Blowing Fuse for blower 82 300sd - PeachParts Mercedes-Benz Forum

Jeep Taylor · #1 11-30-2007, 06:11 PM

Trying to get the blower to work on sons car keeps blowing 25amp fuse. I hooked a jumper wire across fuse terminals and it started to melt the insulation on the jumper. I am new to the MB vehicles it is a 126.120 chassie do not know where to start on this problem. I do fine on my 97 Ford Powerstroke and wifes 05 Jetta TDI is still under warranty. Any help will be appreciated as of now I know of no reputable mechanic. Thanks in advance Jeep Taylor

Brian Carlton · #2 11-30-2007, 09:28 PM

Does the blower operate when you install the fuse?

Does the fuse melt in the middle or does it explode and burn?

MaydayMike · #3 11-30-2007, 09:52 PM

Mine's doing this too. but only occasionally. It will run fine for days, then it will just quit. My motor may be arcing at the brushes though, and shorting out. I had it apart a few weeks ago, and there's only 1/4" of brush left, and at least 1/16" groove worn in the comm!

Jeep Taylor · #4 12-01-2007, 05:39 AM

The blower operates for a few minutes the fuse gets extremely hot it did not explode but it looked like it burned up, glass was black inside. Checked the brushes and they were not worn down that much. I read on the forum about cleaning out the resistor under the p/b brake booster and also cleaning contacts for fuse #10 will do that Saturday and see what happens. Thanks Jeep

Brian Carlton · #5 12-01-2007, 08:09 AM

Quote:

Originally Posted by Jeep Taylor

The blower operates for a few minutes the fuse gets extremely hot it did not explode but it looked like it burned up, glass was black inside. Checked the brushes and they were not worn down that much. I read on the forum about cleaning out the resistor under the p/b brake booster and also cleaning contacts for fuse #10 will do that Saturday and see what happens. Thanks Jeep

This usually occurs when the blower is drawing too much current due to age and drag in the bearings. If you have a suitable ammeter (20A), you can test the blower for current draw..........but, when the fuse behaves as in the fashion described, it's the most likely culprit.

Jeep Taylor · #6 12-01-2007, 09:31 AM

Brian, what should the current draw be on the blower? I have a clip on amprobe but the lowest scale is 40amps. Do you think it will read correct? Jeep

Brian Carlton · #7 12-01-2007, 11:55 AM

Quote:

Originally Posted by Jeep Taylor

Brian, what should the current draw be on the blower? I have a clip on amprobe but the lowest scale is 40amps. Do you think it will read correct? Jeep

Don't know the blower's draw offhand, but, you're blowing a 25 amp fuse.........correct? Is the blower is the problem, the amperage will be right around that number........maybe a bit more.

A 40 amp full scale reading should be fine. See what it reads..........

Jeep Taylor · #8 12-01-2007, 12:21 PM

FUSE EATING 82 300SD. I cleaned out leaves etc from resistor under m/c,cleaned all fuse strips with wire brush and replaced fuses. Blower worked fine while car was parked ran it through all settings ie floor vents, defrost and all worked great till I drove it around the block. Took off from stop and under acceleration blower quit got home fuse was blown again. Anyone have a suggestion as to where to look for what I think is a short. Thanks Jeep

Brian Carlton · #9 12-01-2007, 12:33 PM

Quote:

Originally Posted by Jeep Taylor

FUSE EATING 82 300SD. I cleaned out leaves etc from resistor under m/c,cleaned all fuse strips with wire brush and replaced fuses. Blower worked fine while car was parked ran it through all settings ie floor vents, defrost and all worked great till I drove it around the block. Took off from stop and under acceleration blower quit got home fuse was blown again. Anyone have a suggestion as to where to look for what I think is a short. Thanks Jeep

Did you perform a current draw test on the motor..........or would you like us to just toss out ideas of what it could be?

If you don't want to bother with a current draw test, then just unplug the blower and take it for the same test drive. See if the fuse remains intact. This would then eliminate any other issues other than the blower. At that time, you can change the blower without the current draw test.........although I'd still do it.

Jeep Taylor · #10 12-01-2007, 03:50 PM

Brian, best I could do on amp meter was 9amps on high speed. Left climate control set on economy and drove around fuse is holding so far. I will pick up some more fuses tonight and see what happens. Checked the wire to tranny as best I could too cold to drag jack out just slid under found wire and switch made sure it was not rubbing on frame. Could it possibly be the a/c compressor is bad and pulling too many amps and causing the problem?Thanks Jeep

Flounder · #11 12-01-2007, 10:42 PM

Jeep:

Not sure if this is your problem, but my blower was also popping 25A fuses this week, so I pulled the motor this morning and sprayed WD-40 into both end bearings. I spun it a bunch by hand, then sprayed some more WD-40 on them. (my theory was that it would get pulled into the bearings by capillary action............I hope anyway)

I've driven it around a few times today and so far it hasn't popped the fuse yet.

Good luck.

Bert

Brian Carlton · #12 12-02-2007, 11:25 PM

Quote:

Originally Posted by Jeep Taylor

Brian, best I could do on amp meter was 9amps on high speed. Left climate control set on economy and drove around fuse is holding so far. I will pick up some more fuses tonight and see what happens. Checked the wire to tranny as best I could too cold to drag jack out just slid under found wire and switch made sure it was not rubbing on frame. Could it possibly be the a/c compressor is bad and pulling too many amps and causing the problem?Thanks Jeep

If the 9 amps is accurate, the blower is not the culprit.

I don't have the wiring diagram for the W-123, but, if the a/c clutch is on the same circuit, there is a remote possibility of a short in the clutch.......but, it typically draws only 3 amps, so, it would really need to be severe.

Leave it on economy for a few days (you don't need the a/c). If the fuse survives, then engage the a/c and see if you quickly lose the fuse.

airbus · #13 12-10-2007, 10:51 AM

On the '82 I recently bought, fuse #8 (blower motor, etc.) has been replaced already with a 25A. Since this really scares me, I replaced it with the original 16A. Guess what, melted away immediately. I figured I'd just put the (almost brand new and working) blower motor from the '84 in there: still melts. It works for a little while in 'low', but it immediately gets hot in 'high'. Any ideas? Could it be the resistor and how do I test it?

vstech · #14 12-10-2007, 12:02 PM

99.99999 % positive, it's the blower motor bearings. mine was melting the fuse holder, put a good used blower in there, no problems with the fuse since. of course, the blower I put in there has a mind of it's own... gotta get a new one in there.
the bearings are not replaceable, open cage ball bearings, gotta replace the entire motor.

airbus · #15 12-10-2007, 01:46 PM

I replaced the CCU (programa-*****) with my old one from the '84. Guess what: it works. Let's see how long the fuse holds...