1998 ML 320 126K miles 1994 Blue C220 122K miles Im going to Grad School @ the University of Iowa Go Hawkeyes!!!
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#4
05-24-2006, 12:31 PM
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The compressor wire goes thru connector "M/A" pin # 2, either a pink OR purple wire. look for bad connection...
The connectors are marked & plug into the BOTTOM of the fuse box..
__________________
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
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#6
06-04-2007, 11:14 AM
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Hey 1994c220 Did you fix your air ?
This is another thread with no conclusion.
Just wondering if you solved the problem. I intend to pull the fuse box tonight...and look at my connections for my non working air.
__________________
Steve Danville what i did myself. CPS rear shocks MAS x 3. SparkPlugs (twice) Fuel pump & Filter Window switch replaced both failed horns with Honda horns. Cleaned ERG Tube Oil changes Oil consumption Fix Brake Pads A/C Recharge Anti-Freeze change X 2. Front Shocks. Monroe. $90 Mercedes Warrenty Work: Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles
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#7
06-04-2007, 01:25 PM
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Yes, but disconnect your battery!!!!! there are some high voltage wires under there...
Yes there is enough spare wire so you can pull the entire relay box out...I think there are about 8 screws that hold the cover box and the relay box in...you need to take them all out...there is a warning on the box that warns of voltage, and thats why I did, of course on one of my cleaning ventures, I forgot to disconnect battery....I remembered after I had ac relay box out.... It is a good thing to check the ac before you put everything back....I left it out, hooked up the batt cable and turned the car on to check ac....of course that was before I ventured to removing the AAM box..
__________________
1994 S320 131K miles 1998 ML 320 126K miles 1994 Blue C220 122K miles Im going to Grad School @ the University of Iowa Go Hawkeyes!!!
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#8
06-04-2007, 01:27 PM
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Its not that bad....getting the AAM is the hardest part....after you get it off, clean the connections on the AAM and where it hooks up to the relay board!!! thats what fixed it for me...i used flat tip screwdriver to scrape the contacts clean too....but do it gently.
__________________
1994 S320 131K miles 1998 ML 320 126K miles 1994 Blue C220 122K miles Im going to Grad School @ the University of Iowa Go Hawkeyes!!!
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