Auxiliary fan fuse - PeachParts Mercedes-Benz Forum

radunegru · #1 09-08-2004, 02:16 PM

Mercedes 300E 2.8 1993
The 16A Fuse from the fuse box that is feeding the auxiliary fan (first stage) is blowing very often. Unitil today when it melts the housing completely.

I am doing a bypass with onother fuse(this time I will use a 20A one because I have read in some posts that the OEM 16A is too small. Am I doing a wrong think?
By the way, coud be any other cause of this fuse to blow?.
Just for your info: The aux fans work fine they are almost new.

Arthur Dalton · #2 09-08-2004, 02:37 PM

Usae an outside holder and good wire..
The 16 was fine for the single fan, but when they went with dual fans , they allowed upping to 25A...
The following year , they added the fuse to the top of the relay. like the low speed

radunegru · #3 09-08-2004, 04:35 PM

So You suggest that I shoud pt a 25A one.
Also what is the cause for heating and melting....maybe imperfect connection?

Arthur Dalton · #4 09-08-2004, 04:41 PM

Yes , connections and use .. That is why I would use a good exterior holder and new wires ..........
The dual fans spec is 25 amp draw , so that is why I would not be fearful of a 25A fuse [ plus that is what was later recommended on the later 124 E320 dual fan circuits w/fuse on relay modification..............

radunegru · #5 09-13-2004, 09:52 AM

I did installed a externnal fuse for aux fan ( stage I) whit the value 20A and it got melted down so the fan start only in second stage at 105 C cooling down to abot 90 and the cicle does not stop. I am very puzzeled by this . What coud be that burn the fuse ...Not only the fuse...the housing got melted too.

Arthur Dalton · #6 09-13-2004, 10:40 AM

>> the cicle does not stop. >>

What does this mean ??

Anyway, check the connections at the dropping resistor behind the headlamp.
I would also take an amp reading at the fans.
Lastly, they went with a smaller gauge wire on the low fan , and it did not work out, so you want to run a heavier one from the new fuse to the resistor.

radunegru · #7 09-13-2004, 10:54 AM

I am talking about going to 105 fan start in the second stage, cools down to 90 ang again and again the temp does not stabilize at 90 like used to be.
Also why the second stage work fine and the the fuse responsible to this does not melt? It is a separate circuit for the second stage?
How shoud I mesure the resistance at the fans?
What gauge of wire shoud I use and do you have any ideas where I can buy a ceramic housing( holder) for the fuse so it would not met again?
Thanks for prompt response.

Arthur Dalton · #8 09-13-2004, 11:10 AM

Quote:

Originally Posted by radunegru

I am talking about going to 105 fan start in the second stage, cools down to 90 ang again and again the temp does not stabilize at 90 like used to be.

OK
That means you have high fan , which is coolant temp sensed... so, my suspect is you have a bad thermostat or coolant problem...

<
That is correct .. there are 2 completely different circuits . The low fan uses a dropping resistor that I mentioned in my last post.. that , or the connections at it are suspect for that circuit.
The ONLY part that is common to these two circuits is the share the same fan motors.. other than that , they have seperate relays and fuses, along with sensors.
<
You measure their draw with an amp meter.

< Thanks for prompt response.

Larger than you have there now , preferably stranded copper.

Check the resistor circuit before u do anything , as that is the common weak link in the low fan circuit.
Also, be aware that the low fan is only energized when the a/c is on . that is what it is there for and is tripped by the a/c high side pressure switch... nothing to do with your coolant temp.

yjamous · #9 05-21-2005, 07:56 AM

Quote:

Originally Posted by Arthur Dalton

Usae an outside holder and good wire..

Hi Arthur
Can you please send me a link to a pictuer of an outside holder? I'm afraid the place of the auxillary fan has melted, and I might need to use something like that

I don't know what can be done about this.
And is the auxilary fan expensive? How much could it cost?

Many thanks