Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 09-19-2009, 10:53 PM
fruitcakesa's Avatar
Registered User
 
Join Date: Jun 2008
Location: Vermont
Posts: 1,143
Blowing fuse #8

The other cold, rainy night while driving home from a local soccer game, with lights and wipers on, heat and defroster and rear defroster on full blast by the time I got the 5 miles back, the blower fan had stopped operating. When I pulled the fuse cover I found # 8 fuse, a red 16 amp unit, had melted in its socket.
The next morning I replaced the fuse and tested the blower for a minute with just the key on and it worked fine.
Last night with just the lights and defroster running on the same drive, it occurred again. This time I smelled a hot electrical odor and sure enough, #8 fuse was completely melted to an unrecognizable lump!
According to the fuse box cover, that fuse controls the blower fan, AC comp and and idle stabilization?.
My AC belt is off so I assume that is not an issue, Idle stabization I am uncertain about but the blower fan has been in service.
The fan works at all speeds and makes no unusual sound or smells so I am at a loss as to where to begin to track this down.
Any direction will be much appreciated.
This is in my 81 240.

__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily
Reply With Quote
  #2  
Old 09-19-2009, 11:28 PM
tankowner's Avatar
You talkin’ to me?
 
Join Date: Dec 2007
Location: Columbia, MO
Posts: 907
You are experiencing the same problem I am. I believe the answer is with the aging blower motors on these cars that are drawing more amperage with age. See post #8 on this thread:

FINALLY GOT THE A/C WORKING!

I haven't had a chance to really do anything about this, but hope to at some point. Please, whatever you do, do not but higher amp fuse in to try and "solve" the problem - you run the risk of starting a fire and losing your car.

Let me know if you find anything. Good luck.
__________________
'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
______________________________________

"Back off, man. I’m a scientist” ~ Peter Venkman
Reply With Quote
  #3  
Old 09-20-2009, 08:40 AM
fruitcakesa's Avatar
Registered User
 
Join Date: Jun 2008
Location: Vermont
Posts: 1,143
Tank, yep that sure sound like my issue. I take it you still aren't running your blower. I really don't want to "blow" 500+ bucks for a new unit.
Anybody know how much of a job it is to get the blower out?
__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily
Reply With Quote
  #4  
Old 09-20-2009, 08:45 AM
Registered User
 
Join Date: Dec 2005
Posts: 417
From my experiences it is the blower motor. Some have replaced the brushes with ones they found at the hardware store. I didn't have any luck finding brushes, but found one at pull-a-part and all is well...for now.
__________________
Brad
1981 300TD - daily driver
1963 Chevy II
2001 F-250 7.3 Power Stroke
Reply With Quote
  #5  
Old 09-20-2009, 09:00 AM
toomany MBZ's Avatar
Registered User
 
Join Date: Nov 2006
Location: central Va
Posts: 7,820
Those blowers are pricy, I found one on a forum, runs fine.
Do a search on the 'net, someone makes a brush kit.
__________________
83 SD

84 CD
Reply With Quote
  #6  
Old 09-20-2009, 09:29 AM
Banned
 
Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
If you purchase the ceramic fuses instead of the plastic, the "melting into an unrecognizable lump" will be eliminated.

Whether the fuse actually melts due to excessive current draw is still open to discussion.
Reply With Quote
  #7  
Old 09-20-2009, 11:24 AM
Yak Yak is offline
Registered User
 
Join Date: Aug 2009
Location: San Antonio, TX
Posts: 1,711
I inherited evidence of an overheated fuse 8 from the PO(s) in my '83 300CD - no fuse, just scorch marks. At first I was pissed because I thought I had been scammed during the test drive because the A/C "worked" then. Then I was confused because the blower still worked even though fuse 8 was removed.

A little investigation through the service records showed that fuse 8 was replaced with a fuse saver (from the original owner's notes). The original owner (I'm #3) actually wrote down dates and mileage of each time fuse 8 blew.

The p/n for the "fuse saver" installed in my car is an MB harness A 126 540 3013. It shows up in EPC net in 124's and 126's but not in 123's. I think I read there was a TSB about it. It installs the strip fuse holder 123 540 0450.

My understanding of the correct routing is that it completely replaces fuse 8, so if you've got the mini-strip fuse box installed on the left front fender near the relay box you should not have a fuse in position 8.

From previous experience with a stuck wiper motor, it's not "excessive current" that overheats the fuse, since that would cause the fuse to blow unless it's faulty. It's a more complicated "excessive time near, but not over, the design limit of the fuse." By design, the fuse is supposed to be the weakest link and blow, but through corrosion or dirt it becomes a little high resistance heating element instead.
Reply With Quote
  #8  
Old 09-20-2009, 11:47 AM
Registered User
 
Join Date: Jan 2003
Location: Matthews, NC
Posts: 1,356
burned fuse holders and melted fuses (melted as opposed to blown) are usually the result of a bad connection for the fuses. If the blower motor were causing the problem, the fuse would just blow. At this point the fuse saver is the best fix.
When you have a fuse problem, look carefully at the fuse. There is a science to looking at a fuse to see what kind of problem you may have. If the fuse element looks like it just melted, then it was probably from excessive (but not a dead short) amperage draw. If the fuse element looks like it exploded and splatted material around it, it is probably a dead short. If the structure of the fuse is melted then it is caused by a bad connection at the fuse. You can have multiple problems but always start at any burned or melted conditions first. Fix them and then continue.

Paul
Paul's Auto Electric
__________________
84 500 SEL (307,xxx miles)
Reply With Quote
  #9  
Old 09-20-2009, 01:12 PM
fruitcakesa's Avatar
Registered User
 
Join Date: Jun 2008
Location: Vermont
Posts: 1,143
Quote:
Originally Posted by Brian Carlton View Post
If you purchase the ceramic fuses instead of the plastic, the "melting into an unrecognizable lump" will be eliminated.

Whether the fuse actually melts due to excessive current draw is still open to discussion.
Who sells ceramic fuses?
__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily
Reply With Quote
  #10  
Old 09-20-2009, 01:14 PM
Diesel911's Avatar
Registered User
 
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 50,968
I have read more than several times on this forum not to use the Fuses with Plastic Bodies (because sometimes the Plastic melts before the Fuse does); use the Ceramic bodied Fuses.
Next they recomend using only Fuses with Copper on them as the silver colored ones oxidize and create a resistance to current flow.

There is also othe Fuse issues due to the contact point; see pic. This Fuse looked good until I pulled it out.
Attached Thumbnails
Blowing fuse #8-zfuseb.jpg  
__________________
84 300D, 82 Volvo 244Gl Diesel
Reply With Quote
  #11  
Old 09-20-2009, 01:44 PM
tankowner's Avatar
You talkin’ to me?
 
Join Date: Dec 2007
Location: Columbia, MO
Posts: 907
Quote:
Originally Posted by fruitcakesa View Post
Tank, yep that sure sound like my issue. I take it you still aren't running your blower. I really don't want to "blow" 500+ bucks for a new unit.
Anybody know how much of a job it is to get the blower out?
That's right, actually, I'm not even running the car yet. I bought the car cheap, but knowing it needed a lot of work - so it has been parked and I am slowly rebuilding things. When I bought it the PO said that someone else who had come to look at it stated that the blower wasn't working, but he claimed he really thought that it had been working. I checked the fuse and found that the plastic around the fuse terminal holder was melted. I managed to get a new fuse in so that it was making connections and then the blower worked fine. All fuses in the box were the plastic type, I replaced them all with the ceramic body type (you can find them here at Fastlane - if you don't see them just do a search). None of the fuses were actually blown, but many of them were so corroded that they weren't functioning. In a couple weeks I am supposed to be picking up the parts car that came with the one I bought. I am holding off until then in hopes that the fuse box in the parts car is good. If so I will swap out and then try to do some testing with the multimeter to see how things look. Wha everyone else has said here is very valid - so I wouldn't invest $750 in a blower when the real problem could be bad contacts at the fuse. Start by buying enough fuses to replace them all with ceramic ones. When you replace, clean the terminal contacts. Then go from there. As long as you have the correct amp fuse in, you aren't running any risk of ruining anything (except maybe a cheap fuse). Good luck - I'd be interested in knowing how things go for you.
__________________
'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
______________________________________

"Back off, man. I’m a scientist” ~ Peter Venkman
Reply With Quote
  #12  
Old 09-20-2009, 07:08 PM
fruitcakesa's Avatar
Registered User
 
Join Date: Jun 2008
Location: Vermont
Posts: 1,143
I gots to get me some a them ceramic fuses!

__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 12:07 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page