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#46
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If the car is idle in 90F ambient air with the AC on, the fan should start fairly quickly. A few minutes at most. |
#47
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84 300SD - bought in April '06 with 237,000 mi |
#48
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#49
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I will do that tomorrow... What is the sure way to test operation of the condenser fan - Wire its plug directly to the battery? Where is the temp sensor that makes the fan come on?
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84 300SD - bought in April '06 with 237,000 mi |
#50
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Unplug the lines at the dryer and power it up there. If it doesn't start try jumping right to the fan. If it starts then you possibly have a bad relay. Danny
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1984 300SD Turbo Diesel 150,000 miles OBK member #23 (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination |
#51
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Jumper the pigtail leads that go to the red switch on the receiver/dryer.
Edit: dannym beat me by seconds!
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The Golden Rule 1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later) |
#52
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fan opperation
On my 91 350 SD ....they come on with the A/C.....You do need air flow across the condenser at idle...
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Ok, the receiver/dryer, as well as the high-pressure line going into the condenser, get pretty hot. Not so hot that I'd burn my hand by touching, but I wouldn't keep my hand on it for more than about 5 seconds, maybe.
Still, the condenser fan doesn't come on at idle. Quote:
So my question now is this. I am leaving on vacation down south tomorrow, and I don't have time to investigate this or replace the relay... Do I need this condenser fan on only when the car is idling? If so, then I probably don't need to worry because I will be doing mostly highway driving - it will probably get a good measure of fresh air without the fan. But I was also wondering if leaving those leads jumpered (fan always on) during this trip is a good or bad idea... Advice???
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84 300SD - bought in April '06 with 237,000 mi |
#54
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The fan on the SD only comes on when the refrigerant reaches a certain pressure. Since jumpering the connector ran the fan, I would guess it is your pressure switch. These are moderate failure items but I have replaced them. If I am remembering correctly there is a schrader valve that will allow you to change it out without losing refrigerant. The only consequence of it not coming on is higher evaporator temps at low speed and idle. I do not recommend wiring it on all of the time.
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D. Blake 86 300SDL 340K (for sale) 83 300SD 205K (gone) 06 Chevy K3500 LBZ CCLB 50K 94 Chevy K2500 6.5L TD 250K (gone) |
#55
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'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck. |
#56
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how the uninformed do it, not a suggested guide by any means
the '82 SD, compressor would run but minimal cooling - down from poor cooling last summer (Houston) R 12 per the connections so I bought some 2oz oil and 12oz cans; added most of the oil through the high side with difficulty, and then blew up a can of freon in 45°C water (impressive) - then added 2 cans in 45°C water through the low side (duh) w/o gages - now cools like a champ the '84 SD went from slight cooling last summer in So CA to zip here in Houston, but the compressor would run has apparently been converted to 134A but there are no stickers to indicate such and only the low side has a 134A 'adapter'; added 2 cans of 134A with oil using a cheapo low side (only) pressure gage, corrected for temperature - now cools, but nothing like the R 12 system - thinking I need to change it back but TX seems very anti-R 12 I was told one cannot get an insp sticker with R 12, but this seems to be untrue as I just got one for the '82
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Bill '82 300SD 195K '84 300SD 199K |
#57
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I stand corrected as it is a temperture switch that is on top of the receiver/dryer which turns the fan on. As per the manual it is suppose to kick in at 52C. I am not sure that it really matters as it is most likely still the problem. As I stated before, I can't remember if you lose refrigerant if change out. I don't think mine did. The manual also shows a temp switch for Aux fan to come on when coolant temp reaches 100C. In future I will leave this subject to the "experts"....
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D. Blake 86 300SDL 340K (for sale) 83 300SD 205K (gone) 06 Chevy K3500 LBZ CCLB 50K 94 Chevy K2500 6.5L TD 250K (gone) Last edited by D.Blake; 07-07-2006 at 03:15 PM. |
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Hm... Maybe my receiver doesn't reach 52C because the system isn't all the way filled with the refrigerant. I see refrigerant flowing turbulently through the viewglass, but there's lots of bubbles in the viewglass that are obvious during compressor operation. Someone said that when the bubbles go away, the system is full... I am no expert on that... But perhaps my condenser fan isn't kicking on if the system isn't completely filled?
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84 300SD - bought in April '06 with 237,000 mi |
#59
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Pete Burton is correct. Odds are you WILL lose refrigerant since most all of our older MB's have had the R/D changed to the newer style by now. The 9.5mm. switch is in contact with refrigerant. Because the P/T curve is mostly linear for R12 and R134a in the range we're discussing, MB switched to pressure switch from temp. The end result is ~ the same.
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1UE0YGZY61UE0YH47S&year=1984&make=MB&model=300-SD-002&category=R&part=A%2FC+Temp.+Switch Top picture is old style, bottom is new style (9.5mm.)
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The Golden Rule 1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later) Last edited by jbaj007; 07-07-2006 at 07:09 PM. |
#60
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FWIW, the R/D I have now has the 9.5mm threads. Not wanting to replace a perfectly good temp switch, I drilled and tapped a blind M6 hole in one of the 9.5mm threaded plugs, then screwed my original switch into it. Works fine.
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'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck. |
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