current draw on blower fan

[John Schroader]

Recently got home after a couple of months working in NC. Included in the long list of things to fix upon my return was the blower fan in my wife's 300 SD. Seems that it melted down the 25 amp fuse. Replaced the fuse and the fan ran effortlessly (or so it sounded). Couple of hours later the fuse once again melted. I haven't had time to check into it any more, but would like to know the estimated current draw of a blower fan. I'm going to check the draw on this motor and either pull the fan or (if draw is OK) replace fuse with circuit breaker. Anyone know what the draw should be? Thanks.

[Oracle12345]

sounds like the brushes are worn down and drawing too much. When you are blowing fuses then its time to replace the motor

[DeliveryValve]

It's a common problem on w126's.

Here is are some discussion about it.

http://www.peachparts.com/shopforum/showthread.php?t=253697

http://www.peachparts.com/shopforum/showthread.php?t=144892


You'll need to bypass the original fuse socket with a fuse holder that is rated for 30 amps.

Here is the official MB add-on holder. Part number 126 540 30 13

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?header=header.jsp&footer=&product=1265403013&partner=mercedesshop&baseurl=http://catalog.peachparts.com/&clientid=catalog.mercedesshop









.

[Jeremy5848]

This same upgrade was done to the W124 cars. A healthy fan can draw as much as 28 amps.

[John Schroader]

Think I'll go with a 30 A ckt. breaker. Will pull the fan soon and check for tight bearings and worn brushes. Anyone know if the brushes can be replaced easily? And-------many thanks for the info.

[Diesel911]

Originally Posted by John Schroader

Think I'll go with a 30 A ckt. breaker. Will pull the fan soon and check for tight bearings and worn brushes. Anyone know if the brushes can be replaced easily? And-------many thanks for the info.

One of the members either replaced the brushes himself or had an electric shop do it. That info was in one of the fuse burning threads about 4 months ago.

[Jeremy5848]

Replacing the brushes is not terribly difficult although I don't know how hard it is to get the fan out of an SD. The problem seems to be finding brushes that fit and are not so hard that they wear out the commutator. Apparently Bosch does not sell brushes as a separate part and most American motor brushes are the wrong size. This has been discussed extensively in the forum, especially as regards 123s. I remember one such discussion in 2006 when I had my first 300D. In my case, the brushes were almost gone and the commutator was also badly worn down. I ended up replacing the motor.

[Hit Man X]

Yup, I just went thru this... and posted all my findings, per DeliveryValve's posting of my thread.

Fix it properly with the OE parts.

[John Schroader]

Installed the 30 amp breaker last night and now have a fan. Soon as time permits I'm going to go through the whole system. Something funny in the CCU that prevents fan from coming on unless I push the second button from the left (next to defrost). After I fire up fan with this button, can use other buttons for different settings. Too, fan only runs on 'high'. Not a high priority as long as I have a fan.

[Jeremy5848]

Originally Posted by John Schroader

Installed the 30 amp breaker last night and now have a fan. Soon as time permits I'm going to go through the whole system. Something funny in the CCU that prevents fan from coming on unless I push the second button from the left (next to defrost). After I fire up fan with this button, can use other buttons for different settings. Too, fan only runs on 'high'. Not a high priority as long as I have a fan.

Those symptoms scream "worn brushes and/or commutator." To your list of chores, please add "remove and inspect blower motor."

Jeremy