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#1
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240d blower motor fuse keeps melting
So recently I pulled apart my blower motor since it was making noise in the bearings. While I was lubricating the bearings I decided to overhaul the motor with new brushes and lubricate everything. After I reinstalled the motor I noticed that the number 8 fuse for the blower motor and AC compressor clutch kept blowing after a few minutes. After testing the blower motor on full blast and the AC knob in the off position it still kept deforming the fuse. So I am curious as to what could be making the blower motor draw so much amperage to blow a 25amp fuse. (I installed a blue 25amp fuse instead of the red 16amp fuse because the AC clutch would draw too many amps and blow the red fuse in a minute at most) Any thoughts appreciated!
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#2
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Trying to set the car on fire? Increasing fuse size is a great way to do it.
Put the 16A back in. Find the reason for the excessive current draw. If the clutch is drawing that much power, it's junk. Replace it before it burns your car down. Melting fuses rather than blowing fuses are usually due to overcurrent or a poor connection. The fuse boxes in these cars are notorious for poor connections with the fuses, try sanding the brass clips for the fuse with some sandpaper if it looks crusty. |
#3
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On a 240D the fuse holder #5 is not used. If the contacts on #8 are burnt try swapping the wires over to #5 *after you fix the issues*.
The fuse box drops down into the inside of the dashboard. The wires are long enough to lay the fuse box on the floorboard to work on it. Of course disconnect the battery first.
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The OM 642/722.9 powered family Still going strong 2014 ML350 Bluetec (wife's DD) 2013 E350 Bluetec (my DD) both my kids cars went to junkyard in 2023 2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles) 2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles) 1998 E300DT sold to TimFreeh 1987 300TD sold to vstech |
#4
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@diseasel300 Thanks sorry Im going to change it back to the original red fuse I value my classic Mercedes and I do carry a car fire extinguisher in the cabin as a precautionary measure and to save a life if the time ever comes. Also I'm using those plastic fuses can anyone give me a link to the proper ceramic ones please
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#5
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Quote:
Depending on where you are, some auto parts stores carry the ceramic fuses. I know Car-Quest here does. If no luck at the auto parts store, Amazon is another good source, you can get a decent quantity and keep spares in the glovebox. Only buy brass or copper element fuses, if the element looks grey or silver, move on. |
#6
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@Diseasel300 Thanks I'll go get some of those and I fixed the problem by cleaning the contacts with sandpaper and loosening the bolts on the blower motor housing a little to create less friction on the bushings/bearings and installing a red 16 amp fuse. I also had to push the connector for the compressor clutch down further on the connector since the wire under the clip was a little tight so I gave the wire more slack and made sure it was installed all the way down. I assume it shook loose from vibration, but nonetheless after a 15 minute test drive with the AC on full blast the blower motor and compressor never once stopped and I checked the plastic fuse when I got back and it did not deform whatsoever so success!! I will be replacing all fuses with the ceramic ones once I get my hands on some anyways thanks for the help!
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#7
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Never overlook the crusty connection. Any time you find something getting hot, treat it as corrosion or loose! Most of the time these blower fuse issues aren't the motor itself, it's just the connection with those crappy torpedo fuses!
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#8
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Quote:
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84 300D, 82 Volvo 244Gl Diesel |
#9
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By the Way I used to buy fuses for my US Cars at 99 cent and similar stores.
2 years ago I my Van died in traffic. I had it towed home and found the plastic body on the fuse in the run circuit to the coil had melted but the metal was still intact. From that time I replaced the fuses with better quality ones and have had no issues.
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84 300D, 82 Volvo 244Gl Diesel Last edited by Diesel911; 09-15-2020 at 12:32 PM. |
#10
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Ceramic Fuses
Most VW / Porsche shops / partshaus' will have the correct ceramic ones in stock cheaply .
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-Nate 1982 240D 408,XXX miles Ignorance is the mother of suspicion and fear is the father I did then what I knew how to do ~ now that I know better I do better |
#11
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I'm betting the blower is a dud. The bearings have probably worn out and its overdrawing. The only time I had trouble with the plastic fuses was when my blower motor did the same thing.
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2004 F150 4.6L -My Daily 2007 Volvo XC70 -Wife's Daily 1998 Ford F150 -Rear ended 1989 J-spec 420SEL -passed onto its new keeper 1982 BMW 733i -fixed and traded for the 420SEL 2003 Volvo V70 5 Speed -scrapped 1997 E290 Turbo Diesel Wagon -traded for above 1992 BMW 525i -traded in 1990 Silver 300TE -hated the M103 1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one 1979 Silver 300D "The Silver Slug" -Sold |
#12
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Yet if you don't have a fuse with a plastic body the body cannot melt before the metal strip does.
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84 300D, 82 Volvo 244Gl Diesel |
#13
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Exactly this. A failing motor that's drawing excessive current will cause the element to fail, not the fuse body. Heat from a poor connection is what makes the plastic fuses melt.
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#14
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W123 HVAC Blowers
I agree that the bearings are usually dry and have high friction, not that they're worn out per se ~
I've taken quite a few og them apart and after taking the extra time to fully clean out all the accumulated dust and dirt then soaking the oillite bushings before re assembling with new brushes I have noticed they turn by hand *much* easier and come on sooner in the Klima II equipped cars . If you're blowing / melting fuses and don't want to bother with the mess of fully servicing and 40 year old electric motor, just buy the $100 URO one, it fits and works .
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-Nate 1982 240D 408,XXX miles Ignorance is the mother of suspicion and fear is the father I did then what I knew how to do ~ now that I know better I do better |
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