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#1
06-30-2011, 02:33 PM
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A/C stopped working on 91 300d
Needing some help. A/C was working and then it just stopped blowing. I'm not a mechanic but what are some things I can check for to make sure it's not a simple fix. I checked fuses and they all looked okay. What would be the next thing to check.
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#2
06-30-2011, 03:38 PM
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Is the compressor actually turning ? Look to the inside front of the rotating clutch... front of compressor....if not turning.. then you need to check for loss of refrigerant...
Stopped blowing cold air... or stopped blowing air ? If air... then your blower may be need service.. or your control panel may not be sending signal to run the fan...
__________________
1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html Last edited by leathermang; 06-30-2011 at 03:51 PM.
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#3
06-30-2011, 04:44 PM
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Stop blowing completely. For a couple of weeks it seemed like it wasn't working well in that the A/C would be cold sometimes and then cool at other times. I thought it was having a problem keeping up with the southern heat. Could this be symptoms of the current problem?
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#4
06-30-2011, 04:47 PM
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I would search down the electricity to the blower... the blower can need new brushes.. info in cheap fix in archives on that..
put 12 volts with some test clips to see if it is capable of working.. low refrig does not affect the inside blower working.. so your AC may be just fine...
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1980 240d , chain elongation, cam marks reference: http://www.peachparts.com/shopforum/showthread.php?threadid=10414 http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html evap fin cleaning: http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator A/C thread http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html
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#6
06-30-2011, 10:00 PM
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Your car probably has a separate fuse for the blower motor. Check for a pillbox on the left/driver side suspension tower just ahead of the main fuse box. It will contain a 30A strip fuse.
Sixto 87 300D
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#7
07-01-2011, 12:43 AM
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I haven't had a chance to check the strip fuse yet but there is a new development. I decided to check the fuses in the main fuse box. I changed #7 as it seemed to have something to do with the climate control and fan systems. It didn't look bad but I figured I'd give it a shot. Well, I get in and try the system. Nothing happens. I then check all the settings, Auto, Max, Min...etc. etc. All of sudden it starts blowing again.
Now, I am sure the change of fuse is probably a coincidence as it didn't start blowing immediately but what do you make of it?
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#9
07-01-2011, 01:28 AM
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Second Circuit down in the List.
Zomezing is not right with your CCU (Climate Control Unit).
("'Mos Likely.") "Poor contact for the fuse." [As Sixto pointed out.] 1st thing to be done upon obtaining one of these 20 year old Chassis is to RePlace ALL the Old Fuses with NEW CERAMIC ones.(With Copper Contacts) Elsewise,They'll drive you batty! ALSO,In Electrical Matters "There Ain't No Coinkidences".
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'84 300SD sold 124.128
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#10
07-08-2011, 01:54 PM
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Ok, replaced the fuses, except for the pillbox one. Still looking for one.
A/C seems to work well when I first start up but on subsequent starts during same trip it loses cooling ability. Is it just a matter of the heat of the day? What could this be indicative of?
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#11
07-08-2011, 03:18 PM
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I'm still confused by your terms. Does the blower stop moving air or does the compressor not cool the air? If we've moved from the blower to the compressor, check for voltage at the low pressure switch. If there's voltage, the problem is likely with the Klima relay. If there's no voltage, the problem is with the PBU or evaporator temp sensor.
Sixto 87 300D
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#12
07-08-2011, 04:59 PM
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At this time, the blower is moving the air. At seemingly random times, the air is not cooled.
Today, as I was driving to get a replacement fuse, air was not cooled, then I get back in the car without doing anything except starting it and it is cooling like it should.
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#13
07-08-2011, 07:15 PM
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I checked the pressure switch and one of the connections was very loose. Cleaned the contact and re-attached the wire and at the very least the compressor kicked on. Now to test it a couple of days to see if that fixes the issue.
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#14
07-08-2011, 09:50 PM
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If it's the...
If it's the blower motor, I heard it could be the brushes on it, which you can get at a vacuum repair shop, though they'd have to be shaped to fit in.
I did a very thorough DIY post on this site. Send me money for all the time and effort I've saved you. 
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#15
07-11-2011, 09:45 PM
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Ugh, well, I thought it may be loose connections but apparently not. The only symptom that I see is that it cools properly after it hasn't been used for a couple of days. Today I switched it on and it cooled really well for about 30 minutes and then stopped blowing cool air. Any ideas?
To be clear, the blower/blower fan is squealing a bit but it moves the air just fine. Jbach36 - I'll submit your request to my CFO...but I don't think she will see it the same way.
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