ac/blower fuse - PeachParts Mercedes-Benz Forum

85chedeng300D · #1 02-09-2007, 10:24 PM

hello gentlemen, on my '85 300d, 123, the ac/blower fuse is always burning out and it appears i found out that it gets real hot when my ac/heater is on and already melted slot for this fuse. ac work fine with a new fuse, and i already installed a blue, 25 amp fuse which only requires a red, 16 amp fuse to keep it from burning out because if not, it only lasts less than 5 mins at max air. what could be the problem? any ideas?

Austin85 · #2 02-09-2007, 11:19 PM

A bad blower?

An electrical short somewhere...?

..

Jeremy5848 · #3 02-09-2007, 11:22 PM

Be careful! The fact that the specified fuse burns out means you have a problem somewhere in the climate control system. Something is drawing too much current and you need to find it before it causes damage to the car. Changing to a larger fuse is not a good idea.

To find the cause, separate the various things that operate from that fuse and measure the current that each one draws. All of them together should not add up to more than 16 Amps. One or more, however, is drawing too much current, which is why your 16 Amp fuse burns out. Once you know how much current each component draws, you can figure out which one is drawing too much current. Fix that one and you will have fixed the problem.

If you don't have the equipment or skill to do this test, get someone to help you. Forum members should also be able to help you determine how much current the various items should draw and how much is too much.

I advise not using the Climate Control system until you figure this out.

sixto · #4 02-10-2007, 12:38 AM

Sometimes that happens because the auxiliary pump is seized. Disconnect the auxiliary pump connector and see if the fuse still blows.

Sixto
93 300SD 3.0

86560SEL · #5 02-10-2007, 12:58 AM

I agree... using a higher amperage fuse is a key ingredient for a major blaze!

Quote:

Originally Posted by Jeremy5848

Be careful! Something is drawing too much current and you need to find it before it causes damage to the car. Changing to a larger fuse is not a good idea.

Jeremy5848 · #6 02-10-2007, 01:45 AM

Quote:

Originally Posted by sixto

Sometimes that happens because the auxiliary pump is seized. Disconnect the auxiliary pump connector and see if the fuse still blows.

Sixto
93 300SD 3.0

Given all of the discussion that has taken place here about seized aux pumps frying traces in the ACC pushbutton unit, I would not have thought that it would cause a 16 Amp fuse to melt without doing some other kind of damage. But you could be right. It is certainly an easy thing to check and, I admit, a new way to look at this problem.

vstech · #7 02-10-2007, 08:02 AM

My SD has no aux pump, and the blower will melt the fuse body. also, the fuse card calls for the blue 25 amp fuse.
now, I found that the fuse will stay good once I TOTALLY cleaned the clips and the hole in the clip that holds the fuse. also needed was to clean the ends of the fuse before installing it.
since I cleaned all this, the fuse has not melted or overheated at all.
however, the blower started squeeking, and now will not run while the engine is running... odd. when I turn on the key, the motor blows fine, but once I start it, the blower quits. I will pull the blower out of my parts car and inspect it throuroughly... then install it in my driver.
John

MS Fowler · #8 02-10-2007, 11:46 AM

Today, the blower fuse blew on my '82 SD. It had a 16 Amp in it, but the card called for 25 Amp. I replaced it with a blue one ( 25 Amp)

85chedeng300D · #9 02-10-2007, 11:55 AM

thank you all, gentlemen!

my heater works fine and blows really hot at max heat, is this possible eventhough the aux pump is seized?

i'll try to unplug the aux. water pump and see what happens. my blower would squeak whenever the acc is somewhat satisfied and switch the blower to slow speed, but no squeak at higher/faster speeds when its at max or windshield defrost.

vstech · #10 02-10-2007, 01:22 PM

Quote:

Originally Posted by 85chedeng300D

thank you all, gentlemen!

my heater works fine and blows really hot at max heat, is this possible eventhough the aux pump is seized?

i'll try to unplug the aux. water pump and see what happens. my blower would squeak whenever the acc is somewhat satisfied and switch the blower to slow speed, but no squeak at higher/faster speeds when its at max or windshield defrost.

that sounds like mine... be prepared for it to fail... when you need it most.
John