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  #1  
Old 07-12-2005, 01:17 PM
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Location: Atlanta, GA
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AC & aux fan

The compressor on my 1980 240D had a slow freon (R134) leak- been that way for years, so I would just add a can or two every summer. Last week I added a couple of cans, but while adding the second can the compressor started making more noise-was noisy anyway. Then it started cycling on and off and the aux fan stopped working. The next day I replaced the compressor and the receiver/dryer. The AC works great now, but the aux fan still won't come on. I have replaced all of the fuses in the fuse box (mostly for the hell of it), replaced the relays on top of the drivers side front wheel well and even replaced the AC temp switch that connects to the receiver/dryer, but the fan still won't come on. If I jump switch the fan where the fan wires connect to the AC temp switch it works just fine, so I know the fan is good. Does anyone out there know what else I should check/replace? While driving the temp guage stays just above the 80c mark where it always has.

All of the work above was done by my brother and me. He's a Toyota mechanic and had all of the correct equipment to do the work, so I know the work was done correctly. I have read a ton of previous posts on here, but couldn't seem to find one that offers a solution to this problem. Any help would be greatly appreciated. Thanks!

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1963 MGB
1972 300SEL
1980 240D
1989 300SEL
1995 E300D
2000 Audi S4

Last edited by jwduffey; 07-12-2005 at 02:52 PM.
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  #2  
Old 07-12-2005, 01:45 PM
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Did your brother inform you that when you have a "leak" and "just add another can of freon" that you are not adding ac oil at the same time? You eventually run out of oil which is what happened.

Good grief, no wonder the compressor seized.
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  #3  
Old 07-12-2005, 01:47 PM
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Check/replace the fan relay located on the left side fender. (its on the left side fender of my 300DT, your 240 may be different). Find one at a wrecker/pick your part place.
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Old 07-12-2005, 02:49 PM
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Compressor oil was added every other time freon was added (and we added oil to the new compressor as well). I have already replaced the relays but that didn't fix the problem
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1963 MGB
1972 300SEL
1980 240D
1989 300SEL
1995 E300D
2000 Audi S4
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  #5  
Old 07-12-2005, 03:21 PM
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You have to tell exactly what you did... otherwise people can't tell you what you may have done wrong.

Where did you add the R134a ?
Were you using the pressure guages to determine how much you put in ?
What were the readings ?
Were you feeding the refrigerant from the top or bottom of the container ?
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  #6  
Old 07-12-2005, 03:25 PM
LarryBible
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I hope you were using gauges and monitoring high side pressure. One of the things that causes problem in converted systems is the fact that the high side pressure is increased. It has to be monitored closely because it can easily "run away."

I suspect your high side switch might be your problem now if I understood your description correctly. Hook up your gauges and watch the high side pressure with an ohmmeter on the high pressure switch if the high side reaches about 290 and the switch has not made contact, replace it.

Good luck,
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Old 07-12-2005, 06:10 PM
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My brother used guages and some device that was supposed to remove all of the air out of the system. He was closely monitoting the guages- He has a pretty impressive set up. Where is this high side switch located? Is it the same thing as the AC temp switch? The fan stopped working with the old compressor and it hasn't come on since the new one was installed. I'll ask my bro to do what you suggested Larry and will post the outcome. Should the aux fan come on everytime the AC is switched on or just when it reaches a certain temp?

Also, Larry, I have been a member of this board for many years and always trust and look forward to your posts. I have learned a lot about my diesels from you. Thanks man!
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1963 MGB
1972 300SEL
1980 240D
1989 300SEL
1995 E300D
2000 Audi S4

Last edited by jwduffey; 07-12-2005 at 08:49 PM.
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  #8  
Old 07-12-2005, 06:15 PM
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Quote:
Originally Posted by Eric Eliel
Did your brother inform you that when you have a "leak" and "just add another can of freon" that you are not adding ac oil at the same time? You eventually run out of oil which is what happened.

Good grief, no wonder the compressor seized.
I'm sure he appreciated your post....
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  #9  
Old 07-12-2005, 06:26 PM
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inoperable aux fan

If you "jumped" the high-temp switch at the receiver dryer, and the aux. fan went on, then there are only two possibilities:

1) The new high temp. switch is faulty; or

2) the temperature of the refridgerant simply hasn't exceeded the threshold of the high temp switch.

If the aux fan relay was faulty, the aux. fan would not go on when you jumped the temp. switch, because the aux. fan would not be connected to voltage. Since the fan went on when you jumped the switch, it was obviously connected to power source, therefore relay was working.


Assuming that you put in an OE temp. switch, the temp. threshold at which the switch closes is designed for a R-12 system. As I understand it, R-134 will reach this temperature sooner than R-12, so the aux. fan should go on more often with an R134 system. So, as I said, either the switch is faulty, or you just havent reached the treshold temp. yet. Finbd out what the temp. threshold for the switch is, then take the switch out and heat it above that temp. and see if the switch "closes" (use a continuity tester or multi test meter to test for resistance).

Good luck,

Mark
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Old 04-18-2006, 06:40 AM
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Mark, excellent diagnostic path. The only problem with "take the switch out and test " is: so goes the R12. Most DIY people don't have the reclaimation equipment available to them. For this reason, when I converted my 83SD back to R12, and installed a new switch, I tested the switch before installing. We never want to believe new parts have the possibility of being bad, but in this case, it can be costly.
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  #11  
Old 04-18-2006, 10:06 AM
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Quote:
Originally Posted by Al Magaloff
Mark, excellent diagnostic path. The only problem with "take the switch out and test " is: so goes the R12. .
Not normally. Usually, the temp switch (unlike the pressure switch) fits into a receptacle on the receiver/drier which does not have direct contact with the refrigerant. Removing the switch won't vent refrigerant in most cases.

Aftermarket replacement parts may be different.

Last edited by tangofox007; 04-18-2006 at 07:04 PM.
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  #12  
Old 04-18-2006, 10:07 AM
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Quote:
The AC works great now, but the aux fan still won't come on.
It's not coming on because it's not supposed to come on.

Stop throwing parts at it and enjoy your nice cold air.

If your really that worried about it get your brother to shoot the ac line at the switch with an infra red thermometer and see if it's above 52C.

Danny
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  #13  
Old 04-18-2006, 10:15 AM
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Quote:
Originally Posted by jwduffey
Should the aux fan come on everytime the AC is switched on or just when it reaches a certain temp?
Only when the temp reaches a level high enough to close the fan switch. I have 134A in my 300D. It does not take much of a refrigerant loss before the fan never comes on.
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  #14  
Old 04-18-2006, 10:17 AM
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Quote:
Originally Posted by dannym
It's not coming on because it's not supposed to come on.
Danny

?????????????????????
Are you sure about that Danny...
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'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John
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  #15  
Old 04-18-2006, 02:28 PM
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Quote:
Not normally. Usually, the temp switch (unlike the pressure switch) fits into a receptacle on the receiver/drier which does not have direct contact with the refrigerant. Removing the switch won't vent refrigerant in most cases.
tangofox007,
The car's original R/D was that way, but for a LONG time all the R/D's have the aux. fan switch directly in contact with refrigerant, so it WILL vent on you. See the two types of switches here:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1RX11DXS31S60SQ6X8&year=1984&make=MB&model=300-SD-002&category=R&part=A%2FC+Temp.+Switch

The top picture is the factory original which works as you described, but rarely seen anymore due to some A/C service over the years on our older cars.. The new one is different thread size etc. for "new" R/D.

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